JP3691920B2 - Magnetoresistive element and magnetic reproducing system - Google Patents

Description

【０１２４】
（実施例２）
サファイア基板のＣ面上、ガラス基板（コーニング社製＃０２１１）上、Ｓｉ基板の（１１１）面上に、厚さ１０nmのＣｕ下地膜を形成し、さらにその上にそれぞれ実施例１と同様の成膜条件でＣｏ₉₀Ｆｅ₁₀膜を形成した。なお、Ｃｕ下地膜は、バイアススパッタリング法やイオンアシストしたイオンビームスパッタリング法・蒸着法等で成膜できる。このＣｏ₉₀Ｆｅ₁₀膜の保磁力（Ｈｃ）を測定した。また、前記それぞれの基板上にＣｕ下地膜を介してＣｏ₉₀Ｆｅ₁₀膜の膜厚を種々変更して形成し、そのＣｏ₉₀Ｆｅ₁₀膜の保磁力（Ｈｃ）を測定した。その結果を図６に示す。さらに、前記基板上にＣｕ下地膜を形成せずに上記と同様にして種々の膜厚のＣｏ₉₀Ｆｅ₁₀膜を形成して、それぞれその保磁力（Ｈｃ）を測定した。その結果を図７に示す。
【０１２５】
図６および図７から分かるように、いずれの基板においても、Ｃｕ下地膜が形成されている場合（図６）は、Ｃｕ下地膜が無い場合よりも低いＨｃを示している。また、Ｃｕ下地膜の有無にかかわらず、サファイア基板のＣ面、Ｓｉ基板の（１１１）面、ガラス基板の順にＨｃが低く、良好であることが分かる。特に、サファイア基板のＣ面にＣｕ下地膜を介して厚さ８nmのＣｏ₉₀Ｆｅ₁₀膜を形成した場合に、８０Ａ／ｍ以下の低Ｈｃを示した。なお、Ｃｕ下地膜を有するＣｏ₉₀Ｆｅ₁₀膜のＨｃは、Ｃｏ₉₀Ｆｅ₁₀膜の膜厚増加にしたがって僅かに増加する傾向を示した。一方、Ｃｕ下地膜なしのＣｏ₉₀Ｆｅ₁₀膜のＨｃは、まず膜厚増加に伴い減少し、さらに膜厚が増加するにしたがって増加する傾向を示した。例えば、Ｃｏ₉₀Ｆｅ₁₀膜の膜厚が約８nmである場合、そのＨｃの極小値は１６０Ａ／ｍ以下であった。
【０１２６】
このように、基板上に強磁性膜を形成する際に両者の間に下地膜を形成することにより、良好な軟磁気特性を得ることができることが分かる。
【０１２７】
また、サファイア基板のＣ面上またはＳｉ基板上にＣｏ₉₀Ｆｅ₁₀膜やＣｏ膜を形成する場合の下地膜としてＣｕＮｉ合金膜を用いることにより、良好な軟磁気特性が得られることが分かった。また、ガラス基板上またはセラミック基板上にＣｏ₉₀Ｆｅ₁₀膜やＣｏ膜を形成する場合の下地膜として数〜１００nmのＧｅ，Ｓｉ，またはＴｉ膜を用いることにより、最密面配向が促進され、その結果、良好な軟磁気特性を得られることが分かった。
【０１２８】
また、Ｃｏ₉₀Ｆｅ₁₀膜やＣｏ膜より高抵抗である材料を下地膜に用いることにより、ＭＲセンス電流の分流を防ぐことができる。例えば、実施例１において記述したＮｉ酸化物膜は高抵抗であり、サファイア基板のＣ面上にエピタキシャル成長させることが可能な反強磁性膜であるので、下地膜と反強磁性バイアス膜を兼ねることができる。図８にＮｉ酸化物膜２６を用いたスピンバルブ構造の磁気抵抗効果素子を示す。
【０１２９】
（実施例３）
Ｃｏ₉₀Ｆｅ₁₀膜が示す保磁力に及ぼすサファイア基板の面方位の影響を調べた。本実施例では、Ｃ面およびＲ面（α−Ａｌ₂ Ｏ₃ 基板の（１０１２）面）で比較した。
【０１３０】
膜厚１０nmのＣｏ₉₀Ｆｅ₁₀膜をサファイア基板のＣ面とＲ面上にそれぞれ形成した。この面方位による結晶配向の違いを図９（Ａ）および図９（Ｂ）に示す。図９（Ａ）から分かるように、Ｃ面上では、良好なｆｃｃ（１１１）配向が実現でき、その結果保磁力が１６０Ａ／ｍ以下と良好な軟磁気特性を有するＣｏＦｅ合金膜が形成できた。一方、図９（Ｂ）から分かるように、Ｒ面上では、ｆｃｃ（１１１）のピーク以外にもｆｃｃ（２００）のピークが検出され、ｆｃｃ（１１１）配向があまり良好でない。このため、保磁力が数百Ａ／ｍ以上もあり、良好な軟磁気特性は得られなかった。
【０１３１】
図９（Ａ）において、Ｃ面では基板であるサファイアのピーク以外に２θ＝４３．５°付近にｆｃｃ相（１１１）面に対応するピークのみ（若干のｈｃｐ相（００１）面配向を含み得る）が強く現れている。また、このピーク強度が強いほどＣｏ₉₀Ｆｅ₁₀膜は低保磁力を示した。一方、図９（Ｂ）において、Ｒ面ではサファイアのピークおよびｆｃｃ相（１１１）面ピーク以外に、２θ＝５２．６°付近にｆｃｃ相（２００）面に対応するピークが現れている。このｆｃｃ相（１００）面配向の存在は、結晶磁気異方性容易軸が面内に現れていることを意味し、これは保磁力を上昇させる原因となる。
【０１３２】
次に、このサファイア基板のＣ面上におけるＣｏ₉₀Ｆｅ₁₀膜の（１１１）面（最密面）に対応するピークに関して、ロッキングカーブを測定した。そのロッキングカーブを図１０に示す。図１０から分かるように、θ＝２１．８°付近をピークとして半値幅が３°程度と極めて強い配向が確認できる。このロッキングカーブには、サファイア基板のピークも重複されているが、Ｃｏ₉₀Ｆｅ₁₀膜の良好な結晶配向が確認できる。
【０１３３】
次に、図１１に、Ｃｏ₉₀Ｆｅ₁₀膜の保磁力と、Ｃｏ₉₀Ｆｅ₁₀膜の（１１１）面（最密面）に対応するピークのロッキングカーブにおける半値幅との相関を示す。図１１から分かるように、ガラス基板上にＣｏ₉₀Ｆｅ₁₀膜を形成すると、（１１１）ピークが微弱である場合が多く、ロッキングカーブ半値幅は２０°以上であり、Ｈｃは３０００Ａ／ｍ以上であった。また、Ａｒ圧力、基板温度を最適化してロッキングカーブの半値幅が１５°程度になると、Ｈｃは１０００Ａ／ｍ程度に減少する。このＣｏ₉₀Ｆｅ₁₀にＡｌを約１％を添加した材料からなる膜をガラス基板上に形成すると、半値幅は８°程度に減少し、Ｈｃは３５０Ａ／ｍ程度となる。また、サファイア基板のＣ面上にＣｏ₉₀Ｆｅ₁₀膜を形成することにより、さらに半値幅は３°程度にまで減少し、Ｈｃは約１６０Ａ／ｍ程度となる。したがって、最密面（Ｃｏ₉₀Ｆｅ₁₀膜の場合（１１１）面）に対応するピークのロッキングカーブの半値幅が２０°未満に減少するに伴い、急激に保磁力が減少する傾向にあることが確認できる。例えば、ロッキングカーブの半値幅が７°以下で、保磁力が１６０Ａ／ｍと良好な値に近付いてくることが分かる。すなわち、Ｃｏ₉₀Ｆｅ₁₀膜の最密面配向が強くなっていくにしたがって、Ｃｏ₉₀Ｆｅ₁₀膜の保磁力が低下する。このように、良好な軟磁気特性は強磁性膜の配向度と強く相関があることが分かる。
【０１３４】
Ｃｏ₉₀Ｆｅ₁₀膜の最密面配向を強くする方法としては、上述したように、第１に後述する各種添加元素を加える方法、第２に基板材料・方位を選択する方法、第３に基板とＣｏ₉₀Ｆｅ₁₀膜との間に下地膜を設ける方法、第４にＭＢＥ等の超高真空成膜装置により成膜する方法等いくつかの方法が挙げられる。なお、第２の方法において、基板にサファイア基板のＣ面を用いた場合、その面をメカノケミカルポリッシュ、フロートポリッシュまたはイオンポリッシュ等で研磨して基板の平均表面粗さ（Ｒａ）を２nm以下にすることにより、その上に形成したＣｏ₉₀Ｆｅ₁₀膜がさらに良好な軟磁気特性を示すことが分かった。しかし、平均表面粗さが５nm以上では、Ｃｏ₉₀Ｆｅ₁₀膜の保磁力は１０００Ａ／ｍ以上であった。
【０１３５】
（実施例４）
実施例３において、Ｃｏ₉₀Ｆｅ₁₀膜の単層膜について、第１および第２の方法で最密面配向を強くすることにより保磁力が低下することが分かった。次に、Ｃｏ₉₀Ｆｅ₁₀膜を含む積層膜についても同様のことがいえるかを確認する。
【０１３６】
ガラス基板上にＡｌ含有Ｃｏ₉₀Ｆｅ₁₀１０nm／Ｃｕ５nm／Ａｌ含有Ｃｏ₉₀Ｆｅ₁₀１０nmの積層膜を実施例１と同様の成膜条件で形成した。この場合のＣｏ₉₀Ｆｅ₁₀膜中のＡｌ元素添加量とＣｏ₉₀Ｆｅ₁₀膜の保磁力との関係を図１２に示す。図１２から分かるように、積層膜においてもＡｌ元素の添加により保磁力を低下させることができることが分かる。また、実施例２に示した第２から第４の方法でも同様に積層膜におけるＣｏ₉₀Ｆｅ₁₀膜の最密面の配向を強くすることができた。
【０１３７】
次に、積層膜におけるＣｏ₉₀Ｆｅ₁₀膜の保磁力の最密面ピーク強度依存性を図１３に示す。図１３から分かるように、単層膜の場合同様に最密面ピーク強度が大きくなるほど、保磁力が低下しているが確認できる。上記構造の場合、ピーク強度は１０² （a.u.) と弱く、保磁力は１０³ Ａ／ｍ程度である。この場合において、Ｃｏ₉₀Ｆｅ₁₀にＡｌを１原子％程度加えた材料からなる膜を用いることにより、保磁力は数百Ａ／ｍ程度に低下した。また、ガラス基板をサファイア基板のＣ面に代えることにより、１０³ （a.u.) 以上のピーク強度と１００Ａ／ｍ以下の良好な保磁力が得られた。なお、このときの半値幅は７°以下であった。
【０１３８】
（実施例５）
Ｃｏ₉₀Ｆｅ₁₀にＡｌ以外の添加元素を加えて保磁力を調べた。この場合、添加元素として、Ｔａ、Ｐｄ、Ｚｒ、Ｈｆ、Ｍｏ、Ｔｉ、Ｎｂ、Ｃｕ、Ｒｈ、Ｒｅ、Ｉｎ、Ｂ、Ｒｕ、Ｉｒ、Ｗを用いたときにも保磁力の低下が認められた。また、それらの元素の組み合わせ、例えばＴａとＰｄ、ＮｂとＰｄ、ＺｒとＮｂを添加しても保磁力の低下が確認できた。一例として、Ｔａ含有Ｃｏ₉₀Ｆｅ₁₀１０nm／Ｃｕ５nm／Ｔａ含有Ｃｏ₉₀Ｆｅ₁₀１０nmの積層膜の構造において、Ｔａの添加量と保磁力との関係を図１４に示す。図１４から分かるように、この場合においてもＴａ元素の添加により保磁力が低下したことが確認できる。
【０１３９】
（実施例６）
以上はＣｏＦｅ膜に関して（１１１）高配向を実現した実施例であるが、ＣｏＦｅ膜に限られず、ＣｏＦｅＮｉ膜、ＣｏＮｉ膜等を用いても同様な効果が見られた。その実施例を下記表２に示す。表２は、（１）強磁性膜の組成、（２）基板の種類、（３）基板とスピンバルブ膜との間の下地膜をパラメータとして作製した図１と同様の構造（ＦｅＭｎ膜と接する側はＣｏＦｅ膜のままである）を有するスピンバルブ膜における（１１１）ピークのロッキングカーブ半値幅△θ₅₀、容易軸方向のＨｃ、△Ｒ／Ｒを示したものである。比較のため、表２と同じ組成の強磁性膜のスピンバルブ膜を下地膜なしにガラス基板上に作製した場合の結果を表２に併記する。
【０１４０】
【表２】

【０１４１】
表２から分かるように、ＣｏＦｅ膜に限らずＣｏＦｅＮｉ膜やＣｏＮｉ膜でも、ガラス基板への直接成膜に比べて、サファイアＣ面基板上あるいはＴｉ，Ｓｉ，Ｇｅ等からなる下地膜を用いることにより、△θ₅₀＜７°の良好な（１１１）配向膜を得ることができ、その結果Ｈｃが低下し、高い抵抗変化率が実現できる。
【０１４２】
しかし、Ｔｉ等からなる下地膜やサファイアＣ面基板により（１１１）高配向の（Ｍ 1nm厚／Ｃｕ 1nm厚）₁₆人工格子膜を作製したところ（Ｍ：Ｃｏ₂₀Ｎｉ₈₀、Ｃｏ₂₀Ｆｅ₁₅Ｎｉ₆₅）、△Ｒ／Ｒは２％以下の著しく小さな値を示しRKKY的反強磁性結合特有の高い飽和磁界が消失した。（１１１）配向するとRKKY的反強磁性結合が得られないので抵抗変化率が低下したことが分かる。したがって、スピンバルブ膜に限らずRKKY的な反強磁性結合を用いないタイプ（保磁力の差を用いたいわゆる非結合型人工格子膜（第１４回日本応用磁気学会学術講演概要集、1990年、177 頁）等）で（１１１）高配向を実現すると高い抵抗変化率と良好な軟磁性が両立しやすい。
【０１４３】
また、これに加えてＦｅＭｎに接する強磁性膜も下側磁性膜と同じ組成の膜に置き換えても同様の効果が得られることが確認された。
【０１４４】
（実施例７）
ガラス基板上（下地膜なし）にＴｉ５nm／ＦｅＭｎ８nm／ＣｏＦｅ８nm／Ｃｕ２．２nm／強磁性膜８nmのスピンバルブ膜を実施例１と同様の条件で成膜した。このとき、下部強磁性膜に加える非磁性添加元素と容易軸方向の抵抗変化率とＨｃの関係を下記表３に示す。
【０１４５】
【表３】

【０１４６】
表３から分かるように、ガラス基板に成膜した非磁性元素を添加しない膜に比べてＨｃが低下した。Ａｌ，Ｔａ等の添加ではＨｃの低下が顕著であるが、大量に添加すると抵抗変化率が大幅に低下した。Ａｌでは６．５原子％未満、Ｔａでは１０原子％未満で、ＮｉＦｅからなるスピンバルブ膜を上回る５％以上の抵抗変化率と低Ｈｃを両立できることが分かる。なお、ＣｏＦｅにＡｌまたはＴａを添加すると、Ｘ線回折において最密面ピーク強度が増加した。一方、Ｃｕ，Ａｕ，Ａｇ，Ｐｄ等は、Ｈｃ低減効果がＡｌまたはＴａほど顕著ではないが、１０原子％以下の大量の添加でも抵抗変化率の低下が見られない。ＣｏＦｅへのＣｕ，Ａｕ，Ａｇ，Ｐｄ等の添加でもＸ線回折における最密面ピーク強度が増加した。これらＨｃの低下には、Ｘ線回折における最密面ピーク強度が添加元素により向上したことから、前述した結晶配向性の向上が起因していると考えられる。これに加えて、添加元素による結晶磁気異方性の低減もＨｃの低下に起因している可能性もある。
【０１４７】
さらに、６５℃９５％ＲＨの恒温恒湿槽に１００時間放置して単層の各強磁性膜（１００nm厚）について耐食性を調べたところ、Ｐｄを７原子％以上添加した膜では変色はなかったが、非磁性元素を添加しないＣｏＦｅ膜、Ｃｏ₂₀Ｎｉ₈₀膜、Ｃｏ₂₀Ｆｅ₁₅Ｎｉ₆₅膜やＡｌを６．５原子％添加した膜、Ｔａを６原子％添加した膜等は変色が見られた。すなわち、Ｐｄの添加は、耐食性を改善する効果を発揮する。Ｐｄのみの添加ではＨｃの低下があまり顕著ではないが、Ｐｄを例えばＣｕと共に添加すると、高い抵抗変化率と耐食性を保って軟磁気特性のさらなる改善が可能になる。さらに、サファイアＣ面基板やアモルファス金属下地膜、ｆｃｃ格子の下地膜を用いると、Ｐｄのみの添加でもＨｃが８０Ａ／ｍ未満にまで低下し、さらに、Ｐｄの４０at％までのＰｄ濃度範囲で〜１０％の高い抵抗変化率を示した。しかしながら、同じ貴金属で耐食性改善に効果的であると予想されるＰｔを添加すると、ＨｃがＰｔを添加しない膜以上に増加した。このため、軟磁気特性の観点からＰｔの添加は好ましくない。
【０１４８】
（実施例８）
表面粗さがＲ_a ＝２nm以下の熱酸化Ｓｉ基板表面をＳＨ（硫酸と過酸化水素の混合液）処理により清浄化した後、この基板を真空装置内に載置して、１×１０^-9Torr以下まで排気した。真空装置内の水および酸素は、質量分析器および露点計によって管理した。以上の手順が終了した後、装置内に超高純度Ａｒガスを導入して、装置内の真空度を１×１０^-4Torrとし、ＥＣＲイオン源内部において２．４５GHz のマイクロ波放電を発生させて加速したイオンビームによりスパッタリングを行い、図１５に示すように、熱酸化Ｓｉ基板１５０上に第１の下地膜１５１として、非晶質Ｓｉ膜を膜厚５nmで成膜した。その後、真空を保ちながら連続して、第１の下地膜１５１上に第２の下地膜１５２として、Ｃｕ−Ｎｉ合金を膜厚２nmで成膜した。
【０１４９】
その表面に第１の強磁性膜１５３としてＣｏ₉₀Ｆｅ₁₀合金膜を厚さ８nmで、非磁性膜１５４としてＣｕ−Ｎｉ合金膜を厚さ２．２nmで、第２の強磁性膜１５５としてＣｏ₉₀Ｆｅ₁₀合金膜を厚さ８nmで、反強磁性膜１５６としてＦｅ−Ｍｎ合金膜を厚さ８nmで、保護膜１５７としてＴｉ膜を厚さ５nmで順次成膜し、スピンバルブ構造の積層膜を作製した。以上の薄膜は、いずれもイオンビームスパッタリングにて形成した。さらに、この積層膜上にＣｕ電極１５８ａ，１５８ｂを形成することによって、スピンバルブ型磁気抵抗効果素子１５９を得た。
【０１５０】
なお、強磁性膜１５３，１５５におけるＣｏＦｅ系合金膜の組成物としては、大きな抵抗変化率（日本応用磁気学会誌：１６．３１３（１９９２））および軟磁気特性の観点からＣｏ₉₀Ｆｅ₁₀とした。
【０１５１】
このようにして得たスピンバルブ型磁気抵抗効果素子の結晶性、磁気特性および抵抗変化率を測定したところ、ＣｏＦｅ合金膜のＸ線回折による半値幅は１°であり、軟磁気特性を示す物性の一つである保磁力は０．１Ｏｅであった。また、この素子を用いて測定した磁気抵抗変化率は、約１０％という高い値を示した。
【０１５２】
また、比較のため、同じ処理を施した基板を真空装置内に載置し、１×１０^-7Torr以下まで排気した後、通常のＡｒガスを２×１０^-3Torrまで導入し、その基板表面に非晶質Ｓｉ膜を成膜することなく、Ｃｕ膜を下地膜として直接成膜し、その表面に実施例８と同一構成のスピンバルブ構造の積層膜を作製した。さらに、この積層膜上にＣｕ電極を形成して、磁気抵抗効果素子とした。この積層膜は、通常の１３．５６MHz にて励起された２極スパッタリング法によって形成した。
【０１５３】
この磁気抵抗効果素子の結晶性、磁気特性および抵抗変化率を測定したところ、ＣｏＦｅ合金膜のＸ線回折による半値幅は７°であり、軟磁気特性を示す物性の一つである保磁力は１．５Ｏｅであった。また、この素子を用いて測定した磁気抵抗変化率は約５％であった。
【０１５４】
（実施例９）
表面粗さがＲ_a ＝２nm以下のサファイヤ基板を表面清浄化した後、この基板を真空装置内に載置し、１×１０^-9Torr以下まで排気した。真空装置内の水および酸素は、質量分析器および露点計によって管理した。以上の手順が終了した後、電子ビーム蒸着源を用いた超高真空蒸着法によって、第１の下地膜として、非晶質ＣｕＴｉ膜を膜厚３nmで成膜した。その後、真空を保ったまま連続して、励起周波数１００MHz の超高真空ＲＦスパッタリングを用いて、第２の下地膜としてＦｅＭｎ合金膜を膜厚２nmで成膜した。
【０１５５】
次に、上記下地膜上に、Ｔｉ５nm／ＦｅＭｎ８nm／（Ｃｏ₈₁Ｆｅ₉ ）Ｐｄ₁₀８nm／Ｃｕ２．２nm／（Ｃｏ₈₁Ｆｅ₉ ）Ｐｄ₁₀８nmの構成を有するスピンバルブ構造の積層膜を全て励起周波数１００MHz の超高真空ＲＦスパッタリングを用いて形成し、さらにこの積層膜上にＣｕ電極を形成して、スピンバルブ型磁気抵抗効果素子を作製した。
【０１５６】
このようにして得たスピンバルブ型磁気抵抗効果素子の結晶性、磁気特性および抵抗変化率を実施例８と同様に測定したところ、ＣｏＦｅ膜のＸ線回折による半値幅は１．５°であり、軟磁気特性を示す物性の一つである保磁力は１Ｏｅであった。また、同素子を用いて測定した磁気抵抗変化率は、約１２％という高い値を示した。
【０１５７】
（実施例１０）
図１６に示すように、支持基板３０上にＣｏＺｒＮｂ等からなる高抵抗非晶質層３１を形成し、その上にＣｏＦｅ合金等からなる強磁性膜３２、Ｃｕ等よりなる非磁性膜３３、強磁性膜３２、およびＦｅＭｎ等からなる交換バイアス層３４を約４ｋＡ／ｍの静磁界中で順次形成し、交換バイアス層３４上にリード３５を形成して磁気抵抗効果素子を作製した。なお、各層は４元スパッタ装置で下記表４に示す成膜条件で成膜した。
【０１５８】
【表４】

【０１５９】
この磁気抵抗効果素子の磁気特性を調べ、図１７および図１８にそのＭ−Ｈカーブ（磁化−磁界カーブ）を示す。なお、図１７は容易軸方向のＭ−Ｈカーブ、図１８は困難軸方向のＭ−Ｈカーブを示す。
【０１６０】
図１７から分かるように、ＦｅＭｎに固着されていない側のＣｏＦｅ膜の保磁力Ｈｃ（図中ａ）は約５００Ａ／ｍとなり、通常のＣｏＦｅ単層膜のＨｃ約１６００Ａ／ｍに比べ著しく低い値を示した。さらに信号磁界入力側である困難軸方向についても、図１８から分かるように、ＦｅＭｎに固着されていない側のＣｏＦｅ膜の保磁力Ｈｃ（図中ｂ）が約６００Ａ／ｍとなり、通常のＣｏＦｅ単層膜のＨｃ約１６００Ａ／ｍに比べ著しく低い値を示した。
【０１６１】
また、この磁気抵抗効果素子の抵抗変化特性を調べ、図１９にそのＲ−Ｈカーブ（抵抗−磁界カーブ）を示す。図１９から分かるように、抵抗変化率△Ｒ／Ｒは従来のＣｏ系スピンバルブ膜と同程度の約９％の高い抵抗変化率となった。また、ＦｅＭｎに固着されていない側のＣｏＦｅ膜の保磁力Ｈｃ（図中ｃ）は図１７から予想されるように約５００Ａ／ｍの低い値となった。
【０１６２】
本実施例では、交換バイアス層としてＦｅＭｎ膜を用いているが、ＮｉＯ等の反強磁性膜を用いてもよいし、また（Ｃｏ／Ｃｕ）ｎ等の構造を有する人工格子膜を用いても良好な特性が得られることが確認された。さらに、本実施例では、高抵抗アモルファス層としてＣｏＺｒＮｂ膜を用いているが、その他に微小な結晶のＦｅＺｒ膜、ＦｅＺｒＮ膜、ＣｏＺｒＮ膜、ＦｅＴａＣ膜、あるいはＮｉＦｅＸ膜（Ｘ：Ｒｈ，Ｎｂ，Ｚｒ，Ｈｆ，Ｔａ，Ｒｅ，Ｉｒ，Ｐｄ，Ｐｔ，Ｃｕ，Ｍｏ，Ｍｎ，Ｗ，Ｔｉ，Ｃｒ，Ａｕ，またはＡｇ）等を用いてもよい。特に、ｆｃｃ相の微結晶膜（Ｃｏ系窒化膜、Ｃｏ系炭化膜、ＮｉＦｅＸ膜）では、ｆｃｃ相（１１１）配向を促進する効果も相乗し、さらにＨｃが容易軸方向で〜２５０Ａ／ｍに低下し、抵抗変化率が１０％に向上した。
【０１６３】
比較のために、高抵抗アモルファス層を設けないで支持基板上に後述する図２３と同様な強磁性膜、中間層、強磁性膜、交換バイアス層を順次積層してなる磁気抵抗効果素子の磁気特性を調べ、そのＭ−Ｈカーブを図２０および図２１に示す。なお、図２０は容易軸方向のＭ−Ｈカーブ、図２１は困難軸方向のＭ−Ｈカーブを示す。また、成膜条件は前記表３と同様とした。
【０１６４】
図２０から分かるように、ＦｅＭｎに固着されていない側のＣｏＦｅ膜の保磁力Ｈｃ（図中ｄ）は約２０００Ａ／ｍとなり、通常のＣｏＦｅ単層膜のＨｃと同様に高い値を示した。さらに、困難軸方向についても、図２１に示すように、ＦｅＭｎに固着されていない側のＣｏＦｅ膜の保磁力Ｈｃ（図中ｅ）は約１４００Ａ／ｍとなり、通常のＣｏＦｅ単層膜のＨｃと同様に高い値を示し、磁気抵抗効果素子としては不充分であった。
【０１６５】
（実施例１１）
図２２に示すように、支持基板３０上にＣｕ等からなる厚さ約５nmの下地膜３６を形成し、さらにその上に交換バイアス層３４、強磁性膜３２、非磁性膜３３、強磁性膜３２、および高抵抗アモルファス層３１を順次形成し、高抵抗アモルファス層３１上にリード３５を形成して磁気抵抗効果素子を作製した。なお、成膜条件は上記表３と同様にした。
【０１６６】
図２２に示す構造、すなわち高抵抗アモルファス層を交換バイアス層よりも上層として形成する場合においても、低いＨｃを得ることができた。また、アモルファス層が高抵抗であるため、この層が最上層となってもシャント効果による磁気抵抗変化率の低下はなかった。なお、この場合には、ＦｅＭｎの結晶配向制御のために下地膜を設けることが望ましい。
【０１６７】
（実施例１２）
支持基板４１上にＣｏＰｔＣｒ膜４２を厚さ８nmで成膜し、その上にレジスト４３を塗布した後、所望のパターンにレジスト４３をパターニングし、図２３（Ａ）に示すように、イオンミーリング等によりエッチングした。この際、ＣｏＰｔＣｒのテーパ角Ｘは９０°に近い方が望ましい。
【０１６８】
次に、図２５（Ｂ）に示すように、エッチング後のレジスト４３は除去せず、この状態でＣｏＦｅ合金からなる強磁性膜４４、Ｃｕ等からなる非磁性膜４５、強磁性膜４４、および高抵抗アモルファス層４６を順次形成してスピンバルブ構造の磁気抵抗効果素子を作製した。この際、レジスト４３のテーパ角Ｙは９０°に近い方が望ましい。
【０１６９】
次に、レジスト４３を除去した後に高抵抗アモルファス層４６上にリード４７を形成した。なお、このリード４７は、レジスト４３を除去する前に形成してもよい。このように作製することにより、図２５（Ｃ）に示すように、界面状態に敏感なスピンバルブ構造を特性劣化を伴わずに作製することできる。
【０１７０】
上記構造のように、ＦｅＭｎ等からなる交換バイアス層を磁化固着膜として用いることなく、高保磁力膜を用いることができる。高保磁力膜の材料としては、下地膜を用いなくても適当な面内磁気異方性を発揮できる材料を用いることが望ましい。そこで、本実施例では、この特性を満足するＣｏＰｔＣｒ膜を高保磁力膜として用いた。
【０１７１】
（実施例１３）
図２４に示すように、支持基板３０上に高抵抗アモルファス層３１、強磁性膜３２、非磁性膜３３、強磁性膜３２、および高抵抗アモルファス層３１を順次積層し、最上層の高抵抗アモルファス層３１上にリード３５を形成して磁気抵抗効果素子を作製した。
【０１７２】
図２４に示す構造のように、磁化固着膜であるＦｅＭｎからなる交換バイアス層を用いず、センス電流により発生する磁界または形状による反磁界の効果による自己バイアス効果を利用して、強磁性膜３２間での反強磁性的磁化配列を実現してもよい。
【０１７３】
この場合、センス電流により発生する磁界が膜幅方向（図中ｇ方向）において、強磁性膜３２を挟んで上下で反対方向となるように加わるようにし、さらに、膜幅方向の反磁界を低減するために２つの強磁性膜３２は互いに反強磁性的に結合するようにする。その結果、交換バイアス層がなくても２つの強磁性膜３２同士が反強磁性的に結合できる。したがって、信号磁界Ｈｓを膜長手方向（図中ｆ方向）に加えると２つの強磁性膜３２の磁化は回転して膜長手方向に揃い強磁性的な結合となる。その結果、スピン依存散乱に起因した大きな△Ｒ／Ｒを得ることができる。
【０１７４】
（実施例１４）
図２５に示すように、熱酸化Ｓｉ基板１６０上に、高抵抗強磁性膜１６１としてＣｏＣｒ合金膜をイオンビームスパッタ法によって膜厚１nmで成膜した。次に、高抵抗磁性膜１６１上に、第１の強磁性膜１６２としてＣｏＦｅ合金膜を厚さ３nmで、非磁性膜１６３としてＣｕ膜を厚さ２nmで、第２の強磁性膜１６４としてＣｏＦｅ合金膜を厚さ３nmで順次成膜し、スピンバルブ型の積層膜を形成した。
【０１７５】
この後、上記積層膜上に、反強磁性膜１６５としてＦｅＭｎ膜を厚さ１５nmで形成した。その上に、必要に応じて保護膜１６６を形成し、さらに電極１６７ａ，１６７ｂ（間隔：１０μｍ）を形成することによって、スピンバルブ型磁気抵抗効果素子１６８を作製した。
【０１７６】
このようにして得たスピンバルブ型磁気抵抗効果素子の抵抗変化率を測定したところ、室温で１４％という高い値を示した。
【０１７７】
比較として、高抵抗強磁性膜１６１を形成しない以外は実施例１４と同様にして、スピンバルブ型磁気抵抗効果素子を作製した。このスピンバルブ型磁気抵抗効果素子の特性を実施例１４と同様にして評価したところ、室温での抵抗変化率は１２％であった。
【０１７８】
（実施例１６）
サファイア基板上に、第１の強磁性膜としてＣｏ₉₀Ｆｅ₁₀合金膜、非磁性膜としてＣｕ膜、第２の強磁性膜としてＣｏ₉₀Ｆｅ₁₀合金膜、反強磁性膜としてＦｅＭｎ膜を順に形成した。この際、第１および第２の強磁性膜の厚さ（ｄ_FeCo）を変化させて、抵抗変化率（Δρ／ρ₀ ）を測定した。その結果を図２６に示す。なお、第１および第２の強磁性膜の厚さは同一とし、Ｃｕ膜の膜厚は２．２nm、ＦｅＭｎ膜の膜厚は１５nmとした。また、上記磁気抵抗効果素子においては、反強磁性膜上に必要に応じて、耐食性等に優れたＴａ、Ｎｉ、ＮｉＣｒ等の保護膜を介して電極を形成する。図２６から分かるように、ｄ_FeCoが５nm以下でＭＲ効果が増大していることが分かる。また、ｄ_FeCo＝３nm付近でピークをとり、２〜４nmが好ましい範囲となる。
【０１７９】
強磁性膜／非磁性膜（金属薄膜）／強磁性膜のサンドイッチ構造の厚さが薄くなってくると、金属薄膜と接していない面での電子散乱が大きくなり、抵抗のサイズ効果が表れる。サンドイッチ構造の比抵抗の変動分（Δρ）は、サンドイッチ構造のトータルの膜厚をｔ、平均自由行程をｌ₀ とすると、Δρはｌ₀ ／ｔに比例する。諸条件で変化するが、図２６からも明らかなように、Ｃｏ系強磁性膜を用いた場合、強磁性膜厚は５nm以下とすることが良好なＭＲ効果が得る上で好ましい。
【０１８０】
すなわち、強磁性膜の金属薄膜と接していない方の面に、低抵抗例えば３０μΩcm以下の比抵抗をもった材料が接している場合、電子はその界面を通り抜け、３０μΩcm以下の比抵抗をもった材料の中に流れてしまい、有効な表面散乱が起こりにくくなる。このため、有効な表面散乱を引き起こし、サイズ効果を利用するためには、３０μΩcm以上の材料とするか、接している材料の膜厚を５nm以下とすることが有効である。
【０１８１】
サイズ効果を利用し、大きなＭＲ効果を得るためには、Ｃｏ系強磁性膜の膜厚は５nm以下にすることが好ましい。このとき、中間金属薄膜としては、Ｃｕ、Ａｇ、Ａｕ等の比抵抗の小さい金属を用いることが望ましく、中間金属薄膜の膜厚はサイズ効果を利用するために、５nmより薄いことが好ましい。また、両強磁性膜の膜厚が大きく異なっている場合には、両強磁性膜における表面散乱の効果が異なってしまうため、磁気抵抗変化率は小さくなってしまう。このため、両強磁性膜の厚さの比は、１：１〜１：２の間にあることが望ましい。
【０１８２】
（実施例１６）
図２７に示すように、サファイア基板１６０上に非磁性膜１６１としてＣｕＰｄ合金膜をＲＦスパッタ法によって厚さ２nmで成膜した。次に、非磁性膜１６１上に、第１の強磁性膜１６２としてＣｏＦｅ合金膜を厚さ１nmで、非磁性膜１６３としてＣｕ膜を厚さ２nmで、第２の強磁性膜１６４としてＣｏＦｅ合金膜を厚さ３nmで順次成膜し、スピンバルブ型の積層膜を形成した。
【０１８３】
この後、上記積層膜上に、反強磁性膜１６５としてＦｅＭｎ膜を厚さ１５nmで形成した。その上に、必要に応じて保護膜１６６を形成し、さらに電極１６７ａ，１６７ｂを形成することによって、スピンバルブ型磁気抵抗効果素子１７１を作製した。
【０１８４】
この磁気抵抗効果素子では、反強磁性膜１６５により、第２の強磁性膜１６４には一方向異方性が与えられているため、低磁場中では磁化は一方向に固定されたまま動かない。これに対して、第１の強磁性膜１６２は、低磁場中でも磁場の方向に磁化を向ける。よって、外部磁化を変化させることにより、２つの強磁性膜の磁化の成す角度を自由に制御することができる。なお、反強磁性膜１６５は、第２の強磁性膜１６４に有効な一方向異方性を与える上で、１〜５０nm程度の厚さとすることが好ましい。
【０１８５】
このようにして得たスピンバルブ型磁気抵抗効果素子１７１の抵抗変化率を測定したところ、第１の強磁性膜１６２の厚さを１nmと薄くしているにもかかわらず、室温で８％という高い値を示した。また、上記スピンバルブ型磁気抵抗効果素子１７１を、幅２μｍ×長さ８０μｍの微細形状に加工してＣｕリード間を２μｍに規定した狭トラック幅の高密度磁気記録の再生に用いたところ、バルクハウゼンノイズを除去することができた。
【０１８６】
比較として、非磁性膜１６１を形成しない以外は実施例１７と同様にして、スピンバルブ型磁気抵抗効果素子を作製した。このスピンバルブ型磁気抵抗効果素子の特性を実施例１７と同様にして評価したところ、抵抗変化率は室温で３％と小さい値しか得られなかった。
【０１８７】
また、第１の強磁性膜１６２の膜厚を６nmとする以外は実施例１６と同様にして、スピンバルブ型磁気抵抗効果素子を作製した。このスピンバルブ型磁気抵抗効果素子の特性を実施例１６と同様にして評価したところ、抵抗変化率は室温で６％得ることができたが、実施例１６と同様な再生微細素子により高密度記録（狭トラック幅）の再生を行ったところ、反磁界によるバルクハウゼンノイズが観測された。
【０１８８】
（実施例１７）
図２８に示すように、熱酸化Ｓｉ基板１６０上に平均自由行程が長い薄膜１７２として、キャリア濃度が１０²⁰cm^-3となるようにＴｅをドープしたＧａＡｓ膜をＭＢＥ法により厚さ１０nmで成膜した。次に、ＴｅドープＧａＡｓ膜１７２上に第１の強磁性膜１６２としてＣｏＦｅ合金膜を厚さ１nmで、非磁性膜１６３としてＣｕ膜を厚さ２nmで、第２の強磁性膜１６４としてＣｏＦｅ合金膜を厚さ４nmで順次成膜し、スピンバルブ型の積層膜を形成した。
【０１８９】
この後、上記積層膜上に、反強磁性膜１６５としてＦｅＭｎ膜を厚さ１５nmで形成した。その上に、必要に応じて保護膜１６６を形成し、さらに電極１６７ａ，１６７ｂを形成することによって、スピンバルブ型磁気抵抗効果素子１７３を作製した。
【０１９０】
このようにして得たスピンバルブ型磁気抵抗効果素子の抵抗変化率を測定したところ、室温で１８％という高い値を示した。また、上記スピンバルブ型磁気抵抗効果素子を高密度磁気記録の再生に用いて、１０⁵ Ａ／cm² という電流密度のセンス電流における出力信号電圧を測定したところ、１ｍＶ_p-p という良好な値が得られた。
【０１９１】
比較として、ＴｅドープＧａＡｓ膜１７２を形成しない以外は、実施例１７と同様にして、スピンバルブ型磁気抵抗効果素子を作製した。このスピンバルブ型磁気抵抗効果素子の特性を実施例１７と同様にして評価したところ、抵抗変化率は室温で２％と小さい値しか得られなかった。
【０１９２】
（実施例１８）
ガラス基板上に厚さ１０nmのＣｕ膜を下地膜として形成し、その上にＣｏ₉₀Ｆｅ₁₀膜を形成した。Ｃｕ膜およびＣｏ₉₀Ｆｅ₁₀膜は、ＲＦ２極スパッタリング法により成膜した。なお、スパッタリングは、成膜中に永久磁石により約４０００Ａ／ｍの一方向磁界を基板近傍に加え、以下に示すスパッタリング条件により行った。
【０１９３】

このようにして作製したＣｏ₉₀Ｆｅ₁₀膜のＨｃ（困難軸方向）とＣｏ₉₀Ｆｅ₁₀膜の膜厚の関係を図２９に示す。また、図２９には、比較のためガラス基板上にＣｕ下地膜を設けないで直接Ｃｏ₉₀Ｆｅ₁₀膜を形成したものも示した。なお、保磁力Ｈｃは振動型磁力計により測定した。
【０１９４】
図２９から分かるように、Ｃｕ下地膜を設けない通常のＣｏ₉₀Ｆｅ₁₀膜では、膜厚２０nm以下では２０００Ａ／ｍ以上の高いＨｃを示した。一方、Ｃｕ下地膜を設けると、膜厚２０nmのＣｏ₉₀Ｆｅ₁₀膜ではＨｃの低下は僅かであったが、膜厚１０nm以下では４００〜９００Ａ／ｍにＨｃが大幅に低下した。このように、ガラス基板とＣｏ₉₀Ｆｅ₁₀膜との間にＣｕ下地膜を設けることにより、Ｃｏ₉₀Ｆｅ₁₀膜のＨｃを低減できることが分かった。特に、Ｃｕ下地膜の膜厚は、１原子層以上であれば上記のＨｃ低減の効果が認められた。なお、Ｃｕ下地膜上にまったく同様にＣｏ膜を形成した場合はＣｏＦｅ膜の場合ほどＨｃの低下は認められなかった。
【０１９５】
（実施例１９）
ガラス基板上に厚さ５〜６nmのＣｕ下地膜を形成し、さらにＣｕ下地膜上にＣｏ₉₀Ｆｅ₁₀膜、厚さ２nmのＣｕ中間層、およびＣｏ₉₀Ｆｅ₁₀膜を順次形成した。なお、これらの膜の成膜条件は実施例１８と同様とした。
【０１９６】
この積層膜（Ｃｕ／ＣｏＦｅ／Ｃｕ／ＣｏＦｅ）におけるＨｃ（困難軸方向）とＣｏ₉₀Ｆｅ₁₀膜の膜厚の関係を図３０を示す。また、図３０には、図２９と同様にガラス基板上にＣｕ下地膜を設けないで直接Ｃｏ₉₀Ｆｅ₁₀膜を形成したものも示した。
【０１９７】
図３０から分かるように、Ｃｕ下地膜を設けない積層膜では、単位Ｃｏ₉₀Ｆｅ₁₀膜の膜厚が５nm以上でＨｃは急激に増加するが膜厚３nm以下でＨｃが８００Ａ／ｍである。このように、単にＣｕ中間層を設けるだけでもＨｃを低減できる。さらに、この積層膜にＣｕ下地膜を設けることによりＨｃはさらに低下でき、単位Ｃｏ₉₀Ｆｅ₁₀膜の膜厚が７nm以下で２２０〜４００Ａ／ｍの低いＨｃが得られることが分かる。したがって、Ｃｕ下地膜とＣｕ中間層を用いたＣｏ₉₀Ｆｅ₁₀積層膜では、実施例１８の場合よりもＨｃを大幅に低減できる。
【０１９８】
また、Ｃｕ５nm／Ｃｏ₉₀Ｆｅ₁₀２．２nm／Ｃｕ２nm／Ｃｏ₉₀Ｆｅ₁₀２．２nmの積層膜の磁化曲線（容易軸方向）を図３１に示す。図３１から分かるように、磁界が０でも残留磁化が９０％以上であり、この２つのＣｏ₉₀Ｆｅ₁₀強磁性膜の磁化は反強磁性的ではなく強磁性的な磁化挙動を示すことが分かる。
【０１９９】
（実施例２０）
Ｃｏ₉₀Ｆｅ₁₀膜の単位膜厚を１．５nmとし、Ｃｕ膜の単位膜厚を１．５nmとして、（ＣｏＦｅ／Ｃｕ）ｎ膜を実施例１８に示す成膜条件で作製し、そのＨｃと積層回数ｎとの関係を調べた。その結果を図３２に示す。この場合、ガラス基板上にＣｏ₉₀Ｆｅ₁₀膜、Ｃｕ膜の順に積層したものと、Ｃｕ膜、Ｃｏ₉₀Ｆｅ₁₀膜の順に積層したもの（第１層のＣｕは下地膜に相当すると見なされる）について調べた。
【０２００】
図３２から分かるように、積層回数が２の場合において、Ｃｏ₉₀Ｆｅ₁₀膜を先に形成したときは、Ｈｃは６５０Ａ／ｍと若干高いが、積層回数が４〜８の場合においては、Ｃｏ₉₀Ｆｅ₁₀膜が先でもＣｕ膜が先でもＨｃは１００〜３００Ａ／ｍと低い。これは、積層回数が増えるにしたがってＣｕ下地膜の効果が薄らぎ、Ｃｕ下地膜（第１層のＣｕ膜）の有無に拘らずＨｃが低くなるからであると考えられる。なお、この場合の磁化曲線も、図３１と同様に強磁性的な結合を示す形状であった。
【０２０１】
なお、この積層膜は、断面透過電子顕微鏡観察やＸ線回折曲線の回折ピーク半値幅の測定から、結晶粒径が大きい、すなわちＣｕ膜とＣｏ₉₀Ｆｅ₁₀膜との界面で連続したエピタキシ的に結晶が成長していることが分かった。したがって、この積層膜は、非磁性膜と強磁性膜との界面での結晶成長遮断効果を利用した微結晶効果により軟磁性を発揮せしめている従来のＦｅ／Ｃ等の多層膜とは異なり、余分な抵抗増大がないので、スピン依存散乱を利用した磁気抵抗効果膜への応用が可能である。
【０２０２】
（実施例２１）
（Ｃｏ₉₀Ｆｅ₁₀／Ｃｕ）ｎ膜では、Ｃｕ膜厚に応じてＣｕ膜に隣接する強磁性膜の磁化が反強磁性的に結合したり、強磁性的に結合したりすることが知られている。図３３に（Ｃｏ₉₀Ｆｅ₁₀（１nm）／Ｃｕ）₁₆における困難軸方向のＨｓ（飽和磁界）と単位Ｃｕ膜の膜厚との関係を示す。Ｃｕ膜の膜厚を１nm、２nm近傍に設定すると、隣接する強磁性膜間の反強磁性結合に起因する大きなＨｓ（１２〜２４０ｋＡ／ｍ）を示す。また、容易軸方向でも図３４に示すような残留磁化が大幅に低下した反強磁性的結合を表わす磁化曲線を示す。一方、それ以外の膜厚では、図３１に示した磁化曲線と同様にＣｏ₉₀Ｆｅ₁₀の誘導磁気異方性に相当する程度のＨｓ（１０００〜２０００Ａ／ｍ）を示し、また、容易軸方向の磁化曲線も残留磁化が９０％以上であり、反強磁性結合がない特性を示した。
【０２０３】
また、図３３から分かるように、膜厚を例えば１．５nm程度の中間値に設定することにより強磁性的結合が得られることが分かる。強磁性的結合であれば、Ｈｓが低いために磁気ヘッド等の磁気センサ応用上重要である困難軸方向の透磁率を高くできる。このように、本実施例においてＣｕ膜の膜厚は、従来の巨大磁気抵抗効果を示す人工格子膜とは異なり、反強磁性結合しない中間値であることが望ましい。
【０２０４】
（実施例２２）
基板５０上に実施例１８と同様の成膜条件で強磁性積層単位５１を形成した。ここで、強磁性積層単位５１は、実施例２０および実施例２１において示した非磁性膜であるＣｕ膜と強磁性膜であるＣｏ₉₀Ｆｅ₁₀膜との積層膜をいう。次いで、強磁性積層単位５１上に、強磁性積層単位中の非磁性膜と異なる厚みを有する非磁性膜５２を形成し、さらにその上に強磁性積層単位５１を形成した。次いで、その上にＦｅＭｎ、ＮｉＯ、ＮｉＣｏＯ等からなる反強磁性膜５３を形成し、さらにその上に保護膜５４を形成した。この保護膜５４は必要に応じて形成する。最後に、エッジ部に電流を供給するために保護膜５４上に電極端子５５を形成して図３５に示す磁気抵抗効果素子を作製した。
【０２０５】
ここで、強磁性積層単位５１および反強磁性膜５３の成膜を一方向磁界中で行うことにより、反強磁性膜５３と直接接する強磁性積層単位５１に交換バイアスを付与することができる。なお、反強磁性膜５３と交換結合する強磁性積層単位５１中の強磁性膜の磁化は固着されるので、強磁性積層単位５１の代わりに軟磁性が若干低いＣｏＦｅ単層膜を用いてもよい。また、フェロ結合したＣｏＦｅ／Ｃｕ界面は必ずしも平坦である必要はなく、図３６に示すように、Ｃｕ膜内に層状のＣｏＦｅが混在した状態でも同様な効果を発揮する。
【０２０６】
強磁性積層単位５１を（Ｃｏ₉₀Ｆｅ₁₀１nm／Ｃｕ１．２nm）₄ 膜とし、非磁性膜５２を厚さ２．５nmのＣｕ膜とし、反強磁性膜５３を厚さ１０nmのＦｅＭｎ膜とし、保護膜５４を厚さ６nmのＣｕ膜とした磁気抵抗効果素子の磁化曲線および抵抗変化特性（磁界方向は容易軸方向）をそれぞれ図３７および図３８に示す。なお、抵抗は４端子法により測定した。
【０２０７】
図３７および図３８から分かるように、Ｈ＞８００Ａ／ｍで２つの強磁性積層単位５１の間において磁化が反強磁性的に結合しており、Ｈ＜５００Ａ／ｍで２つの強磁性積層単位５１の間において磁化が強磁性的に結合している。すなわち、Ｈ＝５００〜８００Ａ／ｍの間で磁化が強磁性的結合から反強磁性的結合に変化していることが分かる。このＨ＝５００〜８００Ａ／ｍの僅かな磁界領域、すなわち僅かなヒステリシスで抵抗が大きく変化しており、このときの抵抗変化率ΔＲ／Ｒは８％である。
【０２０８】
比較のために、Ｃｏ₉₀Ｆｅ₁₀単層膜からなる図３５に示すスピンバルブ構造の磁気抵抗効果素子（強磁性積層単位５１をＣｏ₉₀Ｆｅ₁₀単層膜に置き換えたもの）の磁化曲線および抵抗変化特性をそれぞれ図３９および図４０に示す。
【０２０９】
図３９および図４０から分かるように、図３８の抵抗変化と比べて磁化曲線にヒステリシスが大きく、その結果、抵抗変化特性にも大きなヒステリシスが存在する。また、ΔＲ／Ｒは約６．５％であり、図３７の抵抗変化よりも小さい値である。
【０２１０】
以上の説明から、本発明の強磁性積層膜を用いたスピンバルブ構造の磁気抵抗効果素子は、軟磁性が良好であり、僅かな磁界で大きな抵抗変化を得られ、さらに強磁性積層単位内部にＣｏ₉₀Ｆｅ₁₀／Ｃｕ界面が存在するので抵抗変化率が大きいことが分かる。
【０２１１】
以上までは（ＣｏＦｅ／Ｃｕ）ｎ積層膜の実施例について詳しく述べたが、このスピンバルブ構造は他の強磁性膜（例えば、ＮｉＦｅ，ＮｉＦｅＣｏ，Ｃｏ等）と他の非磁性膜（Ｃｕ基合金等）との積層においても同様な効果が期待できる。次に、図３５におけるスピンバルブ構造において、強磁性積層単位５１を種々の強磁性結合多層膜に変えた場合の容易軸方向の抵抗変化率とＨｃを下記表５に示す。
【０２１２】
【表５】

【０２１３】
表５から分かるように、ＣｏＦｅ／Ｃｕ以外の組み合わせの強磁性多層膜を用いても単層磁性膜を用いたスピンバルブ膜（表２参照）に比べてＨｃが低減でき、かつ同等以上の抵抗変化率が実現できることが分かる。
【０２１４】
（実施例２３）
図３５における基板側の強磁性積層単位５１として厚さ４nmのＣｕ下地膜と厚さ５nmのＣｏ₉₀Ｆｅ₁₀を用い、反強磁性膜５３側の強磁性積層単位５１に厚さ８nmのＣｏ₉₀Ｆｅ₁₀単層膜を用いた場合の磁化曲線および抵抗変化特性をそれぞれ図４１（Ａ），図４１（Ｂ）および図４２に示す。
【０２１５】
図４１（Ａ）から分かるように、容易軸方向ではＨｃが８００Ａ／ｍ以下と比較的大きい値を示すが、図４１（Ｂ）から分かるように、困難軸方向では１００Ａ／ｍ以下の低い値を示す。また、図４２から分かるように、抵抗変化率ΔＲ／Ｒは容易軸方向で７．２％、困難軸方向で２．８％である。このように困難軸方向で抵抗変化率が低いことは、両強磁性層間でのフェロ結合のために反平行磁化配列が不充分であると考えられ、硬質磁性膜等により反平行磁化配列を促進するバイアス磁界を加えることにより容易軸方向と同程度のΔＲ／Ｒを得ることができる。すなわち、Ｃｕ下地膜とＣｏ₉₀Ｆｅ₁₀膜の積層膜を用いても良好な軟磁性と高いΔＲ／Ｒの両方が得られる。
【０２１６】
（実施例２４）
基板５０上に実施例２２において使用した強磁性膜積層単位５１と、強磁性膜積層単位５１の中の非磁性層と異なる厚みを有する非磁性膜５２とを交互に少なくとも２回以上積層した。さらに、最上層の非磁性膜５２上に保護膜５４を形成した。この保護膜５４は必要に応じて形成する。最後に、エッジ部に電流を供給するための電極端子５５を形成して図４３に示す磁気抵抗効果素子を作製した。
【０２１７】
強磁性積層単位５１を（Ｃｏ₉₀Ｆｅ₁₀１nm／Ｃｕ０．６nm）₄ 膜とし、非磁性層５２を厚さ２．２nmのＣｕ膜とし、積層回数ｎを８としたものの困難軸方向の磁化曲線と抵抗変化特性を図４４および図４５に示す。
【０２１８】
図４４および図４５から分かるように、飽和磁界Ｈｓは６０００Ａ／ｍと比較的小さな値を示し、Ｈｃは２４０Ａ／ｍと小さな値を示す。このとき、抵抗変化率は１２％以下であり、抵抗変化が飽和する磁界は磁化曲線における飽和磁界Ｈｓとほぼ一致し、また、ヒステリシスは磁化曲線のＨｃとほぼ一致する。これにより、僅かな磁界で大きな抵抗変化率を示すことが分かる。
【０２１９】
（実施例２５）
鏡面状態に加工したＭｇＯ基板６０の（１１０）面上に（Ｃｏ₉₀Ｆｅ₁₀１nm／Ｃｕ１．１nm）₁₆積層膜６１を形成した。この積層膜６１をメタルマスクを用いて１×８mm² のストライプ状にパターニングした。次いで、積層膜６１上にエッジ部に電流を供給するための電極端子６２を形成して磁気抵抗効果素子を作製した。なお、積層膜６１上に保護膜として厚さ５．５nmのＣｕ膜を形成してもよい。また、ＣｏＦｅ系合金膜の組成は、大きな抵抗変化率を示すこと［日本応用磁気学会誌、16,313(1992)] および軟磁気特性の点からＣｏ₉₀Ｆｅ₁₀とした。
【０２２０】
この場合、ＭｇＯ基板６０の（１１０）面上にはＣｏ₉₀Ｆｅ₁₀膜から形成した。Ｃｕ膜から形成すると、１０％以上の大きな抵抗変化を得ることができないからである。図４６において、積層膜６１に示されている波形線は主成長面の断面を示している。この主成長面が揺らいでいる方向に、ＭＲセンス電流（Ｉｓ）を流す。
【０２２１】
ここで、積層膜６１を成膜する成膜装置としては、多元同時スパッタリング装置を用いた。このスパッタリング装置は、Ｃｏ₉₀Ｆｅ₁₀ターゲットをＲＦスパッタ、ＣｕターゲットをＤＣスパッタできるような構成になっており、それぞれのターゲット上に交互に直流バイアスを印加した基板を通過させて成膜するものである。なお、主排気ポンプにはクライオポンプを使用した。この成膜装置を用いて、真空チャンバー内を５×１０^-7Torr以下にまで排気した後、真空チャンバー内にＡｒガスを導入し、約３ mTorrとしてスパッタリングを行った。
【０２２２】
得られた磁気抵抗効果素子の抵抗変化率および結晶構造を調べた。なお、抵抗変化率は、静磁界方向の抵抗変化を四端子法で測定した。このときの電流密度は２．０〜２．５ＫＡ／cm² とした。また、結晶構造は、以下の測定条件でＸ線回折法によりθ−２θスキャンおよび主回折面に関するロッキングカーブを測定することにより評価した。
【０２２３】
Ｘ線回折測定条件
（１）θ−２θスキャン
Ｃｕ−Ｋα、４０ｋＶ、２００ｍＡ
スキャン幅：２θ＝２〜１００°
ステップ幅：０．０３°
係数時間 ：０．５秒
（２）ロッキングカーブ
Ｃｕ−Ｋα、４０ｋＶ、２００ｍＡ
スキャン幅：２θ＝２０〜６０°
ステップ幅：０．０４°
係数時間 ：０．５秒
図４７（Ａ）および図４７（Ｂ）に磁気抵抗効果素子の積層膜のθ−２θスキャンによるＸ線回折曲線を示す。図４７（Ｂ）に示すように、２θ＝７５°付近に、ｆｃｃ相（２２０）面反射に相当する強い回折ピークが確認できる。これにより、Ｘ線回折曲線から積層膜の主成長面は一方向に歪みのあるｆｃｃ相（２２０）面であることが分かる。なお、図４７（Ａ）における２θ＝４°付近のピークは、積層周期（〜２．１nm）による回折である。
【０２２４】
次に、この主成長面に関して、［１００］軸方向および［１１０］軸方向からロッキングカーブを測定した。その結果を図４８（Ａ）および図４８（Ｂ）に示す。図４８（Ａ）には、［１１０］軸方向から測定したロッキングカーブを示す。これよりθ＝３８°近傍に一つのピークが確認できる。一方、図４８（Ｂ）には［１００］軸方向からのロッキングカーブを示す。これよりθ＝３３°と４１°付近の２つのピークの存在が確認できる。
【０２２５】
図４９（Ａ）および図４９（Ｂ）に図４８のロッキングカーブから判断される膜構造の概念図を示す。図４９（Ａ）においてうねった層は、主成長面のｆｃｃ相（１１０）面を示す。θ−２θスキャンＸ線回折法で測定される平均的な結晶成長面は（１１０）であるが、この（１１０）面は［１００］軸方向に揺らいでいる。一方、［１１０］軸方向の揺らぎは極めて小さい。これは、図４８（Ｂ）に示すロッキングカーブの２つのピーク（［１００］軸方向測定）と、図４８（Ａ）に示す１つのピーク（［１１０］軸方向測定）に対応する。
【０２２６】
図４９（Ｂ）にこの成長面の法線の膜面内成分分布を示した。この膜面内異方性は、［１００］軸方向の大きな揺らぎにより、［１００］軸方向に大きく、［１１０］軸方向に小さい面内分布となっている。後述するように、［１１０］軸方向にＭＲセンス電流を流した場合の抵抗変化率（△Ｒ／Ｒ）は、約３０％であるのに対して、［１００］軸方向に流した場合は、約３５％を示す。
【０２２７】
次に、この積層膜の磁気特性を測定した。その結果に基づく磁気曲線を図５０（Ａ）および図５０（Ｂ）に示す。図５０（Ａ）は外部磁界Ｈを［１００］軸に平行に印加した場合の磁化曲線を示し、図５０（Ｂ）は外部磁界Ｈを［１１０］軸に平行に印加した場合の磁化曲線を示す。なお、磁気抵抗効果素子の磁気特性は、振動型磁力計（ＶＳＭ）で最大印加磁界１．２ＭＡ／ｍで測定した。また、磁化曲線の磁化量Ｍは飽和磁化Ｍｓを規格化して示した。
【０２２８】
図５０（Ａ）および図５０（Ｂ）から分かるように、［１００］軸が磁化容易軸、［１１０］軸が磁化困難軸である。このとき磁化容易軸の飽和磁界は約２４０ｋＡ／ｍであり、磁化困難軸の飽和磁界は約９６０ｋＡ／ｍである。
【０２２９】
このように、本実施例では、基板上に強磁性膜と非磁性膜とを順次少なくとも１回ずつ積層した積層膜を具備し、センス電流の方向が前記積層膜の結晶配向面の揺らぎ方向に沿う方向に設定されていることを特徴とする磁気抵抗効果素子を提供する。
【０２３０】
本実施例において、積層膜の主結晶配向面の法線は、結晶配向面の揺らぎにより膜面内で成分を持ち、その膜面内成分は異方性を有する。あるいは、結晶性の積層膜に発生する面欠陥の法線は、膜面内への揺らぎを持ち、この揺らぎは膜面内で異方性を有する。その異方性が強い方向は、膜成長する原子面において強磁性原子と非磁性原子が混在しやすい方向である。
【０２３１】
その方向に、すなわち膜面内成分による異方性が最も大きくなる方向にセンス電流を流すことにより、電子がスピン依存散乱する確率が高くなる。その結果、磁気抵抗効果素子は、より高い抵抗変化率を示す。
【０２３２】
（実施例２６）
基板に印加するバイアスを変化させて、実施例２５と同じ積層膜構造を有する種々の磁気抵抗効果素子を作製した。図５１に抵抗変化率のバイアス電圧依存性を示す。なお、ＭｇＯ基板の（１１０）面においてそれぞれ直交する［１００］軸と［１１０］軸に平行に電流を流して測定した。図５１から分かるように、それぞれの軸とも、抵抗変化率のバイアス依存性が弱く、［１００］軸で約３５％、［１１０］軸で約３０％の値を示す。すなわち、［１００］軸のほうが［１１０］軸よりも抵抗変化率が大きいことが分かる。
【０２３３】
（実施例２７）
積層膜を（Ｃｕ２nm／Ｃｏ₉₀Ｆｅ₁₀１nm）₁₆膜とすること以外は実施例２５と同様にして磁気抵抗効果素子を作製した。
【０２３４】
このようにＣｕ膜の膜厚を２nmに増加させた場合、［１００］軸方向に電流を流した時の抵抗変化率は約２５％であり、［１１０］軸方向では約１９％であった。したがって、Ｃｕ膜の膜厚を増加させても、この抵抗変化率の方向依存性は保たれていることが分かる。この場合も、主成長面（ｆｃｃ相（２２０）面）のロッキングカーブには、図４８（Ｂ）に示すように［１００］軸で２つのピーク、図４８（Ａ）に示すように［１１０］軸で１つのピークが確認された。
【０２３５】
なお、同様の構成でＣｕ膜の膜厚およびＣｏ₉₀Ｆｅ₁₀膜の膜厚をそれぞれ０．３nmから１０nmまで変化させても、ロッキングカーブの傾向は上記と変わらず、［１００］軸の方が揺らぎが大きい。また、抵抗変化率も［１００］軸のほうが大きい傾向を示した。
【０２３６】
また、同様の構成で積層回数を２から７０まで変化させても、ロッキングカーブおよび抵抗変化率の傾向は変わらず、［１００］軸方向にセンス電流を流すほうが大きな抵抗変化が得られた。
【０２３７】
（実施例２８）
積層膜を（Ｒｕ１nm／Ｃｏ₉₀Ｆｅ₁₀１nm）₁₆膜とすること以外は実施例２６と同様にして磁気抵抗効果素子を作製した。
【０２３８】
この磁気抵抗効果素子の△Ｒ／Ｒは、［１００］軸方向にセンス電流を流す場合の方が［１１０］軸方向にセンス電流を流す場合より大きかった。また、Ｒｕ膜の膜厚を変化させても前記の傾向が認められた。
【０２３９】
この現象は、Ｃｏ₉₀Ｆｅ₁₀膜の代わりにＣｏ膜を用いた場合でも確認できた。また、Ｒｕ以外にＡｇ、Ａｕ、Ｐｄ、Ｐｔ、Ｉｒを積層膜の材料に使用してもＭｇＯ基板の（１１０）面上における軸方向による△Ｒ／Ｒの差が確認できた。
【０２４０】
（実施例２９）
積層膜を（Ｃｕ１．１nm／Ｎｉ₈₀Ｆｅ₂₀１．５nm）₁₆膜とすること以外は実施例２５と同様にして磁気抵抗効果素子を作製した。
【０２４１】
この磁気抵抗効果素子の積層膜の［１００］軸方向にセンス電流を流した場合、その抵抗変化率は２１％であった。一方、［１１０］軸方向にセンス電流を流した場合の抵抗変化率は１７％であった。また、この積層膜もＣｏ₉₀Ｆｅ₁₀／Ｃｕ積層膜の場合同様に、結晶成長面はｆｃｃ相（１１０）面であり、ロッキングカーブ測定から成長面は［１００］軸方向に揺らいでいることが分かった。なお、Ｎｉ₈₀Ｆｅ₂₀膜の膜厚およびＣｕ膜の膜厚を０．５nm〜５０nmと変化させても同様の傾向を示した。
【０２４２】
また、強磁性膜の材料としてＣｏ、ＣｏＦｅ合金、ＮｉＦｅ合金、Ｆｅ、ＦｅＣｒ合金等を用いても、非磁性膜の材料としてＣｕ、Ａｕ、Ａｇ、Ｃｒ、Ｒｕ、ＣｉＮｉ合金等を用いても、積層膜の主成長面が揺らいでいる結晶軸方向とセンス電流方向が平行であれば大きな抵抗変化率を示すことが分かった。
【０２４３】
（実施例３０）
ＧａＡｓ基板の（１１０）面上に厚さ１．５nmのＣｏ膜、厚さ５０nmのＧｅ膜、および厚さ１．５nmのＡｕ膜を形成した。さらに、その上にＭＢＥ法を用いて図５３に示す（Ｃｕ０．９nm／Ｃｏ₉₀Ｆｅ₁₀１nm）₂₀積層膜を形成した。図中６９はＣｕ膜を示し、７１はＣｏ₉₀Ｆｅ₁₀膜を示す。さらに、積層膜上に保護膜として厚さ５nmのＧｅ膜を形成して磁気抵抗効果素子を作製した。この積層膜はｆｃｃ相（１１１）面成長を示していた。このとき、センス電流の方向に関係なく、抵抗変化率は約１５％を示した。
【０２４４】
次に、Ａｕ下地膜の厚さ０．８nmとし、それ以外の構造を上記と同様にして磁気抵抗効果素子を作製した。
【０２４５】
得られた２つの磁気抵抗効果素子を透過電子顕微鏡で観察したところ、Ａｕ下地膜の厚さが１．５nmのものは、ほぼ格子欠陥がなく、極めて良好な結晶性を有するものであった。一方、Ａｕ下地膜の厚さが０．８nmのものは、｛１１１｝面配向を示していたが、｛１００｝面が＜１１０＞軸方向に滑ったことにより積層欠陥が観察された。また、この磁気抵抗効果素子における＜２１１＞軸および＜１１０＞軸方向の抵抗変化率を測定したところ、＜１１０＞軸方向では約１５％であり、＜２１１＞方向では１７％と増加していた。この結果、方向性を持った欠陥が入ることにより、抵抗変化率のセンス電流の方向依存性が発生することが分かる。
【０２４６】
図５３に図５２における積層膜の原子配列図を示す。｛１００｝原子面が＜１１０＞方向にずれることによって、電流が＜２１１＞方向に流れる場合と、＜１１０＞方向に流れる場合で、単位長当り遭遇する界面の数が異なり、＜２１１＞方向で多いことが分かる。このような方向性を持つ格子欠陥による生じる伝導電子のスピン依存界面散乱サイト数の結晶軸方向依存性は、上述した積層欠陥の他に双晶欠陥でも発生したことが分かった。以下に、その例について説明する。
【０２４７】
ＧａＡｓ基板の（１００）面上に厚さ３nmのＡｕ下地膜を形成し、さらにその上に（Ｃｏ₉₀Ｆｅ₁₀１nm／Ｃｕ１．１nm）₁₆積層膜を形成した。この積層膜はｆｃｃ相（１００）面配向を示した。このとき、＜１１１＞軸を中心軸として双晶が発生した。積層膜断面を＜１１０＞方向から観察した場合の原子配列を図５５に示す。図５４から分かるように、＜１１１＞軸まわりに双晶が発生することにより、＜１１０＞方向にＣｕと、ＣｏもしくはＦｅ原子との界面が現れることが分かる。
【０２４８】
この積層膜の抵抗変化率のセンス電流方向依存性を＜１１０＞軸および＜１００＞軸方向において測定した。図５５に｛１００｝面成長した積層膜の双晶面および電流方向と抵抗変化率との相関を示す。図５５から分かるように、抵抗変化率はセンス電流を＜１１０＞軸方向に流したときは１８％を示し、＜１００＞軸方向にセンス電流を流したときは１６％の値を示す。このように｛１１１｝面と大きな角度で交わる＜１１０＞軸の抵抗変化率が高く現れた。一方、双晶が発生しなかったときは、抵抗変化率のセンス電流方向依存性は確認できなかった。
【０２４９】
（実施例３１）
ガラス基板上に（Ｃｕ１．１nm／Ｃｏ₈₁Ｆｅ₉ Ｐｄ₁₀１nm）₁₆人工格子膜を形成した。人工格子膜の成膜は、基板に直流バイアスを印加しながら行った。印加する直流バイアスの大きさを変えて抵抗変化率を測定し、基板に印加する直流バイアスの依存性（バイアス依存性）を図５６に示す。
【０２５０】
図５６から分かるように、直流バイアスを増加させるにしたがって抵抗変化率は増加し、バイアス−５０Ｖでは約２８％の極大値を示す。さらに、直流バイアスを大きくした場合には抵抗変化率は減少する。
【０２５１】
直流バイアスを変化させて作製した種々の人工格子膜の結晶性を評価したところ、全ての人工格子膜の主成長面はｆｃｃ相（１１１）面成長であった。ここで、積層周期（２．１ｎｍ）から反射された２θ＝４°付近に現れる長周期構造反射強度および２θ＝４４°付近に現れるｆｃｃ相（１１１）面から反射される主成長面のピーク強度について、それぞれのバイアス依存性を図５７および図５８に示す。
【０２５２】
図５７から分かるように、長周期構造反射強度のバイアス依存性については、バイアス−２０Ｖ程度に若干の極大を示すが、特にバイアスと強い相関があるとは言えない。また、図５８から分かるように、ｆｃｃ相（１１１）面反射強度のバイアス依存性についても、バイアス−１０Ｖ付近に若干の極大を示すが、バイアスと強い相関があるとは言えない。
【０２５３】
また、強磁性膜としてＣｏＦｅ合金系を用いていることにより、スピン依存散乱のバルク散乱が大きくなり、強磁性膜としてＣｏ系膜を用いる場合に比べて界面の構造は敏感でなくなる。なお、強磁性膜としてＣｏ系膜を用いる場合、抵抗変化率は膜構造に大きく依存することが報告されている。
【０２５４】
次に、保磁力（Ｈｃ）のバイアス依存性を図５９に示す。図５９から分かるように、バイアス−５０Ｖ程度までは２００Ａ／ｍ以下の良好な軟磁気特性を示すが、−６０Ｖ程度から保磁力が増加し始める。したがって、印加する直流バイアスの大きさを選択することにより、抵抗変化率および保磁力の最適条件を選ぶことができる。なお、ガラス基板の代わりにＳｉ基板、セラミック基板、ＧａＡｓ基板、Ｇｅ基板を用いた場合でも、同様にして抵抗変化率と保磁力の最適点を選び出すことができた。
【０２５５】
（実施例３２）
ここでは、スピン依存散乱能力を有する２つの強磁性膜両者の磁化回転により信号磁界を検出する本発明の実施例について説明する。
【０２５６】
図６０に示すように、基板８０上に反強磁性膜の配向制御用の下地膜８１、反強磁性膜８２、スピン依存散乱能力を有する強磁性膜８３、非磁性膜８４、強磁性膜８５、および反強磁性膜８２を順次形成した。さらに、最上層の反強磁性膜８２上に電極端子８６を形成した。この反強磁性膜８２上に必要に応じて保護膜を形成してもよい。なお、下地膜８１の材料は、反強磁性膜８２がＦｅＭｎからなる場合にはＣｕ、ＣｕＶ、ＣｕＣｒ等のＣｕ合金や、Ｐｄ等の非磁性ｆｃｃ相またはＮｉＦｅやＣｏＦｅＴａ等の磁性ｆｃｃ相を有する金属が望ましい。このとき磁性材料のほうが膜厚が薄くても（すなわちシャント分流が少ない）、良好な交換バイアスが付与できる。反強磁性膜８２はＦｅＭｎ、ＮｉＯ、ＰｔＭｎ等からなり、その膜厚は５〜５０nmである。強磁性膜８３，８５はＮｉＦｅ、Ｃｏ、ＣｏＦｅ、ＮｉＦｅＣｏ等からなり、その膜厚は０．５〜２０nmである。非磁性膜８４はＣｕ、Ａｕ、Ａｇ等からなり、その膜厚は０．５〜１０nmである。また、反強磁性膜８２は、強磁性膜８５の全面に形成する必要はなく、強磁性膜８３の両サイドのエッジ部（電極端子８６近傍）にのみ形成してもよい。
【０２５７】
ここで、少なくとも強磁性膜８３の成膜中には一方向の静磁界を図６０中のｘ方向（センス電流方向）に加える。その結果、強磁性膜８３に交換結合バイアス磁界がその静磁界方向に加わる。一方、少なくとも反強磁性膜８２の成膜中には強磁性膜８３の成膜中に加えた磁界方向とは１８０°異なる方向（マイナスｘ方向）に静磁界を加える。その結果、強磁性膜８３とは１８０°異なる方向に強磁性膜８５に交換結合バイアス磁界が加わる。その結果、２つの強磁性膜８３，８５の磁化のなす角度は信号磁界０の状態では反平行になる。なお、信号磁界Ｈｓは図中のｙ方向に加わる。
【０２５８】
反強磁性膜８２により強磁性膜８３および８５に反対方向のバイアス磁界を印加する方法には、次に示す方法もある。２つの反強磁性膜８２としてそれぞれ異なるネール温度を有する膜を用い、これらのネール温度以上で静磁界熱処理を行い、降温中に両反強磁性膜８２のネール温度の中間の温度で静磁界の方向を１８０°反転させる。その結果、強磁性膜８３，８５には反対方向へのバイアス磁界が付与できる。
【０２５９】
本実施例では、従来のスピンバルブ構造の膜とは異なり、反強磁性膜からの交換バイアスが加わった強磁性膜の磁化回転を利用しているので、その交換バイアス磁界はバルクハウゼンノイズを抑制する程度のあまり強くない磁界であることが望ましい。例えば、適用ヘッドのトラック幅等に応じて異なるが最大でも５ｋＡ／ｍである。しかしながら、現状のスピンバルブ構造の膜では、ＦｅＭｎからなる反強磁性膜による交換バイアス磁界を用いるのが一般的であるが、この場合、ＦｅＭｎ膜とＮｉＦｅ膜等の強磁性膜とを直接積層すると１０ｋＡ／ｍ以上の交換バイアスが生じてしまう。その交換バイアスを低減させるためには、反強磁性膜と強磁性膜の中間に交換バイアス調整用の膜、例えば飽和磁化の低い強磁性膜や非磁性膜を挿入する方法や、図６１に示すように、強磁性膜８３と８５のそれぞれの膜中に非磁性膜８７，８８を介在させる、すなわち強磁性膜８３，８５をそれぞれ８３ａおよび８３ｂ，８５ａおよび８５ｂに分離する方法がある。
【０２６０】
強磁性膜中に非磁性膜を介在させる方法では、反強磁性膜８２と接する側の強磁性膜８３ａ，８５ａには強い交換バイアスが加わるが、反強磁性膜８２と接しない側の強磁性膜８３ｂ，８５ｂには弱い交換バイアスが加わる。非磁性膜８７，８８の材料の種類やその膜厚により、反強磁性膜８２と接しない側の強磁性膜８３ｂ，８５ｂへの交換バイアスの大きさを低減できる。
【０２６１】
ここで、強磁性膜８３ａおよび８３ｂの磁化のなす角度と、強磁性膜８５ａおよび８５ｂの磁化のなす角度は、信号磁界による磁化回転で強磁性的な配列から反強磁性的な配列に変化するが、膜中央部における強磁性膜８３ｂおよび８５ｂの磁化のなす角度は、逆に反強磁性的な配列から強磁性的な配列に変化する。したがって、前者と後者のスピン依存散乱は相殺される。そこで、強磁性膜８３ａ，８５ａおよび非磁性膜８７，８８の材料としては、スピン依存散乱能力がなく高抵抗のものであることが望ましい。さらに、反強磁性膜８２と接する側の強磁性膜８３ａ，８５ａの厚みは、反強磁性膜８２と接しない側の強磁性膜８３ｂ，８５ｂの厚みに比べて小さくすることが望ましい。
【０２６２】
上記のようにすることにより、磁界０で強磁性膜８３および８５の磁化方向を反平行に揃えることができる。その結果、第１に、磁気ヘッドに適する困難軸方向（図中ｙ方向）に信号磁界を加えた場合でも、両強磁性膜の磁化回転により両強磁性膜間の磁化のなす角度が０〜１８０°まで変化する状態が実現でき、容易軸方向と同程度の高い抵抗変化率を実現できる。第２に、２つの強磁性膜にバイアス磁界が加わるので、両強磁性膜から磁壁を無くすことができ、バルクハウゼンノイズを抑制できる。第３に、センス電流と信号磁界が直交する方式では、従来スピンバルブ構造では相殺されていたＮｉＦｅ膜等を用いた場合に顕著である通常の磁気抵抗効果とスピン依存散乱による抵抗変化とを兼ねることができ、△Ｒ／Ｒの増大が期待できる。
【０２６３】
（実施例３３）
実施例３２では、２つの反強磁性膜を用いて両強磁性膜の磁化を反平行にする方法を示した。しかし、必ずしも反強磁性膜のみでバイアス磁界を加える必要はなく、硬質磁性膜からの漏れ磁界や微細形状に加工した場合に生じる反磁界を利用しもよい。次に、その一例について説明する。
【０２６４】
図６２から分かるように、基板９０上にスピン依存散乱能力を有する強磁性膜９１、非磁性膜９２、および強磁性膜９３を形成した。強磁性膜９１，９３および非磁性膜９２の膜厚は実施例３２と同様とした。その上に厚さ２〜５０nmの反強磁性膜９４を形成し、強磁性膜９３に交換バイアスを印加した。さらに、その上に厚さ１０〜５０nmのＣｏＰｔ、ＣｏＮｉからなる硬質磁性膜９５を形成した。硬質磁性膜９５の上に電極端子９６を形成した。成膜はすべて静磁界（図中ｘ方向）中で行った。
【０２６５】
次いで、反強磁性膜９４による交換バイアス磁界方向と同じ方向に４００〜８００ｋＡ／ｍの磁界を加えて硬質磁性膜９５をｘ方向に着磁した。その結果、硬質磁性膜９５のエッジ部からの洩れ磁界により強磁性膜９１にはマイナスｘ方向にバイアス磁界が加わり、強磁性膜９１と９３の磁化は反平行状態になった。なお、強磁性膜９３にも硬質磁性膜９５からのバイアス磁界が加わるが、反強磁性膜９４からの交換バイアス磁界の方が強くなるように交換バイアス力を設定することにより、前述した反平行磁化状態を実現できる。なお、硬質磁性膜９５と反強磁性膜９４を強磁性膜９３の全面に形成する必要はなく、強磁性膜９３のエッジ部（電極端子９６近傍）のみに形成してもよい。
【０２６６】
なお、図６２の９５には硬質磁性膜の代わりに軟磁性に近い強磁性膜を用いることもできる。この場合、軟磁性に近い強磁性膜は、反強磁性膜９４から交換バイアスが加わるように積層する必要がある。強磁性膜９５に交換バイアスが加わると、強磁性膜９５の磁化を一方向に固着できるので、信号磁界等の外部磁界が加わっても安定した静磁結合バイアス磁界を強磁性膜９１に、磁気抵抗効果に不可欠な微細パターン形状に加工することにより強磁性膜９３に加わる反強磁性膜９４からの交換バイアス磁界と１８０°異なる方向に付与できる。このとき、強磁性膜９５の膜厚や飽和磁化を調整することにより、所望の強度のバイアス磁界を強磁性膜９１に付与できる。
【０２６７】
また、強磁性膜９５の抵抗率や膜厚を調整することにより、所望のシャント分流動作点バイアスが付与できる。ここで、強磁性膜９５では、反強磁性膜９４と交換結合するのに要求される特性（反強磁性膜９４とエピタキシャル成長するために反強磁性膜９４と結晶構造や格子定数が同様である結晶性の強磁性膜、例えばＮｉＦｅ膜、ＣｏＦｅ膜、ＣｏＦｅＴａ膜、ＣｏＦｅＰｄ膜が望ましい）と、静磁結合バイアスや動作点バイアスに要求される特性とを両立することが困難である（上記結晶性の膜では抵抗率が低すぎる）。そこで、強磁性膜９５は、反強磁性膜９４と接する交換結合用磁性膜（ＮｉＦｅやＣｏＦｅ系強磁性膜等）とバイアス用の強磁性膜（Ｃｏ系非晶質膜、ＦｅＴａＮ等の窒化微結晶膜、あるいはＦｅＺｒＣ等の炭化微結晶膜等）が界面で強磁性交換結合する２層構造であることが望ましい。
【０２６８】
図６２に示す構造の場合、硬質磁性膜９５に電極端子９６からのセンス電流が分流するのでΔＲ／Ｒがある程度減少することが避けられない。この問題は図６３〜図６５に示す構造により解消できる。
【０２６９】
すなわち、図６３に示すように、基板９０上に図６２と同様に反強磁性膜９４まで成膜し、その後、反強磁性膜９４の両サイド近傍に硬質磁性膜９５を形成する。その内側にトラック幅に相当する間隔で電極端子９６を形成する。その結果、硬質磁性膜９５にセンス電流が流れることを防止でき、ΔＲ／Ｒの低下を抑制できる。
【０２７０】
一方、図６４に示すように、基板９０上の最初に硬質磁性膜９５を形成し、その上に絶縁膜９７を介して強磁性膜９１、非磁性膜９２、強磁性膜９３、および反強磁性膜９４を順次形成し、さらに電極端子９６を形成する。このとき、成膜中に静磁界を加えて、反強磁性膜９４から強磁性膜９３に所定の交換バイアス磁界を加える。成膜後にこの交換バイアス方向と同じ方向に硬質磁性膜９５を着磁する。この方法でも、強磁性膜９１と９３に反対方向のバイアス磁界を印加することができ、しかも硬質磁性膜９５に電流が流れることを防止できる。なお、絶縁膜９７は硬質磁性膜９５と強磁性膜９１との交換結合により過大なバイアス磁界が加わることを防ぐ効果もある。
【０２７１】
また、図６５に示すように、基板９０上に強磁性膜９１、非磁性膜９２、強磁性膜９３、および反強磁性膜９４を順次成膜する。次に、この積層膜を所定の形状に微細加工する。この微細加工はレジスト等を用いてマスクを形成し、イオンミリング等により行う。この後、この残りのマスクを使用してリフトオフ法により強磁性膜９１のサイドに硬質磁性膜９５を形成する。最後に、強磁性膜９３に加わる交換バイアスとは逆方向に硬質磁性膜９５を着磁する。この方法でも、強磁性膜９１と９３に反対方向のバイアス磁界を印加することができ、しかも硬質磁性膜９５に電流が流れることを防止できる。
【０２７２】
（実施例３４）
図６１に示すスピンバルブ構造において、ガラス基板８０上に１at% のＣｒを含む厚さ５nmのＣｕ下地膜、反強磁性膜８２として厚さ１５nmのＦｅＭｎ膜、強磁性膜８３ａとして厚さ１nmのＮｉ₈₀Ｆｅ₂₀膜、非磁性膜８７として１at% のＣｒを含む厚さ１．５nmのＣｕ膜、強磁性膜８３ｂとして厚さ６nmのＮｉ₈₀Ｆｅ₂₀膜、非磁性膜８４として厚さ２．５nmのＣｕ膜、強磁性膜８５ｂとして厚さ６nmのＮｉ₈₀Ｆｅ₂₀膜、非磁性膜８７として１at% のＣｒを含む厚さ１．５nmのＣｕ膜、強磁性膜８５ａとして厚さ１nmのＮｉ₈₀Ｆｅ₂₀膜、並びに反強磁性膜８２として厚さ１５nmのＦｅＭｎ膜を順次形成した。
【０２７３】
これらの膜の成膜は、永久磁石による静磁界中で２極スパッタリング法により真空を破ることなく一括に行った。なお、この永久磁石は基板ホルダーには一体的に取り付けられていない。また、このとき、予備排気圧１×１０^-4Ｐａ以下、Ａｒガス圧０．４Ｐａの条件で行い、強磁性膜８３の成膜が終了した後で基板ホルダーを１８０°回転させて永久磁石によるバイアス磁界（約４０００Ａ／ｍ）の方向を１８０°反転した。このようにして、信号磁界０で両強磁性膜磁化の反平行状態を実現できるスピンバルブ構造の積層膜を作製した。
【０２７４】
得られた積層膜の抵抗を４端子法により測定した。具体的には、強磁性膜８３および８５の容易軸方向に１ｍＡの定電流を加え、困難軸方向の膜の幅を１mmとして４mm間の電圧を測定した。磁界はヘルムホルツコイルにより強磁性膜８３および８５の困難軸方向に加えた。その結果、得られた抵抗−磁界特性を図６７に示す。
【０２７５】
図６６において、抵抗は最大磁界（１６ｋＡ／ｍ）での値を１に規格化して示す。磁界０では強磁性膜８３と８５の磁化が反平行状態にあるので、抵抗が最大値を示す。磁界が加わると、急激に抵抗は低下する。特に、２０００Ａ／ｍ以上の磁界では抵抗はおよそ一定値を示す。約３．８％以下の抵抗変化率が２０００Ａ／ｍ以下の僅かの磁界範囲で生じることが分かる。また、この抵抗−磁界特性にはヒステリシスやノイズが殆ど認められない。すなわち、このスピンバルブ構造の積層膜を用いると、著しく高感度でノイズの少ない磁気ヘッドを得ることができる。
【０２７６】
さらに、図６０に示すスピンバルブ型磁気抵抗効果素子を作製して、非磁性層８４（Ｃｕ）の厚みと抵抗変化率との関係を調べた。その結果を下記表６に示す。下地膜には厚さ５nmのＮｉＦｅ膜を用い、強磁性膜８３，８５には厚さ８nmのＮｉＦｅ膜を用い、反強磁性膜８２には厚さ１０nmのＦｅＭｎ膜を用いた。
【０２７７】
【表６】

【０２７８】
表６から分かるように、Ｃｕ厚が薄くなると急激に抵抗変化率が増加して、Ｃｕ厚が１．２nmでは９％の高い抵抗変化率が得られた。これは、強磁性膜８３と強磁性膜８５には５０ｋＡ／ｍの比較的大きな反平行バイアス磁界がそれぞれに加わっているので、非磁性膜８４の厚みを薄くしても安定した反強磁性磁化配列が実現できるためである。非磁性層（Ｃｕ）厚を２nm未満に薄くする場合、反平行磁化配列が崩れて抵抗変化率が激減する従来のスピンバルブ型磁気抵抗効果素子と異なり、両方の強磁性膜８３，８４に反対方向のバイアス磁界を加え、非磁性膜８４の厚みを薄くすることにより大幅に抵抗変化率を増大できる。
【０２７９】
（実施例３５）
次に、スピン依存散乱能力を有する強磁性膜の数を３層以上に増やした場合について説明する。
【０２８０】
図６７に示すように、基板１００上に反強磁性膜１０２の配向を制御するための下地膜１０１、ＦｅＭｎ、ＮｉＯ、ＰｔＭｎ等からなる厚さ５〜５０nmの反強磁性膜１０２、ＣｏＦｅ、Ｃｏ、ＮｉＦｅ等からなる厚さ１〜２０nmの強磁性膜１０３、Ｃｕ、Ａｕ等からなる厚さ１〜１０nmの非磁性膜１０４、厚さ１〜２０nmの強磁性膜１０５、厚さ１〜１０nmの非磁性膜１０６、厚さ１〜２０nmの強磁性膜１０７、および厚さ５〜５０nmの反強磁性膜１０８を形成した。ここで、強磁性膜１０３，１０５，１０７の膜厚は、すべて等しくても異なっていてもよい。さらに、その上に必要に応じて保護膜を形成して電極端子１０９を形成した。なお、成膜は静磁界中で行った。
【０２８１】
反強磁性膜１０２と１０８からそれぞれ強磁性膜１０３と１０７に交換バイアスを一方向（図中ｘ方向）に加えた。その結果、中間の強磁性膜１０５のみが透磁率が高く、強磁性膜１０３と１０７は低い透磁率、すなわち磁化の固着が実現できた。この磁化の固着には、反強磁性膜ではなく図６３で示したような硬質磁性膜９５を用いてもよい。なお、反強磁性膜１０２および１０８と接する強磁性膜１０３および１０７の材料として軟磁性があまり良好でないが抵抗変化率の高いＣｏやＣｏＦｅを用い、中間の強磁性膜１０５の材料として抵抗変化率はあまり高くないが軟磁性が良好であるＮｉＦｅを用いることにより低磁界で高い抵抗変化率を実現できる。
【０２８２】
このような構成により、中間の強磁性膜１０５の磁化回転が低磁界で容易に起こり、また、非磁性層を介した界面数が従来のスピンバルブ構造の膜に比べて２倍に増えるので、低磁界で従来のスピンバルブ構造の膜を上回る抵抗変化率を実現できる。また、この積層膜の中央に信号磁界で磁化回転する強磁性膜が位置することになるので、センス電流磁界による強磁性膜の磁化の乱れは僅かであり、安定した信号検出が可能になる。なお、実施例３３で説明したような硬質磁性膜や反磁界によるバイアス法を併用すれば、強磁性膜１０３および１０７と、中間の強磁性膜１０５の磁化のなす角度を信号磁界０で反平行にすることができる。その結果、実施例３２で述べた種々の効果により、さらに高感度で低ノイズの磁気抵抗効果素子を得ることができる。
【０２８３】
（実施例３６）
図６８は、スピン依存散乱能力を有する強磁性膜の数を４層に増やした積層膜を示す。
【０２８４】
基板１００上に、反強磁性膜１１１、非磁性層１１３，１１５，１１７を介して積層した４層の強磁性膜１１２，１１４，１１６，１１８、反強磁性膜１１９を順次形成して、センス電流が信号磁界と同方向に流れるように電極端子１０９をその上に形成した。必要に応じて反強磁性膜１１１の下には配向制御用の下地膜を、反強磁性膜１１９の上には保護膜を形成する。各膜の材料、膜厚は図６７に示したものと同様とした。
【０２８５】
少なくとも強磁性膜１１２の成膜中には静磁界を図中ｘ方向（トラック幅方向）に付与して、一方、その後の成膜途中で静磁界方向１８０°反転して少なくとも反強磁性膜１１９の成膜中には静磁界を図中マイナスｘ方向に付与した。この成膜中の静磁界により、強磁性膜１１２にはｘ方向に、強磁性膜１１８にはマイナスｘ方向に交換バイアス磁界による磁化固着を生じる。また、この構成では、トラック幅が狭いと強磁性膜１１２，１１４，１１６，１１８の幅も同様に狭くなるので、その方向に強い反磁界が発生する。この反磁界により、反強磁性膜と接していない中間の強磁性膜１１４と１１６の磁化はそれぞれ強磁性膜１１２と１１８の磁化と反平行になる。すなわち信号磁界０では４層の強磁性膜の隣接する磁化は互いに反平行に向くことになる。
【０２８６】
なお、中間の強磁性膜１１４と１１６への反磁界が不充分の場合には、センス電流により発生する磁界が強磁性膜１１２と１１４ではマイナスｘ方向に、強磁性膜１１６と１１８ではｘ方向に加わるようにセンス電流を図中ｙ方向に加えることが望ましい。ここで、反強磁性膜からの交換バイアス磁界をセンス電流磁界よりも大きくなるように設定すれば、強磁性膜１１２と１１８の磁化を電流磁界により乱されることなく反強磁性膜からの交換バイアス方向に固着できる。
【０２８７】
このような構成にすることにより、４層の強磁性膜の各磁化方向は、信号磁界０で反強磁性的に配列できる。したがって、界面数の増加に対応してΔＲ／Ｒが増加する。また、信号磁界が僅かに加わることにより各層の磁化が回転できるので、高感度なスピン依存散乱を用いた磁気抵抗効果素子を実現できる。
【０２８８】
（実施例３７）
次に、スピン依存散乱能力を有する一部の強磁性膜の磁化を固着して、残りの強磁性膜の磁化を信号磁界０で信号磁界方向と異なる方向に配列する場合について説明する。
【０２８９】
図６９は、センス電流と信号磁界の方向が直交する積層膜を示す。基板１２０上に、非磁性膜１２２を介在させたスピン依存散乱能力を有する強磁性膜１２１および１２３の積層膜、反強磁性膜１２４を順次形成した。各膜の材料、厚みは図６０に示したものと同様とした。必要に応じて、反強磁性膜１２４上に保護膜を形成した後に電極端子１２５を形成した。
【０２９０】
ここで、少なくとも強磁性膜１２１の成膜中には、図中ｘ軸およびｙ軸の２等分線の方向に静磁界を付与し、一方、少なくとも反強磁性膜１２４の成膜中には、その静磁界の方向を前者の方向と４５°回転させて付与した（図中ｙ方向）。その結果、強磁性膜１２１の磁化は前記静磁界のｘ方向に付与され、強磁性膜１２３の磁化は反強磁性膜１２４からのバイアス磁界により信号磁界方向に固着された。このような構成によれば、信号磁界０では両強磁性膜の磁化のなす角度は４５°になり、信号磁界が強磁性膜１２３の磁化固着方向に加わると、両強磁性膜の磁化方向が強磁性的な配列になるため抵抗が減少し、逆に磁化固着方向と１８０°異なる方向に信号磁界が加わると、両強磁性膜の磁化方向が反強磁性的な配列になるため抵抗が増大する。したがって、線型応答を実現するために従来の磁気抵抗効果素子に必要であった動作点バイアスが不要になる。なお、この方法では、強磁性膜１２１と１２３との強磁性的な結合により強磁性膜１２１の磁化が信号磁界０でｙ方向に向けて傾き易く、大きな信号磁界が加わると再生信号が歪み易い傾向がある。これは、センス電流により発生する電流磁界が、強磁性膜１２１ではこの強磁性的な結合方向と１８０°異なる方向に加わるように、すなわちこの強磁性的な結合による磁界と電流磁界が相殺されるようにセンス電流の流れる向きを決めることにより回避できる。
【０２９１】
しかしながら、強磁性膜１２１や１２３に異方性磁気抵抗効果を有する膜を用いる場合には、逆にこの強磁性的な結合による磁界により強磁性膜１２１の磁化Ｍが強磁性膜１２３の磁化Ｍ方向に傾くと、磁気異方性とスピン異存散乱による抵抗変化が重畳するので（電流方向がｘ方向であるため）感度向上が期待できる利点がある。実際に、磁気抵抗効果素子が用いられる状況に応じて、強磁性膜１２１の磁化方向を電流方向等の手段により調整する必要がある。
【０２９２】
ところで、実施例３７では、バルクハウゼンノイズ抑制に必要な縦バイアス磁界（図中ｘ軸およびｙ軸の２等分線方向のバイアス磁界）を加える必要がある。このためには、実施例３２に示したような反強磁性膜を強磁性膜１２１の基板側に配置して交換結合させる。あるいは、図７０（Ａ）に示すように、反強磁性膜１２４上に、ある程度軟磁性が良い（Ｈｃが交換バイアス磁界Ｈ_UAより小さい）強磁性膜１２６を積層して、少なくともこの強磁性膜１２６の積層中には、成膜中のバイアス磁界方向を概ね１３５°反転して強磁性膜１２６からの交換バイアス磁界を強磁性膜１２１に加える方法がある。この場合には、スピン依存散乱ユニットである膜が下地膜の役目も果たすので、反強磁性膜１２４上に成膜した強磁性膜１２６に容易に交換バイアスを付与できる。その結果、実際に再生ヘッドに適した微細パターンに加工したときに発生する静磁結合磁界（反磁界）により、縦バイアス磁界を強磁性膜１２１に加えることができるので、バルクハウゼンノイズが抑制できる。
【０２９３】
図７０（Ａ）の実施例では、反強磁性膜１２４の膜面両サイドで交換バイアス方向が異なるので、バイアス磁界方向が不安になる場合もある。これは、図７０（Ｂ）に示すように、反強磁性膜１２４を中間に磁気結合を弱めるが結晶成長を阻害しない極薄い中間膜１２４ｂ（Ｃｕ等のｆｃｃ相膜）を介して反強磁性膜１２４ａと１２４ｃに分離することで回避できる。このとき、実施例３２で述べたように、熱処理で交換バイアス磁界方向を制御可能とするため、反強磁性膜１２４ａと１２４ｃはネール点またはブロッキング温度が異なる材料で構成されることが好ましい。さらに、強磁性膜１２６が厚く、Ｂｓが高くないと所望の縦バイアス磁界が強磁性膜１２１に付与できないが、このとき強磁性膜１２６にセンス電流が分流するので、強磁性膜の抵抗率は高いことが望ましい。具体的には、Ｃｏ系やＦｅ系のアモルファス膜や窒化または炭化微結晶膜を用いることが望ましい。しかしながら、このような膜は、ＦｅＭｎ等の反強磁性膜と交換結合し難いので、反強磁性膜１２４ａと接する部分には極薄いＮｉＦｅやＣｏＦｅＴａ等の交換結合しやすい強磁性膜１２４ｂを積層して、その上に高抵抗のアモルファス的な高Ｂｓ強磁性膜１２６ａを強磁性交換結合するように積層することが望ましい。
【０２９４】
（実施例３８）
図７０（Ｃ）は、センス電流と信号磁界の方向が平行である積層膜を示す。センス電流の流れる方向が異なり、強磁性膜１２１の磁化が図中ｘ方向に付与され、かつ膜の長手方向が９０°回転していること以外は図６９の構成と同様である。この構成においては信号磁界０では両強磁性膜の磁化のなす角度は９０°になり、信号磁界が強磁性膜１２３の磁化固着方向に加わると、両強磁性膜の磁化が強磁性的な配列になるため抵抗が減少し、逆に磁化固着方向と１８０°異なる方向に信号磁界が加わると両強磁性膜の磁化が反強磁性的な配列になるため抵抗が増大する。したがって、やなり、動作点バイアスが不要になる。この構成では、センス電流による電流磁界が強磁性膜１２１の容易軸方向であり、この磁界がバルクハウゼンノイズを抑制する効果がある。
【０２９５】
さらに、実施例３８では、強磁性膜１２３から発生しやすいフェロ結合磁界のために強磁性膜１２１の磁化がｙ方向に傾きやすいことを付け加えておく。実施例３７で詳しく説明したように、この強磁性的結合磁界は、信号磁界ダイナミックレンジが縮まるが、異方性磁気抵抗効果を重畳する利点を有する。なお、電流磁界が強磁性膜１２１に加わるので、必ずしも強磁性膜１２１の容易軸がｘ方向にある必要はない。
【０２９６】
バルクハウゼンノイズ抑制効果が不十分のときは、強磁性膜１２３の磁化固着方向を信号磁界方向から外すことにより、図中ｘ方向に静磁結合磁界が発生してより強いバルクハウゼンノイズ抑制磁界を付与できる。
【０２９７】
（実施例３９）
図７１は、スピン依存散乱能力を有する強磁性膜を３層とした場合の積層膜を示す。図７１では、センス電流と信号磁界が直交する場合について示す。基板１３０上に、静磁界中で反強磁性膜１３１、非磁性膜１３３および１３５を介在させたスピン依存散乱能力を有する強磁性膜１３２，１３４，１３６の積層膜、反強磁性膜１３７を順次形成した。その上に電極端子１３８を形成した。
【０２９８】
ここで、静磁界の方向は、少なくとも強磁性膜１３２と反強磁性膜１３７の成膜中は同じ方向として（図中ｙ方向）、強磁性膜１３４の成膜中はそれと４５°の角をなす方向（図中ｘ軸とｙ軸の２等分線方向）とした。その結果、強磁性膜１３２と１３６の磁化は図中ｙ方向に固着され、強磁性膜１３４の磁化は高透磁率を保ち、磁界０では図中ｘ軸とｙ軸の２等分線方向近傍に向く。したがって、この構成でも、磁界０では両強磁性膜の磁化のなす角度はほぼ４５°になり、信号磁界が強磁性膜１３６の磁化固着方向に加わると、両強磁性膜の磁化方向が強磁性的な配列になるため抵抗が減少し、逆に磁化固着方向と１８０°異なる方向に信号磁界が加わると、両強磁性膜の磁化方向が反強磁性的な配列になるため抵抗が増大する。すなわち、動作点バイアスが不要になる。この構成では界面数が２倍に増えるので感度も向上する。
【０２９９】
（実施例４０）
実施例３８で示した方法の磁気抵抗効果素子の積層膜の抵抗−磁界特性を説明する。
【０３００】
図７０（Ｃ）において、基板１２０としてサファイアＣ面基板を用い、強磁性膜１２１として厚さ５nmのＰｄ下地膜を有する厚さ６nmのＣｏ₉₀Ｆｅ₁₀膜を用い、非磁性膜１２２として厚さ３nmのＣｕ膜を用い、強磁性膜１２３としては厚さ４nmのＣｏ₉₀Ｆｅ₁₀膜を用い、反強磁性膜１２４としては厚さ１５nmのＦｅＭｎ膜を用い、さらに、その上に保護膜として厚さを５nmのＰｄ膜を形成した。
【０３０１】
この積層膜は２極スパッタリング法により真空を保ったまま一括に成膜した。なお、成膜中には永久磁石により静磁界を付与し、強磁性膜１２１の成膜を終えた後に静磁界の方向を９０°反転させて、強磁性膜１２１と１２３の容易軸のなす角度を９０°とした。また、スパッタリングの予備排気は１×１０^-4Ｐａ以下、スパッタガス圧は０．４Ｐａとした。
【０３０２】
この積層膜の抵抗−磁界特性を実施例３３と同様に測定した。図７２に困難軸方向の抵抗−磁界特性を示す。図７２において、強磁性的な磁化配列での抵抗を１として規格化する。図７２から分かるように、信号磁界０で線形性のよい抵抗の磁界変化が得られる。これにより、動作点バイアスが不必要であることが分かる。
【０３０３】
（実施例４１）
ここでは、強磁性膜／非磁性膜／強磁性膜からなるスピン依存散乱ユニットの両強磁性膜に別の強磁性膜または反強磁性膜を２層以上積層して、そのとき発生する両バイアス磁界を概ね直交させた磁気抵抗効果素子の実施例を示す。
【０３０４】
図７３は、基板１２０上に、ＣｏＰｔ等のハード強磁性膜、一軸磁気異方性磁界Ｈｋがスピン依存散乱ユニットの強磁性膜よりも大きな高Ｈｋ強磁性膜（例えば、Ｈｋ〜５ｋＡ／ｍのＣｏＦｅＲｅ膜等）やＮｉＯ等の反強磁性膜からなるバイアス磁界を印加するための第１のバイアス膜１２１ａ、スピン依存散乱ユニット（強磁性膜１２１、非磁性膜１２２、強磁性膜１２３）、ＦｅＭｎ等の反強磁性膜からなるバイアス磁界を印加するための第２のバイアス膜１２４を順次積層した多層膜を示す。この多層膜の第１のバイアス膜１２１ａから発生するバイアス磁界は、積層界面を通した交換結合により主に強磁性膜１２１にバイアス磁界が加わる。一方、第２のバイアス膜１２４から発生するバイアス磁界は、積層界面を通した交換結合により主に強磁性膜１２３に加わる。この第１と第２のバイアス磁界は概ね直交するような方向関係を満足するように加える。さらに、第２のバイアス磁界は強磁性膜１２３の磁化が信号磁界で実質的に動けない程度の強い値とする（１０ｋＡ／ｍ以上が望ましい）。
【０３０５】
一方、第１のバイアス磁界強度は、信号磁界により強磁性膜１２１の磁化が回転でき、バルクハウゼンノイズが抑制できる程度の磁界とする。具体的には、第１のバイアス膜に反強磁性膜を用いる場合には、バイアス膜１２１ａと強磁性膜１２１のバイアス磁界を５ｋＡ／ｍ以下にすることが望ましい。第１のバイアス膜に強磁性膜を用いる場合には、何等かの手段によりバイアス膜１２１ａの磁化方向を一定方向に保持して単磁区化してバイアス膜１２１ａと強磁性膜１２１を強い交換結合で一体化すると、信号磁界によりバイアス膜１２１ａおよび強磁性膜１２１が概ね同様に回転でき、強磁性膜１２１ａが単磁区であるので、強磁性膜１２１も単磁区になりバルクハウゼンノイズが除去できる。あるいは、例えば界面に別の層を挿入してバイアス膜１２１ａと強磁性膜１２１の交換結合〜５ｋＡ／ｍ以下に弱める方法もある。この場合、強磁性膜１２１のみが信号磁界により磁化回転するため、バイアス膜１２１ａの透磁率を抑制して磁化を動き難くすることが好ましい。この透磁率抑制手段としては、Ｈｋの向上、保磁力の向上、あるいは何等かの手段で一方向性バイアス磁界をバイアス膜１２１ａに加える等がある。
【０３０６】
ここで、強磁性膜１２１ａを単磁区化する手段としては、図７４に示すように、バイアス膜１２１ａをスピンバルブユニットよりも長くしてバイアス膜１２１ａのエッジ部に新たな反強磁性膜やハード膜１２１ｂを積層することが等が可能である。
【０３０７】
以上の構成の磁気抵抗効果素子を作製すると、強磁性膜１２３の磁化方向は固定され強磁性膜１２１の磁化が信号磁界に応じて変化するので、図６９に示した実施例と同様に信号磁界〜０で線形性の良好な高感度な磁気抵抗効果素子が得られ、なおかつ信号磁界を検出する強磁性膜１２１の磁壁も除去できるので、動作点バイアスが不要で高感度・ノイズなしの信号磁界再生が可能になる。
【０３０８】
ここで、強磁性膜１２１の磁化容易軸方向をバイアス磁界方向と直交する方向に付与することが、特に磁気異方性の大きなＣｏ系の強磁性膜を１２１に用いた場合には望ましい。そうすると、異方性磁界に相当する飽和磁界とバイアス磁界が相殺できるので、Ｈｓが大幅に低減できるので、図６９に示した飽和磁界−抵抗特性の傾きが急峻になり、通常のバイアス磁界方向と強磁性膜１２１の磁化容易軸が同方向である場合に比べて、より高感度な信号磁界検出が可能になる。バイアス磁界と強磁性膜の容易軸の方向を変えるには、バイアス膜１２１ａの成膜中における磁界印加方向と強磁性膜１２１の成膜中における磁界付与方向を変える方法等がある。
【０３０９】
（実施例４２）
図７５に示すように、支持基板１４０上に、高保磁力膜の配向を制御するための厚さ２０nmのＣｒ下地膜１４１、Ｃｏ等からなる厚さ８nmの高保磁力膜１４２、Ｃｕ等からなる厚さ３nmの非磁性膜１４３、および厚さ４．６nmのＮｉＦｅ等からなる強磁性膜１４４を順次形成し、さらに、その上に電極端子１４５を形成してスピンバルブ構造の磁気抵抗効果素子を作製した。なお、積層膜の成膜は超高真空Ｅガン蒸着により行った。このときの基板温度は約１００℃とし、真空チャンバー内は１×１０^-8Ｐａ以下に排気した。
【０３１０】
基板温度約１００℃とした場合のＣｏ／Ｃｒ膜についてＸ線回折パターンを調べた。その結果を図７６に示す。図７６に示すように、この膜はＣｒ（２００）が高配向であり、このＣｒ膜を下地膜としたＣｏ膜も（１１０）が高配向であった。なお、Ｃｏ（１１０）ピークのロッキングカーブ半値幅は約３°であった。
【０３１１】
次に、基板温度約１００℃で成膜した図７５に示すＮｉＦｅ／Ｃｕ／Ｃｏ／Ｃｒ／基板の構造の積層膜の困難軸方向のＲ−Ｈカーブを図７７に示す。Ｒ−Ｈカーブは通常のレジストプロセス、イオンミーリングを用いて積層膜を２mm×６μｍのパターンに加工し、４端子法により測定した値に基づいて作成した。このとき、容易軸はパターン長手方向とし、磁界はパターン幅方向に加えた。
【０３１２】
図７７に示すように印加磁界±８０Ｏｅの場合、抵抗変化率約６．５％となり、飽和磁界は約３．６ｋＡ／ｍとなった。
【０３１３】
この構造は、高保磁力膜のＨｃが約８ｋＡ／ｍであるため、媒体からの磁界が８ｋＡ／ｍ未満の場合は問題がないが、ヘッドと媒体との間が近い構造、すなわち媒体からの磁界が８ｋＡ／ｍ以上となるような構造には適さない。そこで、図７５と同様の構造、膜厚で、基板温度を約２００℃とし、さらに約８ｋＡ／ｍの磁界中で積層膜を成膜した。
【０３１４】
基板温度約２００℃とした場合のＣｏ／ＣｒのＸ線回折パターンは図７６とほぼ同じであった。また、この積層膜もＣｏ（１１０）ピークのロッキングカーブ半値幅は約３°であった。さらに、ポールフィギュアで測定したところ磁界方向に六方晶Ｃ軸の偏りが見られた。したがって、基板温度１００℃、無磁界中において成膜した積層膜に比べ、単結晶様のＣｏが得られた。
【０３１５】
次に、基板温度約２００℃、磁界中において成膜した図７５と同じ構造の積層膜の困難軸方向のＲ−Ｈカーブを図７８に示す。Ｒ−Ｈカーブは前記と同様に積層膜を２mm×６μｍのパターンに加工し、４端子法で測定した値に基づいて作成した。このとき容易軸（Ｃ軸の方向）はパターン長手方向とし、磁界はパターン幅方向に加えた。
【０３１６】
図７８に示すように、外部磁界±１．６ｋＡ／ｍの場合でも高保磁力膜の磁化は印加磁界によってほとんど動くことはなく、しかもＮｉＦｅ膜の飽和磁界も約２．８ｋＡ／ｍと低く保つことができた。また、抵抗変化率も約７．５％となった。
【０３１７】
上記構成の積層膜は、外部磁界１．６ｋＡ／ｍでも高保磁力膜の磁化が安定しているため、ＮｉＦｅ膜の容易軸を幅方向として、ＣｏのＣ軸を概ね長手方向とするパターンを作製した。この構成により動作点バイアスが不要となる。このとき、磁界をパターン長手方向に加え、そのときのＲ−Ｈカーブを測定した。なお、パターン形状は前記と同様に２mm×６μｍとした。その結果を図７９に示す。図７９から分かるように、ヒステリシスのない良好なＲ−Ｈカーブが得られ、Ｈｋも約１．６ｋＡ／ｍと低い値を示した。
【０３１８】
また、ここでは高保磁力膜としてＣｏ膜を用いたが、ＣｏＮｉ膜、ＣｏＣｒ膜を用いてもよい。さらに、下地膜としてはＣｒ膜の他にＷ膜等を用いてもよく、これらのＣｒ，Ｗをベースとして、それに添加元素を加えてもよい。なお、この下地膜は、本発明全体にわたっていわゆるハード膜の下地膜に適用することができる。これにより、Ｃ軸を硬磁性膜の膜面内に存在させる（特定方向にＣ軸が揃う）ことができる。したがって、硬磁性膜を固着した場合に、その上に形成した強磁性膜まで固着されることを防止できる。
【０３１９】
ここで、参考のために下地膜のない積層膜のＭ−Ｈカーブを図８０に示す。Ｃｏの磁化の垂直成分から漏れ磁界が発生し、ＮｉＦｅ膜の軟磁気特性を劣化させていることが分かる。これは、一部のＮｉＦｅとＣｏの磁化が一体化していると考えられる。
【０３２０】
（実施例４３）
実施例４２で示すように、基板温度約２００℃で成膜した高保磁力膜は、単結晶様の膜で低抵抗であるため、電子の平均自由行程を高保磁力膜の厚みよりも充分に長くできる。したがって、図８１のように高保磁力膜１４２と強磁性膜１４４とをＣｕ非磁性膜１４３を介して積層した。この積層膜の抵抗変化率は約１５％と高い値を示した。なお、このような構造の積層膜を作製するためには、第１層の高保磁力膜１４２の配向を制御するために下地膜を設けることが望ましい。また、本実施例では下地膜として厚さ２０nmのＣｒ膜１４１を用いた。
【０３２１】
（実施例４４）
次に、配向制御用高保磁力膜を例えば実施例３４でのバイアス膜として用いた場合について説明する。
【０３２２】
本実施例では、図８２に示すように、配向制御用高保磁力膜１４２上に磁気的絶縁層１４６を介してスピンバルブ構造の磁気抵抗効果素子を形成した。このように、配向制御高保磁力膜１４２を用いることによって、膜端部において高保磁力膜１４２とＮｉＦｅ膜１４４が静磁結合し、バルクハウゼンノイズの原因となっているＮｉＦｅ膜端部の磁壁を固着させることができる。さらに、配向制御高保磁力膜を用いているため、高保磁力膜のＮｉＦｅ膜に対する影響、例えば膜内部の漏れ磁界等を回避でき、ＮｉＦｅ膜の軟磁気特性を劣化させることなく、良好な素子を作製できる。また、ここではスピンバルブ構造の交換バイアス膜として反強磁性膜等を用いてもよい。
【０３２３】
【発明の効果】
以上説明した如く本発明の磁気抵抗効果素子は、高い抵抗変化率および優れた軟磁気特性を同時に発揮できるものであり、その工業的価値は大なるものがある。
【図面の簡単な説明】
【図１】本発明の第１の発明の磁気抵抗効果素子（スピンバルブ構造）を示す断面図。
【図２】図１に示す磁気抵抗効果素子の抵抗変化率の外部磁界依存性を示すグラフ。
【図３】（Ａ），（Ｂ）は図１に示す磁気抵抗効果素子の磁化曲線を示すグラフ。
【図４】本発明の第１の発明の磁気抵抗効果素子（人工格子膜）の一例を示す断面図。
【図５】図４に示す磁気抵抗効果素子の抵抗変化率の外部磁界依存性を示すグラフ。
【図６】Ｃｏ₉₀Ｆｅ₁₀膜のＣｕ下地膜がある場合の保磁力の膜厚依存性を示すグラフ。
【図７】Ｃｏ₉₀Ｆｅ₁₀膜のＣｕ下地膜がない場合の保磁力の膜厚依存性を示すグラフ。
【図８】本発明の第１の発明の磁気抵抗効果素子（スピンバルブ構造）を示す断面図。
【図９】（Ａ）はサファイア基板Ｃ面におけるθ−２θスキャンＸ線回折曲線、（Ｂ）はサファイア基板Ｒ面におけるθ−２θスキャンＸ線回折曲線。
【図１０】Ｃｏ₉₀Ｆｅ₁₀膜／Ｃｕ膜／サファイア基板Ｃ面における最密面ピークに関するロッキングカーブ。
【図１１】Ｃｏ₉₀Ｆｅ₁₀膜における保磁力の最密面反射でのロッキングカーブ半値幅依存性を示すグラフ。
【図１２】（Ｃｏ₉₀Ｆｅ₁₀）_1-x Ａｌ_x 膜／Ｃｕ膜における保磁力のＡｌ濃度ｘ依存性を示すグラフ。
【図１３】Ｃｏ₉₀Ｆｅ₁₀膜／Ｃｕ膜における保磁力の最密面反射強度依存性を示すグラフ。
【図１４】（Ｃｏ₉₀Ｆｅ₁₀）_1-x Ｔａ_x 膜／Ｃｕ膜における保磁力のＴａ濃度ｘ依存性を示すグラフ。
【図１５】本発明の第１の発明の磁気抵抗効果素子（スピンバルブ構造）を示す断面図。
【図１６】本発明の第３の発明の磁気抵抗効果素子を示す断面図。
【図１７】図１６に示す磁気抵抗効果素子の容易軸方向のＭ−Ｈカーブ。
【図１８】図１６に示す磁気抵抗効果素子の困難軸方向のＭ−Ｈカーブ。
【図１９】図１６に示す磁気抵抗効果素子のＲ−Ｈカーブ。
【図２０】高抵抗アモルファス層を設けない磁気抵抗効果素子の容易軸方向のＭ−Ｈカーブ。
【図２１】高抵抗アモルファス層を設けない磁気抵抗効果素子の困難軸方向のＭ−Ｈカーブ。
【図２２】本発明の第３の発明の磁気抵抗効果素子を示す断面図。
【図２３】（Ａ）〜（Ｃ）は本発明の第３の発明の磁気抵抗効果素子の他の例の製造過程を示す断面図。
【図２４】本発明の第３の発明の磁気抵抗効果素子の他の例を示す斜視図。
【図２５】本発明の第４の発明の磁気抵抗効果素子の例を示す断面図。
【図２６】図２５に示す磁気抵抗効果素子において△ρ／ρ₀ とｄ_CoFeとの関係を示すグラフ。
【図２７】本発明の第５の発明の磁気抵抗効果素子を示す断面図。
【図２８】本発明の第５の発明の磁気抵抗効果素子を示す断面図。
【図２９】本発明の第６の発明の磁気抵抗効果素子における保磁力の強磁性膜の膜厚依存性を示すグラフ。
【図３０】本発明の第６の発明の磁気抵抗効果素子における保磁力の強磁性膜の膜厚依存性を示すグラフ。
【図３１】本発明の第６の発明の磁気抵抗効果素子の強磁性膜の磁化曲線。
【図３２】本発明の第７の発明の磁気抵抗効果素子における積層周期依存性を示すグラフ。
【図３３】本発明の第６の発明の磁気抵抗効果素子の強磁性膜における飽和磁界ＨｓとＣｕ膜厚との関係を示すグラフ。
【図３４】本発明の第７の発明の磁気抵抗効果素子の強磁性膜の磁化曲線。
【図３５】本発明の第７の発明の磁気抵抗効果素子を示す断面図。
【図３６】第７の発明において、ＣｕとＣｏＦｅとの界面状態を示す断面図。
【図３７】図３５に示す磁気抵抗効果素子の磁化曲線。
【図３８】図３５に示す磁気抵抗効果素子の抵抗変化特性を示すグラフ。
【図３９】従来の磁気抵抗効果素子の磁化曲線。
【図４０】従来の磁気抵抗効果素子の抵抗変化特性を示すグラフ。
【図４１】（Ａ），（Ｂ）は本発明の第７の発明の磁気抵抗効果素子のＣｕ下地膜を有する強磁性膜についての磁化曲線。
【図４２】本発明の第７の発明の磁気抵抗効果素子のＣｕ下地膜を有する強磁性膜についての抵抗変化特性を示すグラフ。
【図４３】本発明の第４の発明の磁気抵抗効果素子を示す断面図。
【図４４】図４３に示す磁気抵抗効果素子の磁化曲線。
【図４５】図４３に示す磁気抵抗効果素子の抵抗変化特性を示すグラフ。
【図４６】膜内の揺らぎを説明するための概略図。
【図４７】（Ａ）はＭｇＯ（１１０）面基板上Ｃｏ₉₀Ｆｅ₁₀／Ｃｕ人工格子膜の小角反射のＸ線回折曲線、（Ｂ）はＭｇＯ（１１０）面基板上Ｃｏ₉₀Ｆｅ₁₀／Ｃｕ人工格子膜の中角反射のＸ線回折曲線。
【図４８】（Ａ）は図４７におけるｆｃｃ（２２０）反射に関する［１１０］軸方向から測定したロッキングカーブ、（Ｂ）は図４７におけるｆｃｃ（２２０）反射に関する［１００］軸方向から測定したロッキングカーブ。
【図４９】（Ａ）は結晶配向面の揺らぎによる結晶配向面の法線の面内分布を示す概略図、（Ｂ）は抵抗変化率のセンス電流方向依存性を示す概略図。
【図５０】（Ａ）はＣｕ５．５nm／（Ｃｕ１．１nm／ＣｏＦｅ１nm）₁₆人工格子膜の外部磁界［１００］軸方向の磁化曲線、（Ｂ）はＣｕ５．５nm／（Ｃｕ１．１nm／ＣｏＦｅ１nm）₁₆人工格子膜の外部磁界［１１０］軸方向の磁化曲線。
【図５１】ＭｇＯ（１１０）面基板上におけるＣｏ₉₀Ｆｅ₁₀／Ｃｕ積層膜の抵抗変化率のバイアス電圧依存性を示すグラフ。
【図５２】ｆｃｃ相（１１１）面配向したＣｏ₉₀Ｆｅ₁₀／Ｃｕ積層膜に積層欠陥が導入された場合の概念図。
【図５３】ｆｃｃ相（１１１）面配向したＣｏ₉₀Ｆｅ₁₀／Ｃｕ積層膜に積層欠陥が導入された場合の原子配列を示す概念図。
【図５４】ｆｃｃ相（１１１）面配向したＣｏ₉₀Ｆｅ₁₀／Ｃｕ積層膜に双晶欠陥が導入された場合の原子配列を示す概念図。
【図５５】図５４に示す状態における抵抗変化率のセンス電流方向依存性を示す概略図。
【図５６】ガラス基板上におけるＣｏ₉₀Ｆｅ₁₀／Ｃｕ人工格子膜の抵抗変化率の基板バイアス依存性を示すグラフ。
【図５７】ガラス基板上におけるＣｏ₉₀Ｆｅ₁₀／Ｃｕ人工格子膜の長周期構造反射強度のバイアス依存性を示すグラフ。
【図５８】ガラス基板上におけるＣｏ₉₀Ｆｅ₁₀／Ｃｕ人工格子膜のｆｃｃ相（１１１）面反射強度のバイアス依存性を示すグラフ。
【図５９】ガラス基板上におけるＣｏ₉₀Ｆｅ₁₀／Ｃｕ人工格子膜の保磁力のバイアス依存性を示すグラフ。
【図６０】本発明の第８の発明の磁気抵抗効果素子を示す斜視図。
【図６１】本発明の第８の発明の磁気抵抗効果素子を示す斜視図。
【図６２】本発明の第８の発明の磁気抵抗効果素子を示す斜視図。
【図６３】本発明の第８の発明の磁気抵抗効果素子を示す斜視図。
【図６４】本発明の第８の発明の磁気抵抗効果素子を示す斜視図。
【図６５】本発明の第８の発明の磁気抵抗効果素子を示す斜視図。
【図６６】本発明の第８の発明の磁気抵抗効果素子の抵抗変化特性を示すグラフ。
【図６７】本発明の第１２の発明の磁気抵抗効果素子を示す斜視図。
【図６８】本発明の第１２の発明の磁気抵抗効果素子を示す斜視図。
【図６９】本発明の第１０の発明の磁気抵抗効果素子を示す斜視図。
【図７０】（Ａ）〜（Ｃ）は本発明の第１０の発明の磁気抵抗効果素子を示す斜視図。
【図７１】本発明の第１０の発明の磁気抵抗効果素子を示す斜視図。
【図７２】本発明の第１０の発明の磁気抵抗効果素子の積層膜の抵抗変化特性を示すグラフ。
【図７３】本発明の第１２の発明の磁気抵抗効果素子を示す斜視図。
【図７４】本発明の第１２の発明の磁気抵抗効果素子を示す断面図。
【図７５】本発明の第１３の発明の磁気抵抗効果素子を示す断面図。
【図７６】Ｃｏ／Ｃｒ積層膜のＸ線回折パターン。
【図７７】基板温度約１００℃で成膜した本発明の第１３の発明の積層膜のＲ−Ｈカーブ。
【図７８】基板温度約２００℃で成膜した本発明の第１３の発明の積層膜のＲ−Ｈカーブ。
【図７９】パターン幅方向を容易軸とした場合の本発明の第１３の発明の積層膜のＲ−Ｈカーブ。
【図８０】下地膜を設けない場合の本発明の第１３の発明の積層膜のＲ−Ｈカーブ。
【図８１】本発明の第１３の発明の磁気抵抗効果素子を示す断面図。
【図８２】本発明の第１３の発明の磁気抵抗効果素子を示す断面図。
【図８３】従来の磁気抵抗効果素子を示す斜視図。
【図８４】従来の磁気抵抗効果素子のＲ−Ｈカーブ。
【符号の説明】
１０，２０…サファイア基板、１１，２１，７１…Ｃｏ₉₀Ｆｅ₁₀膜、１２，２２，２３，７０…Ｃｕ膜、１３…ＦｅＭｎ膜、１４…Ｔｉ膜、１５，２４…Ｃｕリード、２６…Ｎｉ酸化物膜、３０，４１，１４０…支持基板、３１，４６…高抵抗アモルファス層、３２，４４，８３，８５，９１，９３，１０３，１０５，１０７，１１２，１１４，１１６，１１８，１２１，１２３，１３２，１３４，１３６，１４４…強磁性膜、３３，４５，１４３…中間層、３４…交換バイアス層、３５，４７…リード、４２…ＣｏＰｔＣｒ膜、４３…レジスト、５０，８０，９０，１００，１２０，１３０…基板、５１…強磁性積層単位、５２，８４，８７，８８，９２，１０４，１０６，１１３，１１５，１１７，１２２，１３３，１３５，１６３…非磁性膜、５３，８２，９４，１０２，１０８，１１１，１１９，１２４，１３１，１３７，１６５…反強磁性膜、５４，１６６…保護膜、５５，６２，８６，９６，１０９，１２５，１４５…電極端子、６０…ＭｇＯ基板、６１…積層膜、８１，１０１，１４１…下地膜、９５…硬質磁性膜、９７…絶縁膜、１４２…高保磁力膜、１４６…磁気的絶縁層、１６０…熱酸化Ｓｉ基板、１６１…高抵抗強磁性膜、１６２…第１の強磁性膜、１６４…第２の強磁性膜、１６７ａ，１６７ｂ…電極、１６９…高抵抗反強磁性膜。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetoresistive effect element used for a magnetic head or the like.
[0002]
[Prior art]
When reading information recorded on a magnetic recording medium, the voltage induced in the coil by electromagnetic induction generated at that time is moved relative to the recording medium when the magnetic head for reading with the coil is moved. The method of detecting is common. It is also known to use a magnetoresistive head for reading information [IEEE MAG-7, 150 (1971)]. This magnetoresistive head utilizes the phenomenon that the electrical resistance of a certain type of ferromagnet changes according to the strength of the external magnetic field, and is known as a high sensitivity head for magnetic recording media. . In recent years, the magnetic recording medium has been reduced in size and capacity, and the relative speed between the magnetic head for reading and the magnetic recording medium at the time of reading information has been reduced. Therefore, a large output can be obtained even at a low relative speed. There is an increasing expectation for a magnetoresistive head that can be removed.
[0003]
Conventionally, a NiFe alloy (hereinafter abbreviated as permalloy) is used in a portion where resistance is changed by sensing an external magnetic field in a magnetoresistive head (hereinafter referred to as an MR element). Permalloy has a magnetoresistance change rate of up to about 3% even if it has good soft magnetic properties, and when used in MR elements for miniaturized and large capacity magnetic recording media, the magnetoresistance change rate is low. Insufficient. For this reason, what shows a more sensitive magnetoresistive change as an MR element material is desired.
[0004]
In recent years, multilayer films formed by alternately laminating ferromagnetic films and non-magnetic films under certain conditions, such as Fe / Cr and Co / Cu, so-called artificial lattice films, have an anti-strength between adjacent ferromagnetic films. It has been confirmed that a giant magnetoresistance change appears by using magnetic coupling, and a large magnetoresistance change rate exceeding 100% has been reported [Phys. Rev. Lett., Vol. 61, 2472 (1988)] [Phys. Rev. Lett., Vol. 64, 2304 (1990)].
[0005]
On the other hand, even when the ferromagnetic film is not antiferromagnetically coupled, an exchange bias is applied to one of the two ferromagnetic films sandwiching the nonmagnetic film by another means without using antiferromagnetic coupling between adjacent ferromagnetic films. It has also been reported that the magnetization of the other ferromagnetic film is reversed and the magnetization of the other ferromagnetic film is reversed by an external magnetic field, creating an antiparallel state across the nonmagnetic film and realizing a large magnetoresistance change. ing. This type is referred to herein as a spin valve structure [Phys. Rev. B., Vol. 45806 (1992)] [J. Appl. Phys., Vol. 69, 4774 (1991)].
[0006]
Both the artificial lattice film and the spin valve structure film have considerably different resistance change characteristics and magnetic characteristics of the laminated film depending on the type of the ferromagnetic film. For example, when Co is used in the spin valve structure, for example, Co / Cu / Co / FeMn produces a large resistance change rate of 8%, but the coercive force is as high as about 20 Oersted and the soft magnetic characteristics are not good. On the other hand, when permalloy is used, for example, NiFe / Cu / NiFe / FeMn has reported a good value with a coercive force of 1 Oersted or less, but the resistance change rate is not as large as about 4% [J. Al. Phys., Vol. 69, 4774 (1991)]. As described above, the soft magnetic characteristics of the laminated film are good, but the resistance change rate is lowered. Therefore, the constituent elements and the film structure of the laminated film satisfying both the soft magnetic characteristics and the resistance change rate have not been reported yet.
[0007]
The two types of films have the following problems.
[0008]
In the artificial lattice film, the resistance change rate ΔR / R ignoring the magnetic field range is larger than that of the spin valve type, but since the antiferromagnetic coupling is large, the saturation magnetic field Hs is large and soft magnetism is difficult. Since antiferromagnetic coupling is sensitive to the interface structure, stable film formation is difficult, and changes with time are likely to occur.
[0009]
With a spin valve structure film, good soft magnetic characteristics can be obtained when a NiFe film is used as the ferromagnetic film, but ΔR / R is smaller than that of the artificial lattice film because there are two interfaces between the ferromagnetic film and the nonmagnetic film. . In order to increase the number of interfaces, even if a multilayer film is formed by repeatedly laminating a ferromagnetic film, non-magnetic film, and antiferromagnetic film, an antiferromagnetic film with high resistance exists in the laminated film. As a result, spin-dependent scattering is suppressed, and eventually an increase in ΔR / R cannot be expected.
[0010]
In addition, when a signal magnetic field is applied in the direction of the hard axis of a ferromagnetic film suitable for a magnetic head, the magnetization is rotated by the ferromagnetic film on only one side, and therefore, as shown in FIG. The angle formed by the magnetizations of the ferromagnetic film 2 and the ferromagnetic film 4 on the nonmagnetic film 3 can be changed only to about 90 °. Note that an angle change of up to 180 ° occurs in the easy axis direction. As a result, ΔR / R decreases to about half of the easy axis direction. Here, even if the exchange bias magnetic field of the ferromagnetic film 2 on the antiferromagnetic film 1 is weakened by some method so that the magnetization rotation of both the ferromagnetic films 2 and 4 can be used, the nonmagnetic film 3 When the film thickness is reduced and the resistance change rate is increased, ferromagnetic coupling works between the two ferromagnetic films, so that the magnetization between the ferromagnetic films is directed in the same direction in the state of the signal magnetic field 0. As a result, even if the magnetization is rotated by the signal magnetic field, the change in the angle of magnetization between the two ferromagnetic films becomes slight and the resistance change becomes small.
[0011]
Furthermore, the ferromagnetic coupling between the two ferromagnetic films that works when the film thickness of the nonmagnetic film is reduced also causes a problem that the magnetic permeability of the ferromagnetic film is deteriorated. In addition, a NiFe film having a good soft magnetic property has a normal anisotropic magnetoresistive effect. However, in a system in which a sense current is passed in a direction perpendicular to the signal magnetic field, as shown in FIG. When the magnetizations of the two ferromagnetic films are aligned in the same direction, the anisotropic magnetoresistance effect due to the signal magnetic field and the resistance change due to spin-dependent scattering cancel each other.
[0012]
[Problems to be solved by the invention]
First, in order to obtain high sensitivity in the magnetic head, it is necessary to increase the supplied current as much as possible. However, in this case, both films have a common problem with the artificial lattice film and the spin valve structure film. The magnetization direction of some ferromagnetic films is disturbed by the magnetic field generated by this current, and a highly sensitive resistance change against the magnetic field is prevented. Specifically, in the vicinity of the uppermost layer and the lowermost layer of the laminated film, the current magnetic field is strong, and the magnetization tends to be directed in the direction of the current magnetic field.
[0013]
Secondly, there are important problems to be solved in applying to magnetic heads such as Barkhausen noise suppression and operating point bias.
[0014]
As described above, the magnetoresistive effect element having an artificial lattice film or spin valve structure film using spin-dependent scattering exhibits good soft magnetic characteristics even when a large current is applied, which is indispensable for high sensitivity, and is large. At present, the resistance change rate ΔR / R cannot be shown.
[0015]
The present invention has been made in view of the above points, and has an application to a highly sensitive magnetic head having a spin valve structure film or an artificial lattice film having good soft magnetic characteristics and sufficient resistance change rate ΔR / R. An object of the present invention is to provide a magnetoresistive effect element capable of performing
[0016]
[Means for Solving the Problems]
The present invention made to achieve the above object relates to a magnetoresistive element having a spin valve structure film as shown in FIG. 1 or an artificial lattice film as shown in FIG. It has a basic structure in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated. Here, as the material of the ferromagnetic film, unless otherwise specified, Co, CoFe, CoNi, NiFe, Sendust, NiFeCo, Fe ₈ N etc. can be mentioned. In addition, Co _100-x Fe _x A ferromagnetic film made of (0 <x ≦ 40 atomic%) is preferable because it exhibits high ΔR / R and low Hc. The film thickness of the ferromagnetic film is preferably 1 to 20 nm. In the present invention, ferromagnetism means including ferrimagnetism. In addition, as the material of the nonmagnetic film, Mn, Fe, Ni, Cu, Al, Pd, Pt, Rh, Ru, Ir, Au, Ag, or other nonmagnetic metal, CuPd, CuPt, CuAu, CuNi alloy, etc. Can be mentioned. The film thickness of the nonmagnetic film is preferably 0.5 to 20 nm, and particularly preferably 0.8 to 5 nm.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The magnetoresistive effect element of the present invention will be specifically described below.
[0018]
The first invention of the present invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate. The film is non-bonded, and at least one of the ferromagnetic films is mainly composed of at least one element selected from the group consisting of Co, Fe, and Ni, and its closest surface is oriented in the direction perpendicular to the film surface A magnetoresistive effect element is provided.
[0019]
In the first invention, the two ferromagnetic films being non-coupled means that there is substantially no antiferromagnetic exchange coupling between the two ferromagnetic films. Therefore, when realizing an antiparallel magnetization arrangement state in two ferromagnetic films, means different from antiferromagnetic coupling between the ferromagnetic films is formed as means for applying a bias magnetic field to the ferromagnetic film. . The close-packed plane orientation means the (111) plane in the fcc phase and the (001) plane in the hcp phase.
[0020]
In the first invention, as a method of orienting the close-packed surface of the ferromagnetic film in the direction perpendicular to the film surface, the material of the ferromagnetic film is Pd, Al, Cu, Ta, In, B, Nb, Hf, Mo. , W, Re, Ru, Rh, Ga, Zr, Ir, Au, and Ag, and a method of adding at least one element selected from the group consisting of Ag (particularly Pd, Cu, Au, Ag are preferably added), a method using a C surface of a sapphire substrate as a substrate for forming a ferromagnetic film, Cu, Ni, CuNi, NiFe, Ge, Si, GaAs, etc. between the substrate and the ferromagnetic film A base film made of a material selected from the group consisting of a material having an fcc lattice, a material having a rhombohedral lattice such as NiO, Ti, a magnetic amorphous metal (CoZrNb, CoHfTa, etc.), and a nonmagnetic amorphous material Provided Method, and a method for forming, and the like by ultra-high vacuum deposition apparatus MBE or the like.
[0021]
Here, a specific example of the base film will be described in detail. For example, in a Co-based ferromagnetic film, Co ₉₀ Fe _Ten In the case of using a ferromagnetic film having an fcc lattice typified by a film, Cu-Ge-Zr, Cu-P, Cu-P-Pd, Cu-Pd-Si, Cu-Si-Zr, Cu-Ti, Cu-based alloys typified by Cu-Sn, Cu-Ti-Zr, etc., Au-based alloys typified by Au-Dy, Au-Pb-Sb, Au-Pd-Si, Au-Yb, etc., Al-Cr, Al-based alloys typified by Al-Dy, Al-Ga-Mg, Al-Si, etc., Pt-based alloys, Pd-based alloys typified by Pd-Si, Pd-Zr, etc., Be-Ti, Be-Ti- Be-based alloys such as Zr, Be-Zr, Ge-based alloys represented by Ge-Nb, Ge-Pd-Se, Ag-based alloys, Rh-based alloys, Mn-based alloys, Ir-based alloys, Pb-based alloys, etc. Metal system having fcc lattice, or metal having these fcc lattices as main component A material having a fcc lattice, such as an alloy system, a material having a diamond structure such as Ge, Si, and diamond, a material having a zinc blende type structure such as GaAs, Ga—Al—As, Ga—P, and In—P The material which has as a main component at least 1 type chosen from these, or the material which added other elements to them, etc. can be used. Among the materials described above, substances other than single element metals already have a sufficiently high specific resistance as compared with the ferromagnetic film, and thus have the effect of suppressing the current for shunt shunting. In addition, there are various combinations of increases in specific resistance due to addition of other elements to a single element metal, but Cu-based alloys such as Cu-Ni, Cu-Cr, Cu-Zr, Au-Cr, Alloys such as Fe—Mn, Pt—Mn, and Ni—Mn are examples.
[0022]
Nonmagnetic amorphous materials include nonmagnetic single element metals and alloys, nonmagnetic metal materials such as those containing nonmetals as additives, amorphous Si such as hydrogenated Si, hydrogenated carbon, Nonmagnetic nonmetallic materials such as amorphous carbon such as glassy carbon and graphitic carbon can be used.
[0023]
The thickness of the base film as described above is not particularly limited, but is preferably 100 nm or less. This is because not only the effect is not obtained even if the film thickness of the base film is made too thick, but conversely, the ratio of the current flowing through the base film in the entire element is large, and as a result, the rate of change in resistance is small. is there. In the first invention, the base film improves the close-packed plane orientation of the ferromagnetic film. Furthermore, among the materials described above, non-magnetic amorphous materials can be grown in a layered manner regardless of the substrate material, and a stable and smooth surface can be obtained. In addition to improving the (111) orientation, Thus, the surface smoothness of the ferromagnetic film formed thereon and the smoothness of the interface with the nonmagnetic film can be improved. Accordingly, it is possible to stably obtain a good resistance change rate. Further, when a nonmagnetic material is used as the base film in the first invention, the ferromagnetic film formed thereon is not adversely affected.
[0024]
When the base film is formed, the crystal orientation is improved, but the smoothness is deteriorated and the resistance change rate may be lowered. Therefore, when a material having an fcc lattice or a magnetic amorphous metal is used as the material of the first base film for promoting close-packed surface orientation, Ti, Ta, Zr, or a nonmagnetic amorphous material is used. It is preferable that the second base film for improving the smoothness made of, for example, has a two-layer structure disposed between the first base film and the substrate. By adopting such a configuration, it is possible to obtain a magnetoresistive effect element having both good soft magnetic characteristics obtained by improving the close-packed plane crystal orientation and a high magnetoresistance change rate. Further, in the two-layer structure, in addition to the above-described effect, the inside of the element can be obtained by using the second base film made of a material having the same crystal system as the ferromagnetic film and having a specific resistance larger than that of the ferromagnetic film material. It is possible to reduce the shunt current component in the current flowing through the. When the base film is used as a laminated structure of two or more layers, it is desirable that the thickness of the laminated structure does not exceed 100 nm.
[0025]
As the above-described method for forming the base film, a bipolar sputtering method using high frequency discharge of 13.56 MHz or 100 MHz or more, and an ion beam sputtering method using various ion sources such as an ECR ion source and a Kaufman type ion source. Various film forming methods such as vacuum deposition using an electron beam evaporation source or Knudsen cell, thermal CVD, CVD using various plasmas, MOCVD using organic metal as a raw material, and MOMBE can be applied. it can. As common to these film forming methods, it is important to manage water and oxygen through evacuation to ultra-high vacuum and ultra-high purity of source gas. More specifically, H ₂ O and O ₂ The content of is preferably reduced to ppm or less, desirably to the ppb order.
[0026]
In the first invention, it is preferable to use a Co-based alloy as the material of the ferromagnetic film. The reason for this is that, in the system not containing Co, the resistivity change ΔR / R of the obtained magnetoresistive effect element is about 4%, which is lower than that in the case of the Co-based alloy. This is because even if the orientation is realized, Co has a large magnetocrystalline anisotropy, so that the soft magnetic characteristics may not be improved so much. At this time, in particular, Co _100-x Fe _x (5 ≦ x ≦ 40 atomic%) is preferable because it has a high ΔR / R of 10% or more and a low Hc of less than 80 A / m by adopting the fcc phase (111) orientation.
[0027]
As for the crystal orientation of the ferromagnetic film, the full width at half maximum of the rocking curve of the close-packed surface (for example, fcc phase (111) surface) reflection peak in the X-ray diffraction curve is preferably less than 20 °, particularly preferably 7 ° or less.
[0028]
In the first invention, the additive element content is within a range in which the ferromagnetism of a ferromagnetic film mainly composed of a CoFe alloy or the like is not impaired at room temperature and an intermetallic compound that inhibits spin-dependent scattering is not generated. There must be. For example, when the additive element is Al, Ga, or In, the content is preferably less than 6.5 at%. When the additive element is Nb, Ta, Zr, Hf, B, Mo, or W, the content is preferably less than 10 at%. When the additive element is Cu, Pd, Au, Ag, Re, Ru, Rh, or Ir, the content is preferably less than 40 at%.
[0029]
Moreover, as a substrate material, MgO, sapphire, diamond, graphite, silicon, germanium, SiC, BN, SiN, AlN, BeO, GaAs, GaInP, GaAlAs, BP, and the like, and their polycrystals Typical examples include bodies, sintered bodies containing them, magnetic or nonmagnetic metal single crystals, polycrystals, sintered bodies, etc., depending on the type of ferromagnetic film and the underlying film material. The substrate material is selected. In particular, it is preferable to use the C-plane of a sapphire substrate that has good lattice matching with a Co-based alloy and has a characteristic that a smooth surface can be easily obtained. When a single crystal substrate such as a sapphire substrate is used, the thickness of the ferromagnetic film is preferably 20 nm or less. This is because the close-packed plane orientation deteriorates when the thickness of the ferromagnetic film exceeds 20 nm.
[0030]
Here, in the magnetic film oriented in the close-packed plane, Hc increases rapidly when the magnetization direction is slightly tilted from the close-packed plane. Therefore, if the substrate surface is wavy, the magnetization direction may deviate from the (111) plane even if the close-packed surface orientation is realized, so that Hc may not be lowered. For this reason, the surface roughness of the substrate is preferably less than 5 nm.
[0031]
The magnetoresistive effect element according to the first aspect of the invention may be one in which a nonmagnetic film and a ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration.
[0032]
In the first invention, the most dense surface of the ferromagnetic film containing at least one element selected from the group consisting of Co, Fe, and Ni as a main component, for example, the fcc phase (111) surface is perpendicular to the film surface. Good soft magnetic characteristics can be obtained by orientation. This is because the magnetocrystalline anisotropy K is in the fcc phase (111) plane. ₁ This is because the easy magnetization axis depending on the value does not appear. In addition, by controlling the surface roughness of the substrate on which the ferromagnetic film is formed, the magnetization in the ferromagnetic film can be preserved in the close-packed plane, thereby reducing the coercive force associated with crystalline magnetic anisotropy. Can be made. Therefore, better soft magnetic characteristics can be obtained. Also, by aligning the rocking curve half-width to less than 20 °, desirably 7 ° or less, good soft magnetic properties with a coercive force (Hc) of up to 100 A / m, non-oriented films and other orientations A highly sensitive magnetoresistive element having both a high resistance change rate (ΔR / R) (for example, ΔR / R to 10% for a CoFe film) exceeding (for example, fcc phase (100) orientation) and a high magnetic permeability. Can be obtained.
[0033]
Here, the normal of the main crystal orientation plane of the laminated film has a component in the film plane due to fluctuations in the crystal orientation plane, and this in-plane component has anisotropy or is a crystalline laminate. A normal of a surface defect generated in the film has a fluctuation in the film surface, and this fluctuation may have anisotropy in the film surface. Such a direction with strong anisotropy is a direction in which ferromagnetic atoms and nonmagnetic atoms are likely to be mixed in the atomic plane on which the film grows. Therefore, it is considered that the probability that electrons are spin-dependently scattered at the interface is increased by flowing the sense current in this direction, that is, in the direction in which the anisotropy due to the in-film component becomes the largest.
[0034]
That is, when the crystal orientation plane of the ferromagnetic film of the laminated film Note is fluctuated or the atomic arrangement is disturbed due to the introduction of surface defects, the disorder of the atomic arrangement in the crystal orientation plane is large. By passing a sense current in the direction, electrons pass equivalently through many interfaces and ferromagnetic films, and the probability of spin-dependent scattering increases. Thus, by setting the direction of the sense current to a direction along the fluctuation direction of the crystal orientation plane of the laminated film, the magnetoresistive effect element exhibits a larger resistance change rate.
[0035]
A second invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate, wherein at least one of the ferromagnetic films is Co , Fe, and Ni as main components, Pd, Al, Cu, Ta, In, B, Nb, Hf, Mo, W, Re, Ru, Rh, Ga, Provided is a magnetoresistive element having a composition in which at least one element selected from the group consisting of Zr, Ir, Au, and Ag is added and contained.
[0036]
The magnetoresistive effect element according to the second invention may be one in which a nonmagnetic film and a ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration.
[0037]
In the second invention, the additive element content is within a range in which the ferromagnetic property of a ferromagnetic film mainly composed of a CoFe alloy or the like is not impaired at room temperature and an intermetallic compound that inhibits spin-dependent scattering is not generated. There must be. For example, when the additive element is Al, Ga, or In, the content is preferably less than 6.5 at%. When the additive element is Nb, Ta, Zr, Hf, B, Mo, or W, the content is preferably less than 10 at%. When the additive element is Cu, Pd, Au, Ag, Re, Ru, Rh, or Ir, the content is preferably less than 40 at%.
[0038]
In the second invention, by adding an additive element as described above, a high-sensitivity magnetoresistive element having good soft magnetic characteristics with Hc of up to 100 A / m and ΔR / R of 5% or more is obtained. Can be obtained. In particular, the addition of Al, Ta, Zr, Nb, and Hf significantly improves the soft magnetic characteristics. In this case, the reason why the soft magnetic characteristics are improved is not clear at present, but it is considered that the effect of reducing the crystal magnetic anisotropy is included in addition to the improvement of the crystal orientation. Further, even if Pd, Cu, Ag, and Au are added and contained in a large amount up to about 40 at%, an intermetallic compound is not generated, and the lattice constant increases, so that it can be compared with an intermediate nonmagnetic film such as Cu. Lattice matching is improved, and an increase in spin-dependent scattering due to so-called bulk scattering can be expected. For this reason, high ΔR / R can be maintained in addition to the improvement of the soft magnetic characteristics.
[0039]
According to a third aspect of the present invention, there is provided a laminated film in which (n + 1) layers of ferromagnetic films and n layers of nonmagnetic films are alternately formed on a substrate (where n represents an integer of 1 to 4). The magnetoresistive element is characterized in that a ferromagnetic film having a resistivity of 50 μΩcm or more is further laminated adjacent to at least one of the uppermost layer and the lowermost ferromagnetic film of the laminated film. A magnetoresistive element is provided.
[0040]
In the third invention, the high resistance ferromagnetic film having a resistivity of 50 μΩcm or more may be either a ferromagnetic film or a ferrimagnetic film. In addition, the reason why the ferromagnetic film is a laminated film having five or less layers is that when the number of interfaces of the ferromagnetic film / nonmagnetic film increases, the function of the interface of the high resistance ferromagnetic film / ferromagnetic film becomes relative. This is because ΔR / R does not improve due to a decrease. Therefore, the third invention is suitable for the magnetoresistive effect having a spin valve structure film.
[0041]
Thus, by stacking the ferromagnetic film so that the high-resistance ferromagnetic film is in contact with the ferromagnetic film, generation of magnon at the interface can be suppressed. As a result, it is possible to reduce the probability of electron spin reversal due to collision between magnons and electrons, thereby increasing the rate of resistance change at room temperature, and realizing a highly sensitive magnetoresistive element. . However, if the resistivity of the high resistance ferromagnetic film material is less than 50 μΩcm, the current flows mainly in the high resistance ferromagnetic film, and conversely the resistance change rate decreases. In other words, by using a ferromagnetic film having a resistivity of 50 μΩcm or more, it is possible to prevent a current from being taken by the high-resistance ferromagnetic film, and a decrease in the magnetoresistance change rate due to the shunt effect can be suppressed.
[0042]
As a material of the high resistance magnetic film, elements such as Ti, V, Cr, Mn, Zn, Nb, Tc, Hf, Ta, W, and Re are added to Ni, Fe, Co, NiFe, NiFeCo, CoFe, Co alloy and the like. Additions can be mentioned.
[0043]
In the third invention, the high resistance ferromagnetic film is preferably a high resistance soft magnetic film. At this time, by integrating the adjacent ferromagnetic film and the high resistance soft magnetic film, the magnetization of the ferromagnetic film is increased along with the magnetization rotation of the high resistance soft magnetic film, for example, an amorphous film having good soft magnetic characteristics. Similarly, the magnetization is rotated. This improves the soft magnetic properties of the ferromagnetic film.
[0044]
As the high resistance soft magnetic film, a high resistance amorphous film made of CoZrNb or the like, a microcrystalline high resistance soft magnetic film made of FeZrN, CoZrN, or the like, or NiFeX, where X is Rh, Nb, Zr, Hf, Ta, Re , Ir, Pd, Pt, Cu, Mo, Mn, W, Ti, Cr, Au, and a film made of a material that is any one element selected from the group consisting of Ag can be used. Of these, when an amorphous film or a film made of a material having an fcc phase made of CoZrN, NiFeNb or the like is formed adjacent to the lowermost ferromagnetic film, the fcc (111) orientation of the ferromagnetic film thereon is increased. This is preferred because it is promoted.
[0045]
The film thickness of the high resistance ferromagnetic film is preferably 0.5 nm or more. This is because if the film thickness is less than 0.5 nm, the magnetic resistance of the high-resistance ferromagnetic film itself becomes weak and it is difficult to suppress the generation of magnon. On the other hand, when the soft magnetic property of the high resistance ferromagnetic film is inferior to the soft magnetic property of the ferromagnetic film adjacent thereto, the thickness of the high resistance ferromagnetic film is desirably 10 nm or less. This is because if the film thickness exceeds 10 nm, the magnetization process of the ferromagnetic film is affected, making it difficult to obtain soft magnetic characteristics.
[0046]
The fourth invention is a laminated film in which (n + 1) layers of ferromagnetic films and n layers of first nonmagnetic films are alternately formed on a substrate (where n represents an integer of 1 to 4). The thickness of at least one of the uppermost layer and the lowermost ferromagnetic film of the laminated film is 5 nm or less, and is adjacent to the ferromagnetic film having a thickness of 5 nm or less. And providing a magnetoresistive effect element in which a second nonmagnetic film having a resistivity equal to or less than twice that of the ferromagnetic film is further laminated.
[0047]
In the fourth invention, the material of the second nonmagnetic film preferably has the same crystal structure as the material of the adjacent ferromagnetic film. That is, when the ferromagnetic film is made of a material having an fcc phase, a material having an fcc phase is also preferably used for the first nonmagnetic film. At this time, the difference in lattice constant between the material of the second nonmagnetic film and the material of the ferromagnetic film is preferably within 5%. In particular, when the second nonmagnetic film is formed adjacent to the lowermost ferromagnetic film, the ferromagnetic film is epitaxially grown by improving the crystal matching between the ferromagnetic film and the second nonmagnetic film. Therefore, scattering of electrons at the interface can be suppressed.
[0048]
Specifically, as the material of the second nonmagnetic film, at least one element selected from the group consisting of Mn, Fe, Ni, Cu, Al, Pd, Pt, Rh, Ir, Au, and Ag is used. The main component can be used. Further, a base film may be interposed between the substrate and the second nonmagnetic film.
[0049]
In the fourth invention, the crystal of the material constituting the ferromagnetic film preferably has a large crystal grain size in the film thickness direction so that crystal growth is not inhibited in each ferromagnetic film. If the number of ferromagnetic films exceeds five, the number of interfaces between the ferromagnetic film and the nonmagnetic film increases and the spin-dependent scattering effect may be substantially lost. Is 5 layers or less.
[0050]
In the fourth invention, the thickness of the second nonmagnetic film is preferably in the range of 0.2 to 20 nm. This is because if the thickness of the second nonmagnetic film is less than 0.2 nm, the probability that the electrons flowing into the second nonmagnetic film will undergo inelastic scattering at the interface with the substrate or the like increases. It becomes difficult to effectively extend the free path. Conversely, even if the film thickness exceeds 20 nm, no further effect can be obtained, and the current flowing only through the second nonmagnetic film increases, resulting in a large resistance change rate. It is because it becomes difficult to obtain.
[0051]
When the magnetoresistive effect element of the fourth invention is applied to a sensor, the material of the second nonmagnetic film needs to be a plate-like body that is twice or less of a CoFe alloy that is a material of the ferromagnetic film. Furthermore, it is preferable to have a resistivity smaller than that of the ferromagnetic film. This is because if the resistivity of the second nonmagnetic film is significantly greater than the resistivity of the ferromagnetic film, electrons flowing into the second nonmagnetic film are scattered and the effective mean free path can be kept long. This is because an increase in resistance change rate cannot be expected. Further, it is desirable that the material of the second nonmagnetic film has a resistivity equal to or higher than 1/4 of the resistivity of the ferromagnetic film. This is because when the resistivity of the second nonmagnetic film material is less than ¼ of the resistivity of the ferromagnetic film, current easily flows only through the second nonmagnetic film.
[0052]
In such a fourth invention, the second nonmagnetic film is laminated adjacent to at least one of the ferromagnetic films, so that even if the thickness of the ferromagnetic film is reduced to 5 nm or less, the effective electron can be obtained. It takes advantage of maintaining a long mean free path. For example, in a spin valve structure film, as the thickness of the ferromagnetic film is reduced, the specific resistance increases and the resistance change rate decreases. Therefore, by making the ferromagnetic film thin and simultaneously laminating the second nonmagnetic film in contact with the thinned ferromagnetic film, electrons are not subjected to inelastic scattering on the surface of the ferromagnetic film, and the second nonmagnetic film Thus, the ferromagnetic film can be made thin while keeping the effective mean free path long. At this time, in order to obtain the above effect, the number of laminated ferromagnetic films needs to be five or less.
[0053]
As described above, in the fourth invention, the second nonmagnetic film is laminated in contact with the ferromagnetic film, so that even if the thickness of the ferromagnetic film, which usually causes a significant decrease in the resistance change rate, is 5 nm or less. Thus, a magnetoresistive effect element having a large resistance change rate can be obtained. In addition, by reducing the thickness of the ferromagnetic film to 5 nm or less, even if the ferromagnetic film is processed into a fine shape corresponding to high-density magnetic recording / reproducing with a narrow track width, generation of domain walls due to a demagnetizing field can be suppressed. Thus, the detection sensitivity of the signal magnetic field is not lowered, and the generation of Barkhausen noise can be suppressed. As a result, it is possible to realize a magnetoresistive element with low noise and high sensitivity suitable for reproducing high density recording.
[0054]
Note that the magnetoresistive element of the fourth invention may have either a spin valve structure film or an artificial lattice film. However, for the spin-valve magnetoresistive element, it is preferable to form a second ferromagnetic film adjacent to a ferromagnetic film whose magnetization is not fixed by an antiferromagnetic film or the like.
[0055]
A fifth invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate, the uppermost layer and the uppermost layer of the laminated film. Provided is a magnetoresistive effect element characterized in that a thin film having a higher resistivity and a longer mean free path than that of the ferromagnetic film is further laminated adjacent to at least one of the lower ferromagnetic films.
[0056]
In the fifth invention, the material of the thin film is a semimetal such as Bi, Sb, or carbon, a semiconductor degenerated by doping at a high concentration, SnO ₂ TiO ₂ And oxide semiconductors. The thickness of the thin film is preferably in the range of 1 to 50 nm. This is because if the thickness of the thin film is less than 1 nm, the effect of increasing the mean free path of electrons cannot be sufficiently obtained, and if the thickness exceeds 50 nm, no further effect can be obtained, and only the thin film flows. This is because the current increases and it becomes difficult to obtain a large resistance change rate. Furthermore, if the resistivity of the thin film is smaller than that of the ferromagnetic film, current flows mainly through the thin film, and the magnetoresistive effect is reduced, so that the thin film has a higher resistivity than the ferromagnetic film. To have.
[0057]
In the fifth invention, the mean free path means the average distance that electrons move without being scattered by other objects.
[0058]
In the fifth invention, when the film thickness of the ferromagnetic film is in contact with the thin film, it is preferably 5 nm or less for the same reason as in the fourth invention, and the ferromagnetic film not in contact with the thin film ensures the mean free path. Therefore, the range of 2 to 20 nm is preferable.
[0059]
Such a fifth invention utilizes the fact that the effective mean free path of the entire laminated film can be increased by laminating a thin film having a long mean free path in contact with at least one of the ferromagnetic films. ing. For example, the following is known as a physical mechanism of the magnetoresistive effect in the spin valve type laminated film. That is, in a spin valve type laminated film, when the directions of magnetization between two ferromagnetic films are parallel to each other, conduction electrons having either a spin parallel to the magnetization or a spin antiparallel to the magnetization are transferred to the film. It becomes possible to have a long mean free path as a whole, and exhibits a low specific resistance as a whole. On the other hand, when the magnetization directions between the two ferromagnetic films are antiparallel to each other, conduction electrons having a long mean free path do not exist in the entire film, and the specific resistance value becomes high. The magnetoresistive effect in the spin valve type laminated film is determined by the difference in length of the mean free path in these two states.
[0060]
Furthermore, it is known that the mean free path is different between an electron having a spin parallel to the magnetization and an electron having an antiparallel spin inside the ferromagnetic film. Electrons in the spin direction having a long mean free path inside the ferromagnetic film can increase the magnetoresistive effect of the spin-valve type stacked film when having a longer mean free path. Therefore, in the fifth invention, by stacking a thin film whose mean free path is longer than that of the ferromagnetic film, it is possible to lengthen the effective mean free path of electrons and increase the magnetoresistive effect. Yes. However, if the specific resistance of the thin film is smaller than that of the ferromagnetic film, current flows mainly in the laminated thin film, and the magnetoresistive effect is reduced. Therefore, the constituent material of the thin film needs to have a resistivity equal to or higher than that of the ferromagnetic film at the same time as having a long mean free path.
[0061]
In addition, as a thin film having a long mean free path, a material having a high resistivity is used, and by reducing the thickness of the ferromagnetic film in contact therewith, the specific resistance value of the entire laminated film can be increased. . As a result, a laminated film having a high specific resistance value can be obtained, and a large signal voltage can be extracted with a low current density even in a fine pattern. Therefore, problems such as heat generation and migration can be avoided.
[0062]
The magnetoresistive effect element according to the fifth aspect of the invention may be one in which a nonmagnetic film and a ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration.
[0063]
A sixth invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate, wherein the strongest of the lowermost layer of the laminated film There is provided a magnetoresistive effect element characterized in that the magnetic film is made of a CoFe alloy, and a base film having an fcc phase having a lattice constant larger than that of the CoFe alloy is further laminated adjacent to the ferromagnetic film.
[0064]
In the sixth invention, when the ferromagnetic film formed on the base film having the fcc phase having a large lattice constant is made of a CoFe alloy, low Hc is realized. _100-x Fe _x The improvement of the soft magnetic property is remarkable for the ferromagnetic film made of (5 ≦ x ≦ 40 atomic%). This is because if the Fe concentration is less than 5 atomic%, the hcp phase is mixed, and conversely if the Fe concentration exceeds 40 atomic%, the bcc phase is mixed and lattice mismatch occurs. Other elements that can be added to CoFe include Pd, Al, Cu, Ta, In, B, Zr, Nb, Hf, Mo, Ni, W, Re, Ru, Ir, Rh, Ga, Au, and Ag. Even when these elements are added and contained, the same Hc reduction is realized.
[0065]
In the sixth invention, the base film is not limited as long as it is a material having an fcc phase and a lattice constant larger than that of CoFe. However, a material having a resistivity higher than that of the CoFr alloy constituting the ferromagnetic film is used. preferable. Specifically, Ni, an alloy containing these as a main component, or a ferromagnetic material having an fcc phase, such as Cu, Pd, or Al can be used. If the film thickness of this base film is 1 atomic layer or more, Hc can be reduced, and it is preferable to set it to 100 nm or less. However, when a material having a low resistivity such as Cu is used for the base film, the sense current is likely to be shunted to the base film, so that the film thickness is particularly preferably 2 nm or less. In addition, a film for improving smoothness is preferably formed between the substrate and the base film, and a film made of Cr, Ta, Zr, Ti or the like is used as the film for improving smoothness. Can be used.
[0066]
In the sixth aspect of the present invention, a Co film, which is a ferromagnetic film, is formed on a base film made of a material having an fcc phase and a lattice constant larger than that of the ferromagnetic film. _100-x Fe _x When a film (0 <x <100 atomic%) is formed, an appropriate lattice strain is induced in the CoFe film, and as a result, Hc is significantly reduced to exhibit good soft magnetic characteristics. Note that this lattice strain can be easily controlled by adjusting not only the type of the underlying film but also the thickness of the ferromagnetic film, the thickness of the underlying film, and the like. Therefore, when a nonmagnetic film such as Cu, a ferromagnetic film having a spin-dependent scattering capability such as a CoFe film, and an antiferromagnetic film are sequentially formed on the ferromagnetic film, a large resistance change is caused by a slight signal magnetic field. It becomes a highly sensitive magnetoresistive effect element. Here, if the resistivity of the base film formed on the substrate is larger than that of the ferromagnetic film, the shunting of the sense current to the base film can be suppressed, and a high resistance change rate is exhibited. Further, if the underlying film does not grow in layers and the smoothness at each interface deteriorates and the rate of change in resistance decreases, another underlying film that has the function of growing the film in layers is used as described above. By interposing between the base film and the substrate, a high resistance change rate can be realized.
[0067]
The magnetoresistive effect element according to the sixth aspect of the invention may be one in which a nonmagnetic film and a ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration.
[0068]
A seventh invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a first nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate, wherein at least one ferromagnetic film Second nonmagnetic films and ferromagnetic films having a thickness different from that of the first nonmagnetic film are alternately formed adjacent to the main surface of the film opposite to the first nonmagnetic film. Provided is a magnetoresistive effect element characterized in that the magnetizations of the ferromagnetic films in the unit laminated film composed of the ferromagnetic film and the second ferromagnetic film are ferromagnetically coupled to each other. .
[0069]
In the seventh invention, at least the second nonmagnetic film and the ferromagnetic film may be formed adjacent to the ferromagnetic films on both sides formed with the first nonmagnetic film interposed therebetween. One side of the non-magnetic film may be a single-layer ferromagnetic film. It is also possible to form a unit laminated film by alternately forming two or more periods of the second nonmagnetic film and the ferromagnetic film adjacent to the main surface of the ferromagnetic film opposite to the first nonmagnetic film. It is. Here, it is preferable that the thickness of the second nonmagnetic film in the unit laminated film is 2 nm or less, and the thickness is such that ferromagnetic films adjacent to each other do not have RKKY-like antiferromagnetic coupling. It is preferable. This is to keep the magnetization of each ferromagnetic film in the unit laminated film in a ferromagnetic coupling state. For example, when the material of the ferromagnetic film is CoFe and the material of the second nonmagnetic film is Cu, the thickness of the second nonmagnetic film is set not to be around 1 nm.
[0070]
In addition, the ferromagnetic film and the second nonmagnetic film are grown while maintaining lattice matching, that is, the ferromagnetic film and the second nonmagnetic film are lattice matched so that there is no extra scattering at the interface between the two. Is desirable. Thereby, an increase in resistance can be prevented.
[0071]
In the seventh invention, the unit laminated film composed of the ferromagnetic film and the second nonmagnetic film has good soft magnetic characteristics, good lattice matching, and is ferromagnetically coupled. Compared to the ferromagnetic coupling state, the resistance is small, and the number of interfaces between the ferromagnetic film and the nonmagnetic film that generate spin-dependent scattering is large. For this reason, an increase in resistance change rate due to so-called bulk scattering in the unit laminated film can be expected. Therefore, an artificial lattice film or a spin valve structure film using this unit laminated film as a ferromagnetic film unit has good soft magnetic characteristics and a high resistance change rate due to spin-dependent scattering. As a result, a highly sensitive magnetoresistive element can be obtained.
[0072]
The magnetoresistive effect element according to the seventh aspect of the invention may be one in which the first nonmagnetic film and the unit laminated film or the ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration. The magnetoresistive element of the seventh invention may have either a spin valve structure film or an artificial lattice film.
[0073]
An eighth invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate. The bias magnetic field applying means includes a bias film formed adjacent to or close to the laminated film, and bias magnetic fields in directions in which the components in the track width direction are antiparallel to each other are applied to the two ferromagnetic films. The magnetoresistive effect element is characterized in that the magnetizations of the two ferromagnetic films are rotated in opposite directions by a signal magnetic field.
[0074]
In the eighth invention, as a method of applying a bias magnetic field in which the magnetizations of the two ferromagnetic films are reversely rotated by the signal magnetic field, a method of forming a bias film adjacent to or close to the laminated film, more specifically, For example, a method using exchange coupling from an antiferromagnetic film, a method using a hard magnetic film, a method using an exchange bias generated by laminating a new ferromagnetic film on a ferromagnetic film having spin-dependent scattering ability, etc. Furthermore, a method using a bias magnetic field generated by a sense current or a magnetostatic coupling (demagnetizing field) generated during fine pattern processing is employed. However, a bias magnetic field is applied to at least one of the ferromagnetic films by forming a bias film as described above.
[0075]
Specifically, for example, an antiferromagnetic film is laminated adjacent to two ferromagnetic films, and this antiferromagnetic film is used so that the direction of the bias magnetic field differs between adjacent ferromagnetic films by 180 °. Each ferromagnetic film is magnetized. Magnetization in this case can be achieved by changing the direction in which a static magnetic field is applied during film formation of the ferromagnetic film and the antiferromagnetic film by 180 °. Here, it is desirable that the bias magnetic field applied to the adjacent ferromagnetic films has a minimum size required for making the ferromagnetic film into a single magnetic domain, for example, 5 kA / m or less. Further, both antiferromagnetic films preferably have different nail points in order to easily apply bias magnetic fields in different directions to the two ferromagnetic films.
[0076]
Alternatively, there is a method shown below. For applying a bias magnetic field to one of the ferromagnetic films, an exchange bias magnetic field formed by stacking with an antiferromagnetic film is used. On the other hand, to apply a bias magnetic field to another ferromagnetic film, a new ferromagnetic film is laminated adjacent to the main surface of the antiferromagnetic film opposite to the ferromagnetic film, and the antiferromagnetic film is laminated. This utilizes a magnetostatic coupling magnetic field (demagnetizing field) generated when a new ferromagnetic film fixed by magnetization is processed into a fine pattern. This new ferromagnetic film includes a ferromagnetic film A (for example, a film having good crystallinity such as NiFe or CoFe) suitable for applying an exchange bias in order from the side in contact with the antiferromagnetic film, and a magnetostatic field. Two layers in which another ferromagnetic film B suitable for generating a coupling magnetic field (for example, a Co-based amorphous ferromagnetic film or a nitrided or carbonized microcrystalline ferromagnetic film) is laminated so as to be ferromagnetically exchange-coupled A structure is desirable. In this two-layer structure, by adjusting the Bs and resistance value of the ferromagnetic film according to the film thickness, composition adjustment, fabrication conditions, etc. of the ferromagnetic film B, for example, Bs is low, and the resistance value is high. The coupling bias magnetic field strength and the so-called shunt bias (operating point bias) generated when a part of the sense current flows through the ferromagnetic film B can be adjusted. In the case where the ferromagnetic film is made of NiFe or the like having an anisotropic magnetoresistance effect, it is preferable that the sense current flow in a direction orthogonal to the direction of the signal magnetic field. That is, in the method of flowing the sense current in the direction perpendicular to the signal magnetic field, the normal anisotropic magnetoresistance effect that cannot be ignored when using a NiFe film or the like and the resistance change due to spin-dependent scattering are superimposed, so ΔR / R increases.
[0077]
In addition, when a bias magnetic field is applied to a ferromagnetic film using an antiferromagnetic film, the problem is that the bias magnetic field is too large. And a laminated film of a nonmagnetic film and a ferromagnetic film having a ferromagnetic film on the antiferromagnetic film side.
[0078]
In the eighth invention as described above, the magnetization between the adjacent ferromagnetic films is sharply changed from the antiparallel state to the parallel state by the signal magnetic field. Furthermore, the bias magnetic field from the antiferromagnetic film or the like necessary for making the magnetization directions antiparallel when the signal magnetic fields of both ferromagnetic films are zero is suppressed to the minimum necessary for suppressing Barkhausen noise. . For this reason, even when a signal magnetic field is applied in the difficult axis direction suitable for the magnetic head (having advantages such as good high frequency characteristics), the magnetization between the two ferromagnetic films has a magnetization of 0 to 180 due to the magnetization rotation of both the ferromagnetic films. Vary in a relatively low magnetic field range up to °. Therefore, a large resistance change rate comparable to that in the easy axis direction is indicated by a relatively low magnetic field range. In the eighth invention, the directions of the bias magnetic fields applied to the two ferromagnetic films are not necessarily antiparallel to each other. In other words, the magnetization directions of the two ferromagnetic films in the case where the signal magnetic field is zero. The angles formed with the signal magnetic field direction may not be set to + 90 ° and −90 °, respectively. Specifically, the angles formed by the magnetization directions of both ferromagnetic films and the signal magnetic field when the signal magnetic field is zero are preferably set within the ranges of + 30 ° to 60 ° and −30 ° to 60 °, respectively. The reason for this is that the operating point bias is not required by tilting the magnetization directions of the two ferromagnetic films when the signal magnetic field is zero so that the angle between the anti-parallel state and the signal magnetic field is within the range as described above. Because.
[0079]
Furthermore, in the conventional spin valve magnetoresistive effect element, the rate of change in resistance increases exponentially as the non-magnetic film thickness decreases, so it is desirable to make the non-magnetic film thickness as thin as possible. However, when the film thickness of the nonmagnetic film is less than 2 nm, the ferromagnetic coupling between the upper and lower ferromagnetic films becomes stronger, the antiferromagnetic magnetization arrangement cannot be realized, and the resistance change rate is greatly reduced. is there. However, in the eighth invention in which a bias magnetic field is applied to both ferromagnetic films, an antiferromagnetic magnetization arrangement can be realized by adjusting the antiparallel bias magnetic field strength even when the film thickness of the nonmagnetic film is less than 2 nm. A dramatic increase in the rate of resistance change can be expected.
[0080]
Further, since a bias magnetic field is applied to the two ferromagnetic films, the domain walls disappear from all the ferromagnetic films, and Barkhausen noise can be suppressed.
[0081]
The magnetoresistive effect element according to the eighth aspect of the invention may be one in which a nonmagnetic film and a ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration.
[0082]
A ninth invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate, wherein the two ferromagnetic films are respectively A magnetization fixed film that substantially retains the magnetization direction even when a signal magnetic field is applied, and a magnetic field detection film that detects a signal magnetic field by changing the magnetization due to the signal magnetic field. There is provided a magnetoresistive effect element characterized in that magnetization directions of magnetic films are substantially orthogonal to each other and a sense current is passed in a signal magnetic field direction.
[0083]
In the ninth aspect of the invention, as a method for fixing the magnetization of the magnetization pinned film, a method of stacking an antiferromagnetic film so as to exchange-couple with the magnetization pinned film, a method of achieving a high Hc of the magnetization pinned film, and a high Hc There is a method of laminating a ferromagnetic film having a pinned magnetic film. In addition, as a method of making the magnetization directions of the magnetization pinned film and the magnetic field detection film perpendicular to each other when the signal magnetic field is zero, a method of providing a magnetization easy axis of the magnetic field detection film so as to be perpendicular to the magnetization of the magnetization pinned film, magnetic field detection For example, a bias film is formed adjacent to or close to the film, and a weak exchange coupling bias of about 5 kA / m or less is applied in a direction orthogonal to the magnetization of the magnetization pinned film. According to the latter method, even when the magnetic field detection film is made of CoFe having a particularly large bias magnetic field, the magnetization easy axis of the magnetic field detection film is provided in substantially the same direction as the magnetization of the magnetization fixed film. By providing an exchange coupling bias slightly in excess of the anisotropic magnetic field of CoFe in the in-plane direction perpendicular to the axis, the magnetic anisotropy of the magnetic field detection film can be reduced, resulting in a large resistance change rate in a low magnetic field range. It becomes possible.
[0084]
In the ninth invention, when the angle between the magnetization of the magnetization fixed film and the signal magnetic field detection film is set to about 90 ° in the state of the signal magnetic field 0, the magnetization of the magnetization fixed film is directed in the direction of the positive signal magnetic field, for example. In the case of a positive signal magnetic field, the angle between magnetizations of adjacent ferromagnetic films becomes ferromagnetic, so that the resistance decreases. Since the angle formed is antiferromagnetic, the resistance increases. That is, no operating point bias is required.
[0085]
Further, when the sense current is passed in the direction of the signal magnetic field, the magnetization of the magnetic field detection film is tilted in the direction perpendicular to the signal magnetic field by the current magnetic field. Therefore, Barkhausen noise can be suppressed due to the current magnetic field applied to the magnetic field detection film. In this case, since there is a current magnetic field, the magnetic field detection film does not necessarily require an easy magnetization axis.
[0086]
The magnetoresistive effect element according to the ninth aspect of the invention may be one in which a nonmagnetic film and a ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration.
[0087]
A tenth aspect of the invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate, wherein the two ferromagnetic films are respectively A magnetization fixed film that substantially retains the magnetization direction even when a signal magnetic field is applied, and a magnetic field detection film that detects the signal magnetic field by changing the magnetization direction by the signal magnetic field. The magnetoresistive element is characterized in that an angle θ formed by the magnetization direction of the ferromagnetic film is 30 ° or more and 60 ° or less.
[0088]
In the tenth invention, as a method for fixing the magnetization of the magnetization fixed film, a method using an exchange bias generated by stacking an antiferromagnetic film on the magnetization fixed film, or a magnetization fixed film, as in the ninth invention, There is a method of using a ferromagnetic film as a high coercive force film. The bias magnetic field applying means to the magnetic field detection film includes an easy axis of magnetization of the magnetic field detection film, a bias magnetic field from a hard magnetic film formed adjacent to or close to the magnetic field detection film, and adjacent to or close to the antiferromagnetic film. The magnetostatic bias generated from the ferromagnetic film formed in this manner, the current magnetic field from the sense current, and the like can be used. In order to use the current magnetic field from the sense current, it is necessary to pass the sense current in substantially the same direction as the signal magnetic field. However, from the viewpoint of stably fixing the magnetization in the magnetization fixed film, the sense current is applied in a direction orthogonal to the signal magnetic field so that the current magnetic field from the sense current is applied in substantially the same direction as the magnetization direction of the magnetization fixed film. It is desirable to do.
[0089]
In the tenth aspect of the invention, the angle θ between the magnetization pinned film and the magnetic field detection film when the signal magnetic field is zero is set within 30 to 60 °, so that the operating point bias is not required due to the leakage magnetic field from the magnetization pinned film. However, Barkhausen noise can be removed. The angle θ formed between the magnetization pinned film and the magnetic field detection film as described above in the tenth invention is set to 30 ° to 60 °. When the angle θ is less than 30 °, the linear response magnetic field range with respect to the signal magnetic field is large. This is because if it is narrowed and exceeds 60 °, Barkhausen noise may not be sufficiently removed.
[0090]
Here, when a sense current flows in a direction orthogonal to the signal magnetic field, the direction of the ferromagnetic coupling magnetic field between the two ferromagnetic films and the direction of the current magnetic field are on the same axis. As a result, if a sense current is applied so that the direction of the magnetic coupling between adjacent ferromagnetic films that cause a decrease in magnetic permeability and the direction of the current magnetic field are substantially the same, in this case, a strong magnetization that is not magnetized is fixed. Since the magnetization direction of the magnetic film rotates in the magnetization direction of the ferromagnetic film that is fixedly magnetized, the angle between the magnetizations of both ferromagnetic films decreases. As a result, even when a material exhibiting an anisotropic magnetoresistance effect is used as the ferromagnetic film, an increase in sensitivity can be expected because the anisotropic magnetoresistance effect and resistance change due to spin-dependent scattering are superimposed. Conversely, if a sense current is applied so that the ferromagnetic coupling direction and the current magnetic field direction are opposite, in this case, the angle formed by the two ferromagnetic films increases, so the linear magnetic field range for the signal magnetic field is increased. Can be expanded. Therefore, it is preferable to appropriately select the direction in which the sense current is applied according to the material of the ferromagnetic film.
[0091]
The magnetoresistive effect element according to the tenth aspect of the invention may be one in which a nonmagnetic film and a ferromagnetic film are alternately laminated a plurality of times in addition to the above configuration.
[0092]
An eleventh invention is a magnetoresistive effect element comprising a laminated film in which at least a ferromagnetic film, a nonmagnetic film, and a ferromagnetic film are sequentially laminated on a substrate. Provided is a magnetoresistive effect element comprising two or more bias films stacked as adjacent to or adjacent to the stacked film as bias magnetic field applying means.
[0093]
In the eleventh invention, the bias film may be formed on the uppermost ferromagnetic film of the laminated film and between the lowermost ferromagnetic film and the substrate, or the uppermost ferromagnetic film of the laminated film. Two or more layers may be formed on the film, or two or more layers may be formed between the lowermost ferromagnetic film and the substrate.
[0094]
In the eleventh invention, examples of the bias film include an antiferromagnetic film and a ferromagnetic film. An exchange coupling magnetic field from such an antiferromagnetic film, an exchange coupling magnetic field from a ferromagnetic film, or a magnetostatic coupling. A magnetic field, a current magnetic field from a sense current, and the like are applied as a bias magnetic field to the ferromagnetic film in the laminated film. Here, when an exchange coupling magnetic field is generated from the ferromagnetic film as the bias film, a film for reducing the exchange bias is disposed between the ferromagnetic film as the laminated film and the ferromagnetic film as the bias film. Alternatively, a ferromagnetic film as the bias film may be directly formed on the laminated ferromagnetic film. However, in the former case, it is preferable that the uniaxial anisotropic magnetic field Hk of the bias film is larger than the uniaxial anisotropic magnetic field Hk of the laminated ferromagnetic film, and the coercive force Hc of the bias film is that of the ferromagnetic film of the laminated film. It is preferably larger than the coercive force Hc.
[0095]
In the eleventh invention, a bias magnetic field is applied to either one of the uppermost layer or the lowermost ferromagnetic film so that the magnetization does not substantially move in the signal magnetic field, and the signal magnetic field is applied to the other. It is preferable to add a bias magnetic field that can be detected and remove Barkhausen noise to form a magnetic field detection film. At this time, a laminated antiferromagnetic film is suitable for applying a bias magnetic field to the magnetization pinned film. A lamination of a ferromagnetic film or an antiferromagnetic film is suitable for applying a bias magnetic field to the magnetic field detection film. Here, the ferromagnetic film as the bias film is a high-resistance soft magnet that is single-domained by any method, such as a Co-based amorphous film that is heat-treated in a rotating magnetic field, and whose magnetization direction is aligned in one direction. A film, a film having a high uniaxial magnetic anisotropy such as a Co or CoFe amorphous film subjected to heat treatment in a static magnetic field, or a high coercive force film is suitable. Also, a high-resistance soft magnetic film with a single magnetic domain can be realized by forming a ferromagnetic film as a bias film wider than other films and laminating a hard magnetic film or an antiferromagnetic film at the edge portion. .
[0096]
In the eleventh aspect of the present invention, a strong bias magnetic field that enables magnetization fixation to a specific ferromagnetic film by further laminating at least two bias films adjacent to or close to the laminated film as described above. Therefore, it is possible to apply a minimum bias magnetic field necessary for removing Barkhausen noise to other specific ferromagnetic films. At this time, in the eleventh invention in which two or more bias films are stacked, for example, compared to a case where only the magnetic field detection film is formed wider than other magnetization fixed films and the bias film is stacked on the edge portion. There is an advantage that a multilayer film including a bias film can be easily manufactured in a short time by batch continuous film formation. This is because it is very difficult to form only the magnetic field detection film by removing only the edge part of the magnetic field detection film having a thickness of about 1 to 20 nm and removing the edge part of other magnetization fixed films. based on.
[0097]
Further, here, when the bias magnetic field applied to the ferromagnetic film is orthogonalized by the two bias films, the angle formed by the magnetization direction of the magnetization fixed film and the magnetic field detection film when the signal magnetic field is zero as in the ninth aspect. Becomes almost 90 °, and no operating point bias is required. Also, Barkhausen noise can be removed by the bias magnetic field applied to the magnetic field detection film, and the magnitude of the bias magnetic field can be easily adjusted by adjusting the magnetic anisotropy and film thickness of the bias film, or the interface between the laminated film and the bias film. Can be controlled. In addition, when a bias magnetic field is applied in a direction substantially perpendicular to the direction of the easy axis of magnetization of the ferromagnetic film, the magnetic permeability of the film can be improved even for a ferromagnetic film made of a Co-based material exhibiting high Hk.
[0098]
According to an eleventh aspect of the present invention, a laminated film in which three layers of ferromagnetic films and two layers of nonmagnetic films are alternately formed is provided on a substrate, and the uppermost layer and the lowermost layer of ferromagnetic films are magnetization fixed films. Thus, the present invention can be preferably applied to a magnetoresistive effect element in which a central ferromagnetic film having a high magnetic permeability serves as a magnetic field detection film.
[0099]
In such a magnetoresistive effect element, the uppermost ferromagnetic film and the lowermost ferromagnetic film are magnetized by two or more bias films formed by further laminating, ie, adjacent to or close to the laminated film. Is fixed, the magnetization direction changes little with respect to the signal magnetic field. On the other hand, since the central ferromagnetic film has a high magnetic permeability, a large magnetization rotation occurs due to a slight magnetic field. As a result, the angle between the magnetization of the uppermost ferromagnetic film and the lowermost ferromagnetic film and the magnetization of the central ferromagnetic film changes sharply due to the signal magnetic field. In addition, the number of interfaces that cause spin-dependent scattering is increased at least twice as compared with a film having a conventional spin valve structure. For this reason, a large resistance change can be obtained with a small magnetic field.
[0100]
Note that if the magnetization of the central ferromagnetic film is fixed by a bias film such as an antiferromagnetic film to reduce the magnetic permeability, the antiferromagnetic film has a high resistivity, so ΔR / R is greatly reduced. When the magnetizations of the upper and lower ferromagnetic films are fixed, the antiferromagnetic film can be arranged outside the spin-dependent scattering unit, so that the magnetization can be fixed without reducing ΔR / R.
[0101]
Furthermore, since the high magnetic permeability ferromagnetic film exists in the vicinity of the center of the laminated film having the spin valve structure, the current magnetic field from the sense current becomes weak, and as a result, the ferromagnetic film that becomes the magnetic field detection film by the current magnetic field becomes weak. The problem that the magnetization arrangement is disturbed can also be avoided.
[0102]
According to a twelfth aspect of the present invention, there is provided a magnetic film comprising: a high coercive force film having a hexagonal C-axis in a film plane; and a ferromagnetic film having a coercive force lower than that of the high coercive force film. A resistance effect element is provided.
[0103]
In the twelfth invention, it is possible to suppress a normal high coercive force film from becoming a high coercive force due to strong magnetostatic coupling due to crystal magnetic anisotropy in the direction perpendicular to the film surface. Thus, when this high coercive force film is a magnetization fixed film in a spin valve structure film, the soft magnetic characteristics of the magnetic field detection film for detecting the signal magnetic field are not deteriorated. Further, the parallel state and antiparallel state of magnetization can be efficiently realized, and the nonmagnetic film thickness in the laminated film can be remarkably reduced, so that the resistance change rate can be increased. Here, the high coercive force film and the nonmagnetic film as the magnetization fixed film may be alternately laminated a plurality of times.
[0104]
Furthermore, since the single crystal-like high coercive force film has a low electric resistance, the output can be increased without affecting the spin-dependent scattering even when it is a laminated film with the low coercive force film. Furthermore, since this single crystal-like high coercive force film has a high magnetocrystalline anisotropy, it has a high magnetic permeability (magnetization is difficult to move), and has a large magnetization fixing effect.
[0105]
In the twelfth invention, the high coercive force film may be used as a bias film for applying a bias magnetic field to the ferromagnetic film. At this time, for example, even when the high coercive force film is used as a bias film for fixing the magnetization of the magnetization fixed film, the soft magnetic characteristics of the magnetic field detection film for detecting the signal magnetic field are not deteriorated. Furthermore, this high coercive force film can be used as a bias film for Barkhausen noise countermeasures, or as a bias film that creates an anti-coupled state of magnetization when there is no signal magnetic field, and can have both functions at the same time. It is. Furthermore, the twelfth invention is not limited to a magnetoresistive element having a laminated film in which a ferromagnetic film and a nonmagnetic film are alternately formed on a substrate, but utilizes an anisotropic magnetoresistive effect such as a NiFe alloy. It can also be applied to a magnetoresistive effect element.
[0106]
Examples of the present invention will be specifically described below.
[0107]
(Example 1)
As a substrate, a sapphire substrate C surface (α-Al) until the average surface roughness is about 2 nm with a stylus type surface roughness meter having a stylus tip radius of 0.2 μm. ₂ O _Three The (0001) surface of the substrate was polished by a mechanochemical polishing method to be in a mirror state.
[0108]
This sapphire substrate is placed in a vacuum chamber, and the inside of the vacuum chamber is 5 × 10 ^-7 Exhaust to below Torr. Thereafter, Ar gas is introduced into the vacuum chamber, the inside of the vacuum chamber is set to about 3 mTorr, and sputtering is performed in a static magnetic field of about 4000 A / m, thereby forming a ferromagnetic material on the sapphire substrate 10 as shown in FIG. Co as a film ₉₀ Fe _Ten Film 11, Cu film 12 as intermediate nonmagnetic film, Co as ferromagnetic film ₉₀ Fe _Ten A film 11, an FeMn film 13 that is an antiferromagnetic film, and a Ti film 14 that is a protective film are sequentially formed, and Ti 5 nm / FeMn 8 nm / Co ₉₀ Fe _Ten 8nm / Cu2.2nm / Co ₉₀ Fe _Ten A laminated film having a spin valve structure of 8 nm was produced to obtain a magnetoresistive element. Further, a Cu lead 15 was formed on the laminated film. Note that the composition of the CoFe-based alloy film exhibits a large rate of resistance change [Journal of the Japan Society of Applied Magnetics, 16 , 313 (1992)] and Co in terms of soft magnetic properties ₉₀ Fe _Ten It was.
[0109]
Here, as a material for the protective film, nonmagnetic materials such as Cu, Cr, W, SiN, and TiN can be used in addition to Ti. In order to prevent the oxidation of FeMn, it is desirable to use a material other than the oxide. Further, the thickness of the Ti film 14 may not be 5 nm as long as it has a protective effect. However, in order to prevent a decrease in sensitivity due to the shunting to the Ti film 14 when a sense current is passed, ₉₀ Fe _Ten Considering that the electric resistivity is higher than that of the film 11, the film thickness is desirably several tens of nm or less.
[0110]
Co in contact with the FeMn film 13 ₉₀ Fe _Ten The film 11 is magnetized and fixed by FeMn, and the other Co ₉₀ Fe _Ten The film 11 reverses and rotates in accordance with the external magnetic field. Co, a ferromagnetic film ₉₀ Fe _Ten The thickness of the film 11 is 8 nm for both layers, but the thickness of the two ferromagnetic films may be the same or different. A ferromagnetic film can be used in principle if the film thickness is one atomic layer (0.2 nm) or more, but 0.5 to 20 nm is practically suitable for MR elements.
[0111]
2 Co ₉₀ Fe _Ten The film thickness of the Cu film 12 formed between the films 11 is 2.2 nm in this embodiment. However, the film thickness may be other than this, and is practically 0.5 to 20 nm. Moreover, Au, Ag, Ru, Cu alloy etc. can be used as materials other than Cu.
[0112]
The FeMn film 13, which is an antiferromagnetic film, is directly in contact with Co ₉₀ Fe _Ten Used to fix the magnetization of the film 11. The film thickness can be used if it is about 1 nm or more, but it is preferably 2 nm to 50 nm from the viewpoint of reliability and practicality. In addition to FeMn, Ni oxide can also be used as a material for the antiferromagnetic film. When Ni oxide is used as the material of the antiferromagnetic film, sputtering can be performed in a mixed gas atmosphere of Ar and oxygen, or by applying an ion beam sputtering method, a dual ion beam sputtering method, etc. An antiferromagnetic film can be formed. In addition, since the Ni oxide film can be satisfactorily formed on the sapphire substrate C surface, the spin valve structure is Ti5 nm / Co. ₉₀ Fe _Ten 8nm / Cu2.2nm / Co ₉₀ Fe _Ten It can also be set to 8 nm / Ni oxide 50 nm. In this case, if the thickness of the Ni oxide film is 1 nm or more, a stable bias magnetic field is applied to Co. ₉₀ Fe _Ten Can be applied to the membrane.
[0113]
The magnetic characteristics, resistance change rate, and crystal structure of the magnetoresistive element were examined. The magnetic characteristics were measured with a vibration magnetometer (VSM) at a maximum applied magnetic field of 1.2 MA / m, and the resistance change rate was measured by a four-terminal resistance measurement method in a static magnetic field. The crystal structure was measured by θ-2θ scan and rocking curve X-ray diffraction method. In VSM and X-ray diffraction, the rate of resistance change was measured for a film patterned in a 1 mm × 8 mm stripe pattern using a metal mask. The resistance change in the magnetic field of the magnetoresistive element was measured by the four probe method.
[0114]
The measurement results of the magnetoresistive effect element are shown in FIG. As can be seen from FIG. 2, when an external magnetic field was applied in the direction of the easy axis, the maximum resistance change rate was about 10%. Moreover, the coercive force of this magnetoresistive effect element was 160 A / m or less. As described above, this magnetoresistive effect element showed a large resistance change of about 10% in a weak magnetic field of about 160 A / m, and it was found that good soft magnetic characteristics and a high resistance change rate were obtained. It was. When an external magnetic field was applied in the hard axis direction, the rate of change in resistance was about 4%, but the coercive force was 80 A / m and the soft magnetic characteristics were extremely good.
[0115]
Moreover, the magnetization curve of this magnetoresistive effect element is shown in FIG. 3 (A) and FIG. 3 (B). As can be seen from FIG. 3A, the coercive force in the easy axis direction is about 160 A / m, and the coercive force in the hard axis direction is about 80 A / m. Further, as can be seen from FIG. 3B, in the easy axis direction, Co in contact with FeMn. ₉₀ Fe _Ten It can be seen that an exchange bias of about 5.3 KA / m is applied to the membrane.
[0116]
In addition, the crystal structure of this magnetoresistive effect element showed strong fcc phase (111) plane orientation (close-packed plane orientation).
[0117]
A Ti / FeMn / CoFe / Cu / CoFe film was formed on the thermally oxidized Si substrate in the same manner as described above. As a result of evaluation in the same manner as described above, the close-packed peak of X-ray diffraction is reduced to 1/10 or less compared to the above case, and Hc is 3000 A / m in the easy axis direction. Is a high value that is difficult to apply, and the rate of change in resistance is 8% or less, which is smaller than that of the (111) alignment film.
[0118]
Next, a Ti / FeMn / CoFe / Cu / CoFe film was produced on the MgO (100) substrate in the same manner as described above. As a result of evaluation in the same manner as described above, the X-ray diffraction peak showed only a high intensity (100) peak, that is, a good (100) orientation. At this time, Hc is 1200 A / m in the easy axis direction, shows a high value that is difficult to apply to the magnetoresistive effect element, and the resistance change rate also shows a value of 8% or less, which is smaller than the above (111) orientation film. It was.
[0119]
From the above, it can be seen that when the (111) orientation is realized, a low Hc and high resistance change rate can be realized.
[0120]
Next, a magnetoresistive effect element having a spin valve structure of Ti 5 nm / FeMn 8 nm / Co 8 nm / Cu 2.2 nm / Co 8 nm using a Co film as a ferromagnetic film was fabricated on a sapphire C-plane substrate, and the magnetic characteristics and When the resistance change rate was measured, the similar close-packed plane orientation and resistance change rate showed a value of about 8%, and the coercive force was about 800 A / m. In the thermally oxidized Si substrate, ΔR / R = 7% and Hc = 2000 A / m.
[0121]
From these results, even if Co is used as the material of the ferromagnetic film, low Hc and high ΔR / R can be obtained, but soft magnetic characteristics are generated by using an alloy in which Fe is added to Co as the material of the ferromagnetic film. This is easier and more desirable.
[0122]
Furthermore, Ti5nm / FeMn8nm / Co _100-x Fe _x 8nm / Cu2.2nm / Co _100-x Fe _x A spin-valve magnetoresistive element made of 8 nm / sapphire C-plane or glass substrate is used as Co. _100-x Fe _x The ferromagnetic film was prepared by changing the Fe concentration x (atomic%). The relationship between ΔR / R and Hc obtained as a result is shown in Table 1 below. As can be seen from Table 1, it is clear that a significant reduction in Hc and an increase in ΔR / R are realized in the range of 5 ≦ x ≦ 40 on the sapphire C surface.
[0123]
[Table 1]

[0124]
(Example 2)
On the C surface of the sapphire substrate, on the glass substrate (# 0211 manufactured by Corning), and on the (111) surface of the Si substrate, a 10 nm-thick Cu underlayer is formed, and the same as in Example 1 is further formed thereon. Co under the deposition conditions ₉₀ Fe _Ten A film was formed. The Cu underlayer can be formed by bias sputtering, ion-assisted ion beam sputtering, vapor deposition, or the like. This Co ₉₀ Fe _Ten The coercivity (Hc) of the film was measured. In addition, a Co base film is provided on each of the substrates to form Co. ₉₀ Fe _Ten The film is formed by variously changing the film thickness, and the Co ₉₀ Fe _Ten The coercivity (Hc) of the film was measured. The result is shown in FIG. Further, various film thicknesses of Co can be formed in the same manner as described above without forming a Cu base film on the substrate. ₉₀ Fe _Ten Films were formed and their coercivity (Hc) was measured. The result is shown in FIG.
[0125]
As can be seen from FIGS. 6 and 7, in any substrate, when the Cu base film is formed (FIG. 6), the Hc is lower than when the Cu base film is not present. In addition, it can be seen that regardless of the presence or absence of the Cu underlayer, Hc is low and favorable in the order of the C surface of the sapphire substrate, the (111) surface of the Si substrate, and the glass substrate. In particular, 8 nm thick Co is applied to the C surface of the sapphire substrate via a Cu underlayer. ₉₀ Fe _Ten When the film was formed, a low Hc of 80 A / m or less was exhibited. In addition, Co having a Cu underlayer ₉₀ Fe _Ten The Hc of the film is Co ₉₀ Fe _Ten There was a tendency to increase slightly as the film thickness increased. On the other hand, Co without a Cu underlayer ₉₀ Fe _Ten The Hc of the film first decreased as the film thickness increased, and further increased as the film thickness increased. For example, Co ₉₀ Fe _Ten When the film thickness was about 8 nm, the minimum value of Hc was 160 A / m or less.
[0126]
Thus, it can be seen that good soft magnetic properties can be obtained by forming a base film between the two when forming a ferromagnetic film on the substrate.
[0127]
Co on the C surface of the sapphire substrate or on the Si substrate ₉₀ Fe _Ten It has been found that good soft magnetic characteristics can be obtained by using a CuNi alloy film as a base film when forming a film or a Co film. Co on glass substrate or ceramic substrate ₉₀ Fe _Ten It can be seen that by using a Ge, Si, or Ti film of several to 100 nm as a base film when forming a film or Co film, close-packed surface orientation is promoted, and as a result, good soft magnetic properties can be obtained. It was.
[0128]
Co ₉₀ Fe _Ten By using a material having a higher resistance than the film or Co film for the base film, it is possible to prevent the MR sense current from being shunted. For example, the Ni oxide film described in Example 1 has a high resistance and is an antiferromagnetic film that can be epitaxially grown on the C-plane of the sapphire substrate, so that it also serves as the base film and the antiferromagnetic bias film. Can do. FIG. 8 shows a magnetoresistive element having a spin valve structure using the Ni oxide film 26.
[0129]
(Example 3)
Co ₉₀ Fe _Ten The influence of the plane orientation of the sapphire substrate on the coercive force exhibited by the film was investigated. In this example, the C plane and the R plane (α-Al ₂ O _Three Comparison was made on the (1012) surface of the substrate.
[0130]
Co with a thickness of 10 nm ₉₀ Fe _Ten A film was formed on each of the C and R surfaces of the sapphire substrate. 9A and 9B show the difference in crystal orientation depending on the plane orientation. As can be seen from FIG. 9A, a good fcc (111) orientation can be realized on the C-plane, and as a result, a CoFe alloy film having a good soft magnetic property with a coercive force of 160 A / m or less could be formed. . On the other hand, as can be seen from FIG. 9B, on the R plane, the fcc (200) peak is detected in addition to the fcc (111) peak, and the fcc (111) orientation is not very good. For this reason, the coercive force was several hundred A / m or more, and good soft magnetic properties could not be obtained.
[0131]
9A, in addition to the peak of the sapphire that is the substrate, only the peak corresponding to the fcc phase (111) plane is included in the vicinity of 2θ = 43.5 ° on the C plane (some hcp phase (001) plane orientation may be included). ) Appears strongly. In addition, the stronger this peak intensity is, the more Co ₉₀ Fe _Ten The film showed a low coercivity. On the other hand, in FIG. 9B, on the R plane, in addition to the sapphire peak and the fcc phase (111) plane peak, a peak corresponding to the fcc phase (200) plane appears near 2θ = 52.6 °. The presence of this fcc phase (100) plane orientation means that the easy axis of magnetocrystalline anisotropy appears in the plane, which causes an increase in coercive force.
[0132]
Next, Co on the C surface of the sapphire substrate ₉₀ Fe _Ten The rocking curve was measured for the peak corresponding to the (111) plane (closest packed plane) of the film. The rocking curve is shown in FIG. As can be seen from FIG. 10, a very strong orientation with a peak at around θ = 21.8 ° and a half width of about 3 ° can be confirmed. The peak of the sapphire substrate overlaps with this rocking curve, but Co ₉₀ Fe _Ten A good crystal orientation of the film can be confirmed.
[0133]
Next, in FIG. ₉₀ Fe _Ten Coercivity of the film and Co ₉₀ Fe _Ten The correlation with the half value width in the rocking curve of the peak corresponding to the (111) plane (closest packed plane) of the film is shown. As can be seen from FIG. 11, Co on the glass substrate. ₉₀ Fe _Ten When the film was formed, the (111) peak was often weak, the rocking curve half-width was 20 ° or more, and Hc was 3000 A / m or more. Further, when the Ar pressure and the substrate temperature are optimized and the full width at half maximum of the rocking curve is about 15 °, Hc decreases to about 1000 A / m. This Co ₉₀ Fe _Ten When a film made of a material in which about 1% of Al is added to the glass substrate is formed on the glass substrate, the full width at half maximum is reduced to about 8 °, and Hc is about 350 A / m. In addition, Co on the C surface of the sapphire substrate ₉₀ Fe _Ten By forming a film, the half width is further reduced to about 3 °, and Hc is about 160 A / m. Therefore, the closest surface (Co ₉₀ Fe _Ten It can be confirmed that the coercive force tends to decrease rapidly as the full width at half maximum of the peak rocking curve corresponding to the (111) plane in the case of the film decreases to less than 20 °. For example, it can be seen that the full width at half maximum of the rocking curve is 7 ° or less, and the coercive force approaches 160 A / m, which is a good value. That is, Co ₉₀ Fe _Ten As the close-packed surface orientation of the film becomes stronger, Co ₉₀ Fe _Ten The coercivity of the film is reduced. Thus, it can be seen that good soft magnetic properties have a strong correlation with the degree of orientation of the ferromagnetic film.
[0134]
Co ₉₀ Fe _Ten As described above, the method for strengthening the close-packed plane orientation of the film includes, as described above, first a method of adding various additive elements described later, second a method of selecting a substrate material and orientation, and third a substrate and Co. ₉₀ Fe _Ten There are several methods such as a method of providing a base film between the films, and fourth, a method of forming a film by an ultra-high vacuum film forming apparatus such as MBE. In the second method, when the C surface of the sapphire substrate is used as the substrate, the surface is polished with mechanochemical polish, float polish, ion polish or the like to reduce the average surface roughness (Ra) of the substrate to 2 nm or less. The Co formed on it ₉₀ Fe _Ten It has been found that the film exhibits better soft magnetic properties. However, when the average surface roughness is 5 nm or more, Co ₉₀ Fe _Ten The coercive force of the film was 1000 A / m or more.
[0135]
(Example 4)
In Example 3, Co ₉₀ Fe _Ten It was found that the coercive force of the single-layer film was lowered by increasing the close-packed surface orientation by the first and second methods. Next, Co ₉₀ Fe _Ten It is confirmed whether the same can be said for a laminated film including a film.
[0136]
Al-containing Co on glass substrate ₉₀ Fe _Ten 10nm / Cu5nm / Al-containing Co ₉₀ Fe _Ten A 10 nm laminated film was formed under the same film forming conditions as in Example 1. Co in this case ₉₀ Fe _Ten Al element addition amount in the film and Co ₉₀ Fe _Ten The relationship with the coercive force of the film is shown in FIG. As can be seen from FIG. 12, the coercive force can be reduced also by adding Al element in the laminated film. Similarly, in the second to fourth methods shown in the second embodiment, the Co in the laminated film is similarly used. ₉₀ Fe _Ten The orientation of the close-packed surface of the film could be strengthened.
[0137]
Next, Co in the laminated film ₉₀ Fe _Ten The dependence of the coercivity of the film on the close-packed surface peak intensity is shown in FIG. As can be seen from FIG. 13, it can be confirmed that the coercive force decreases as the close-packed surface peak intensity increases as in the case of the single layer film. In the case of the above structure, the peak intensity is 10 ² (Au) is weak and the coercive force is 10 ^Three It is about A / m. In this case, Co ₉₀ Fe _Ten In addition, the coercive force was reduced to about several hundred A / m by using a film made of a material in which about 1 atomic% of Al was added. Further, by replacing the glass substrate with the C surface of the sapphire substrate, 10 ^Three (Au) The above peak intensity and a good coercive force of 100 A / m or less were obtained. In addition, the half value width at this time was 7 degrees or less.
[0138]
(Example 5)
Co ₉₀ Fe _Ten The coercive force was examined by adding an additive element other than Al. In this case, a decrease in coercive force was also observed when Ta, Pd, Zr, Hf, Mo, Ti, Nb, Cu, Rh, Re, In, B, Ru, Ir, and W were used as additive elements. . Moreover, even when combinations of these elements, for example, Ta and Pd, Nb and Pd, and Zr and Nb were added, a decrease in coercive force could be confirmed. As an example, Ta-containing Co ₉₀ Fe _Ten 10nm / Cu5nm / Ta-containing Co ₉₀ Fe _Ten FIG. 14 shows the relationship between the amount of Ta added and the coercive force in a 10 nm stacked film structure. As can be seen from FIG. 14, even in this case, it can be confirmed that the coercive force is reduced by the addition of Ta element.
[0139]
(Example 6)
The above is an example in which (111) high orientation is realized with respect to the CoFe film. However, the present invention is not limited to the CoFe film. Examples thereof are shown in Table 2 below. Table 2 shows (1) the composition of the ferromagnetic film, (2) the type of the substrate, and (3) the structure similar to that shown in FIG. 1 (in contact with the FeMn film) using the base film between the substrate and the spin valve film as parameters. (111) peak rocking curve half-value width Δθ in a spin valve film having a CoFe film) ₅₀ The Hc and ΔR / R in the easy axis direction are shown. For comparison, Table 2 also shows the results when a spin valve film of a ferromagnetic film having the same composition as in Table 2 was formed on a glass substrate without a base film.
[0140]
[Table 2]

[0141]
As can be seen from Table 2, not only a CoFe film but also a CoFeNi film or a CoNi film can be formed by using a base film made of Ti, Si, Ge or the like on a sapphire C-plane substrate, as compared with direct film formation on a glass substrate. , △ θ ₅₀ A favorable (111) orientation film of <7 ° can be obtained, with the result that Hc is reduced and a high resistance change rate can be realized.
[0142]
However, (111) highly oriented (M 1nm thickness / Cu 1nm thickness) due to the underlying film made of Ti or the like or sapphire C-plane substrate ₁₆ An artificial lattice film was fabricated (M: Co ₂₀ Ni ₈₀ , Co ₂₀ Fe ₁₅ Ni ₆₅ ), ΔR / R showed a remarkably small value of 2% or less, and the high saturation magnetic field peculiar to RKKY-like antiferromagnetic coupling disappeared. It can be seen that when the (111) orientation is obtained, the rate of change in resistance is reduced because RKKY-like antiferromagnetic coupling cannot be obtained. Therefore, it is not limited to spin-valve films and does not use RKKY-like antiferromagnetic coupling (so-called uncoupled artificial lattice film using the difference in coercive force (The 14th Annual Meeting of the Japan Society of Applied Magnetics, 1990, 177)))), it is easy to achieve both a high resistance change rate and good soft magnetism.
[0143]
In addition to this, it was confirmed that the same effect can be obtained by replacing the ferromagnetic film in contact with FeMn with a film having the same composition as the lower magnetic film.
[0144]
(Example 7)
A spin valve film of Ti 5 nm / FeMn 8 nm / CoFe 8 nm / Cu 2.2 nm / ferromagnetic film 8 nm was formed on the glass substrate (without the base film) under the same conditions as in Example 1. The relationship between the nonmagnetic additive element added to the lower ferromagnetic film, the resistance change rate in the easy axis direction, and Hc is shown in Table 3 below.
[0145]
[Table 3]

[0146]
As can be seen from Table 3, Hc was lower than that of the film not added with the nonmagnetic element formed on the glass substrate. When Al, Ta, etc. are added, the decrease in Hc is remarkable. However, when a large amount is added, the resistance change rate is greatly reduced. It can be seen that Al is less than 6.5 atomic%, Ta is less than 10 atomic%, and a resistance change rate of 5% or more exceeding NiFe spin valve film and low Hc can be achieved. When Al or Ta was added to CoFe, the peak density of the closest packed surface increased in X-ray diffraction. On the other hand, Cu, Au, Ag, Pd, etc. are not as prominent as Hc reduction effects as Al or Ta, but the resistance change rate does not decrease even when added in a large amount of 10 atomic% or less. The addition of Cu, Au, Ag, Pd or the like to CoFe also increased the close-packed surface peak intensity in X-ray diffraction. It is considered that the decrease in Hc is attributed to the above-described improvement in crystal orientation, because the close-packed surface peak intensity in X-ray diffraction was improved by the additive element. In addition to this, the decrease in magnetocrystalline anisotropy due to the additive element may be due to the decrease in Hc.
[0147]
Furthermore, when the corrosion resistance of each single-layer ferromagnetic film (thickness: 100 nm) was examined by being left in a constant temperature and humidity chamber at 65 ° C. and 95% RH for 100 hours, no discoloration was observed in the film added with 7 atomic% or more of Pd. However, a CoFe film without addition of a nonmagnetic element, Co ₂₀ Ni ₈₀ Membrane, Co ₂₀ Fe ₁₅ Ni ₆₅ Discoloration was observed in the film, the film added with 6.5 atomic% of Al, the film added with 6 atomic% of Ta, and the like. That is, the addition of Pd exhibits the effect of improving the corrosion resistance. Although the decrease in Hc is not so remarkable when only Pd is added, when Pd is added together with Cu, for example, it is possible to further improve the soft magnetic characteristics while maintaining a high resistance change rate and corrosion resistance. Furthermore, when a sapphire C-plane substrate, an amorphous metal underlayer, or an fcc lattice underlayer is used, Hc is reduced to less than 80 A / m even when only Pd is added, and further, in a Pd concentration range up to 40 at% of Pd. A high resistance change rate of 10% was exhibited. However, when Pt, which is expected to be effective in improving the corrosion resistance with the same noble metal, was added, Hc increased more than the film without addition of Pt. For this reason, addition of Pt is not preferable from the viewpoint of soft magnetic properties.
[0148]
(Example 8)
Surface roughness is R _a = After cleaning the surface of thermally oxidized Si substrate of 2 nm or less by SH (mixed solution of sulfuric acid and hydrogen peroxide) treatment, this substrate was placed in a vacuum apparatus and 1 × 10 ^-9 Exhaust to below Torr. Water and oxygen in the vacuum apparatus were controlled by a mass analyzer and a dew point meter. After the above procedure is completed, ultra high purity Ar gas is introduced into the apparatus, and the degree of vacuum in the apparatus is set to 1 × 10. ^-Four Sputtering is performed with an ion beam accelerated by generating a 2.45 GHz microwave discharge inside the ECR ion source as shown in FIG. 15, and as a first underlayer 151 on the thermally oxidized Si substrate 150, as shown in FIG. An amorphous Si film was formed with a film thickness of 5 nm. After that, a Cu—Ni alloy was formed to a thickness of 2 nm as the second base film 152 on the first base film 151 continuously while maintaining a vacuum.
[0149]
As a first ferromagnetic film 153 on the surface, Co ₉₀ Fe _Ten The alloy film is 8 nm thick, the non-magnetic film 154 is a Cu—Ni alloy film is 2.2 nm thick, and the second ferromagnetic film 155 is Co. ₉₀ Fe _Ten An alloy film having a thickness of 8 nm, an Fe-Mn alloy film having a thickness of 8 nm as the antiferromagnetic film 156, and a Ti film having a thickness of 5 nm as the protective film 157 were sequentially formed to produce a spin valve structure laminated film. . All of the above thin films were formed by ion beam sputtering. Further, by forming Cu electrodes 158a and 158b on the laminated film, a spin valve magnetoresistive element 159 was obtained.
[0150]
The composition of the CoFe-based alloy film in the ferromagnetic films 153 and 155 is Co in view of a large resistance change rate (Journal of Japan Applied Magnetics Society: 16.313 (1992)) and soft magnetic characteristics. ₉₀ Fe _Ten It was.
[0151]
When the crystallinity, magnetic characteristics, and resistance change rate of the spin valve magnetoresistive effect element thus obtained were measured, the half-value width by X-ray diffraction of the CoFe alloy film was 1 °, and the physical properties exhibiting soft magnetic characteristics. One of the coercive forces was 0.1 Oe. The magnetoresistance change rate measured using this element showed a high value of about 10%.
[0152]
For comparison, a substrate subjected to the same treatment is placed in a vacuum apparatus, and 1 × 10 ^-7 After exhausting to below Torr, normal Ar gas is 2 × 10 ^-3 Introduced up to Torr, without forming an amorphous Si film on the surface of the substrate, a Cu film was directly formed as a base film, and a laminated film with a spin valve structure having the same configuration as that of Example 8 was formed on the surface. did. Further, a Cu electrode was formed on this laminated film to obtain a magnetoresistive element. This laminated film was formed by a normal bipolar sputtering method excited at 13.56 MHz.
[0153]
When the crystallinity, magnetic characteristics, and resistance change rate of this magnetoresistive effect element were measured, the half-value width by X-ray diffraction of the CoFe alloy film was 7 °, and the coercive force, which is one of the physical properties showing soft magnetic characteristics, was 1.5 Oe. The magnetoresistance change rate measured using this element was about 5%.
[0154]
Example 9
Surface roughness is R _a = After cleaning the surface of a sapphire substrate of 2 nm or less, this substrate is placed in a vacuum apparatus and 1 × 10 ^-9 Exhaust to below Torr. Water and oxygen in the vacuum apparatus were controlled by a mass analyzer and a dew point meter. After the above procedure was completed, an amorphous CuTi film having a film thickness of 3 nm was formed as a first base film by an ultrahigh vacuum deposition method using an electron beam evaporation source. Thereafter, an FeMn alloy film having a film thickness of 2 nm was formed as a second underlayer using ultrahigh vacuum RF sputtering with an excitation frequency of 100 MHz continuously while maintaining a vacuum.
[0155]
Next, Ti5 nm / FeMn8 nm / (Co ₈₁ Fe ₉ ) Pd _Ten 8nm / Cu2.2nm / (Co ₈₁ Fe ₉ ) Pd _Ten A spin-valve magnetoresistive effect element is fabricated by forming an all-stack film with a spin valve structure of 8 nm by using ultrahigh vacuum RF sputtering with an excitation frequency of 100 MHz and further forming a Cu electrode on the laminate film. did.
[0156]
When the crystallinity, magnetic characteristics, and resistance change rate of the spin valve magnetoresistive element thus obtained were measured in the same manner as in Example 8, the half-value width by X-ray diffraction of the CoFe film was 1.5 °. The coercive force, which is one of the physical properties showing soft magnetic properties, was 1 Oe. Moreover, the magnetoresistance change rate measured using the element showed a high value of about 12%.
[0157]
(Example 10)
As shown in FIG. 16, a high-resistance amorphous layer 31 made of CoZrNb or the like is formed on a support substrate 30, and a ferromagnetic film 32 made of CoFe alloy or the like, a nonmagnetic film 33 made of Cu or the like, A magnetic film 32 and an exchange bias layer 34 made of FeMn or the like were sequentially formed in a static magnetic field of about 4 kA / m, and leads 35 were formed on the exchange bias layer 34 to produce a magnetoresistive effect element. Each layer was formed by a four-element sputtering apparatus under the film formation conditions shown in Table 4 below.
[0158]
[Table 4]

[0159]
The magnetic characteristics of this magnetoresistive effect element were examined, and the MH curve (magnetization-magnetic field curve) is shown in FIGS. 17 shows an MH curve in the easy axis direction, and FIG. 18 shows an MH curve in the hard axis direction.
[0160]
As can be seen from FIG. 17, the coercive force Hc (a in the figure) of the CoFe film not fixed to FeMn is about 500 A / m, which is significantly lower than the Hc of about 1600 A / m of a normal CoFe single layer film. showed that. Further, in the direction of the hard axis on the signal magnetic field input side, as can be seen from FIG. 18, the coercive force Hc (b in the figure) of the CoFe film not fixed to FeMn is about 600 A / m. The value was significantly lower than the Hc of the layer film of about 1600 A / m.
[0161]
Further, the resistance change characteristic of this magnetoresistive effect element was examined, and its RH curve (resistance-magnetic field curve) is shown in FIG. As can be seen from FIG. 19, the resistance change rate ΔR / R was as high as about 9%, which is the same as that of the conventional Co-based spin valve film. Further, the coercive force Hc (c in the figure) of the CoFe film not fixed to FeMn was a low value of about 500 A / m as expected from FIG.
[0162]
In this embodiment, the FeMn film is used as the exchange bias layer. However, an antiferromagnetic film such as NiO may be used, or an artificial lattice film having a structure such as (Co / Cu) n may be used. It was confirmed that good characteristics can be obtained. Further, in this embodiment, a CoZrNb film is used as the high-resistance amorphous layer. In addition, a microcrystalline FeZr film, FeZrN film, CoZrN film, FeTaC film, or NiFeX film (X: Rh, Nb, Zr, Hf, Ta, Re, Ir, Pd, Pt, Cu, Mo, Mn, W, Ti, Cr, Au, or Ag) may be used. In particular, the fcc phase microcrystalline film (Co-based nitride film, Co-based carbide film, NiFeX film) also synergizes with the effect of promoting the fcc phase (111) orientation, and the Hc is reduced to about 250 A / m in the easy axis direction. The resistance change rate was improved to 10%.
[0163]
For comparison, the magnetic resistance of a magnetoresistive effect element in which a ferromagnetic film, an intermediate layer, a ferromagnetic film, and an exchange bias layer similar to those shown in FIG. The characteristics were examined, and their MH curves are shown in FIG. 20 and FIG. 20 shows an MH curve in the easy axis direction, and FIG. 21 shows an MH curve in the hard axis direction. The film forming conditions were the same as those in Table 3.
[0164]
As can be seen from FIG. 20, the coercivity Hc (d in the figure) of the CoFe film not fixed to FeMn was about 2000 A / m, which was as high as the Hc of the normal CoFe single layer film. Further, also in the hard axis direction, as shown in FIG. 21, the coercive force Hc (e in the figure) of the CoFe film not fixed to FeMn is about 1400 A / m, which is equal to the Hc of the normal CoFe single layer film. Similarly, it showed a high value and was insufficient as a magnetoresistive element.
[0165]
(Example 11)
As shown in FIG. 22, a base film 36 made of Cu or the like and having a thickness of about 5 nm is formed on a support substrate 30, and an exchange bias layer 34, a ferromagnetic film 32, a nonmagnetic film 33, a ferromagnetic film is further formed thereon. 32 and a high-resistance amorphous layer 31 were sequentially formed, and leads 35 were formed on the high-resistance amorphous layer 31 to produce a magnetoresistive effect element. The film forming conditions were the same as in Table 3 above.
[0166]
Even when the structure shown in FIG. 22, that is, when the high-resistance amorphous layer is formed as an upper layer than the exchange bias layer, low Hc can be obtained. Further, since the amorphous layer has a high resistance, even if this layer is the uppermost layer, there was no decrease in magnetoresistance change rate due to the shunt effect. In this case, it is desirable to provide a base film for controlling the crystal orientation of FeMn.
[0167]
(Example 12)
A CoPtCr film 42 having a thickness of 8 nm is formed on the support substrate 41, a resist 43 is applied thereon, and then the resist 43 is patterned into a desired pattern. As shown in FIG. Etched. At this time, the taper angle X of CoPtCr is desirably close to 90 °.
[0168]
Next, as shown in FIG. 25B, the etched resist 43 is not removed, and in this state, a ferromagnetic film 44 made of a CoFe alloy, a nonmagnetic film 45 made of Cu or the like, a ferromagnetic film 44, and A high resistance amorphous layer 46 was sequentially formed to produce a magnetoresistive element having a spin valve structure. At this time, the taper angle Y of the resist 43 is desirably close to 90 °.
[0169]
Next, after the resist 43 was removed, leads 47 were formed on the high resistance amorphous layer 46. The lead 47 may be formed before the resist 43 is removed. By manufacturing in this way, as shown in FIG. 25C, a spin valve structure sensitive to the interface state can be manufactured without deterioration of characteristics.
[0170]
As in the above structure, a high coercive force film can be used without using an exchange bias layer made of FeMn or the like as a magnetization fixed film. As a material for the high coercive force film, it is desirable to use a material that can exhibit an appropriate in-plane magnetic anisotropy without using a base film. Therefore, in this example, a CoPtCr film satisfying this characteristic was used as the high coercive force film.
[0171]
(Example 13)
As shown in FIG. 24, a high-resistance amorphous layer 31, a ferromagnetic film 32, a nonmagnetic film 33, a ferromagnetic film 32, and a high-resistance amorphous layer 31 are sequentially stacked on a support substrate 30. A lead 35 was formed on the layer 31 to produce a magnetoresistive element.
[0172]
As in the structure shown in FIG. 24, the ferromagnetic film 32 is used by utilizing the self-bias effect due to the effect of the demagnetizing field due to the magnetic field generated by the sense current or the shape without using the exchange bias layer made of FeMn as the magnetization pinned film. An antiferromagnetic magnetization arrangement between them may be realized.
[0173]
In this case, the magnetic field generated by the sense current is applied so as to be opposite in the vertical direction across the ferromagnetic film 32 in the film width direction (g direction in the figure), and further the demagnetizing field in the film width direction is reduced. Therefore, the two ferromagnetic films 32 are antiferromagnetically coupled to each other. As a result, the two ferromagnetic films 32 can be antiferromagnetically coupled without an exchange bias layer. Therefore, when the signal magnetic field Hs is applied in the film longitudinal direction (f direction in the figure), the magnetizations of the two ferromagnetic films 32 rotate and align in the film longitudinal direction to form a ferromagnetic coupling. As a result, a large ΔR / R resulting from spin-dependent scattering can be obtained.
[0174]
(Example 14)
As shown in FIG. 25, a CoCr alloy film having a thickness of 1 nm was formed as a high-resistance ferromagnetic film 161 on a thermally oxidized Si substrate 160 by ion beam sputtering. Next, a CoFe alloy film having a thickness of 3 nm as the first ferromagnetic film 162, a Cu film having a thickness of 2 nm as the nonmagnetic film 163, and a CoFe alloy as the second ferromagnetic film 164 are formed on the high-resistance magnetic film 161. Alloy films were sequentially formed at a thickness of 3 nm to form a spin valve type laminated film.
[0175]
Thereafter, an FeMn film having a thickness of 15 nm was formed as an antiferromagnetic film 165 on the laminated film. A spin-valve magnetoresistive effect element 168 was fabricated by forming a protective film 166 thereon as necessary and further forming electrodes 167a and 167b (interval: 10 μm).
[0176]
When the resistance change rate of the spin valve magnetoresistive element thus obtained was measured, it showed a high value of 14% at room temperature.
[0177]
For comparison, a spin valve magnetoresistive effect element was manufactured in the same manner as in Example 14 except that the high-resistance ferromagnetic film 161 was not formed. When the characteristics of this spin-valve magnetoresistive element were evaluated in the same manner as in Example 14, the rate of change in resistance at room temperature was 12%.
[0178]
(Example 16)
Co as a first ferromagnetic film on a sapphire substrate ₉₀ Fe _Ten Alloy film, Cu film as nonmagnetic film, Co as second ferromagnetic film ₉₀ Fe _Ten An FeMn film was sequentially formed as an alloy film and an antiferromagnetic film. At this time, the thicknesses of the first and second ferromagnetic films (d _FeCo ) To change the resistance change rate (Δρ / ρ ₀ ) Was measured. The result is shown in FIG. The first and second ferromagnetic films have the same thickness, the Cu film has a thickness of 2.2 nm, and the FeMn film has a thickness of 15 nm. In the magnetoresistive element, an electrode is formed on the antiferromagnetic film through a protective film made of Ta, Ni, NiCr or the like having excellent corrosion resistance, if necessary. As can be seen from FIG. 26, d _FeCo It can be seen that the MR effect is increased at 5 nm or less. D _FeCo A peak is taken around 3 nm, and 2 to 4 nm is a preferred range.
[0179]
As the thickness of the sandwich structure of the ferromagnetic film / nonmagnetic film (metal thin film) / ferromagnetic film becomes thinner, electron scattering on the surface not in contact with the metal thin film increases, and the size effect of the resistance appears. For the specific resistance fluctuation (Δρ) of the sandwich structure, the total thickness of the sandwich structure is t, and the mean free path is l. ₀ Then, Δρ is l ₀ Proportional to / t. Although it varies depending on various conditions, as is apparent from FIG. 26, when a Co-based ferromagnetic film is used, the ferromagnetic film thickness is preferably 5 nm or less in order to obtain a good MR effect.
[0180]
That is, when a material having a low resistance, for example, a specific resistance of 30 μΩcm or less, is in contact with the surface of the ferromagnetic film that is not in contact with the metal thin film, electrons pass through the interface and have a specific resistance of 30 μΩcm or less. It will flow into the material, making effective surface scattering less likely. For this reason, in order to cause effective surface scattering and to use the size effect, it is effective to use a material of 30 μΩcm or more or a film thickness of the material in contact with the film to 5 nm or less.
[0181]
In order to obtain a large MR effect using the size effect, the thickness of the Co-based ferromagnetic film is preferably 5 nm or less. At this time, it is desirable to use a metal having a small specific resistance such as Cu, Ag, Au, etc. as the intermediate metal thin film, and the film thickness of the intermediate metal thin film is preferably thinner than 5 nm in order to utilize the size effect. Further, when the film thicknesses of the two ferromagnetic films are greatly different, the effect of surface scattering in the two ferromagnetic films is different, so that the magnetoresistance change rate is reduced. For this reason, it is desirable that the ratio of the thicknesses of the two ferromagnetic films is between 1: 1 and 1: 2.
[0182]
(Example 16)
As shown in FIG. 27, a CuPd alloy film having a thickness of 2 nm was formed on the sapphire substrate 160 as a nonmagnetic film 161 by RF sputtering. Next, a CoFe alloy film having a thickness of 1 nm as the first ferromagnetic film 162, a Cu film having a thickness of 2 nm as the nonmagnetic film 163, and a CoFe alloy as the second ferromagnetic film 164 are formed on the nonmagnetic film 161. The films were sequentially formed at a thickness of 3 nm to form a spin valve type laminated film.
[0183]
Thereafter, an FeMn film having a thickness of 15 nm was formed as an antiferromagnetic film 165 on the laminated film. A spin-valve magnetoresistive element 171 was produced by forming a protective film 166 thereon as necessary and further forming electrodes 167a and 167b.
[0184]
In this magnetoresistive effect element, the antiferromagnetic film 165 imparts unidirectional anisotropy to the second ferromagnetic film 164. Therefore, in a low magnetic field, the magnetization remains fixed in one direction. . On the other hand, the first ferromagnetic film 162 directs magnetization in the direction of the magnetic field even in a low magnetic field. Therefore, by changing the external magnetization, the angle formed by the magnetizations of the two ferromagnetic films can be freely controlled. The antiferromagnetic film 165 preferably has a thickness of about 1 to 50 nm in order to give effective unidirectional anisotropy to the second ferromagnetic film 164.
[0185]
When the resistance change rate of the spin valve magnetoresistive element 171 obtained in this way was measured, it was 8% at room temperature even though the thickness of the first ferromagnetic film 162 was reduced to 1 nm. High value was shown. Further, when the spin valve magnetoresistive element 171 was processed into a fine shape with a width of 2 μm and a length of 80 μm and used for reproducing high-density magnetic recording with a narrow track width in which the distance between Cu leads was 2 μm, Hausen noise could be removed.
[0186]
For comparison, a spin valve magnetoresistive element was fabricated in the same manner as in Example 17 except that the nonmagnetic film 161 was not formed. When the characteristics of this spin-valve magnetoresistive element were evaluated in the same manner as in Example 17, the resistance change rate was only as small as 3% at room temperature.
[0187]
A spin valve magnetoresistive element was fabricated in the same manner as in Example 16 except that the film thickness of the first ferromagnetic film 162 was changed to 6 nm. The characteristics of the spin valve magnetoresistive element were evaluated in the same manner as in Example 16. As a result, the rate of change in resistance was 6% at room temperature. When reproducing (narrow track width), Barkhausen noise due to a demagnetizing field was observed.
[0188]
(Example 17)
As shown in FIG. 28, a thin film 172 having a long mean free path on a thermally oxidized Si substrate 160 has a carrier concentration of 10 ²⁰ cm ^-3 A Te-doped GaAs film was formed to a thickness of 10 nm by the MBE method. Next, a CoFe alloy film having a thickness of 1 nm as the first ferromagnetic film 162, a Cu film having a thickness of 2 nm as the nonmagnetic film 163, and a CoFe alloy as the second ferromagnetic film 164 are formed on the Te-doped GaAs film 172. The films were sequentially formed at a thickness of 4 nm to form a spin valve type laminated film.
[0189]
Thereafter, an FeMn film having a thickness of 15 nm was formed as an antiferromagnetic film 165 on the laminated film. A spin-valve magnetoresistive effect element 173 was produced by forming a protective film 166 thereon as necessary and further forming electrodes 167a and 167b.
[0190]
When the resistance change rate of the spin valve magnetoresistive element thus obtained was measured, it showed a high value of 18% at room temperature. Further, the spin valve magnetoresistive element is used for reproducing high density magnetic recording. ^Five A / cm ² When the output signal voltage was measured at a sense current with a current density of 1 mV _pp A good value was obtained.
[0191]
For comparison, a spin valve magnetoresistive element was fabricated in the same manner as in Example 17 except that the Te-doped GaAs film 172 was not formed. When the characteristics of this spin-valve magnetoresistive element were evaluated in the same manner as in Example 17, the resistance change rate was only as small as 2% at room temperature.
[0192]
(Example 18)
A Cu film having a thickness of 10 nm is formed on a glass substrate as a base film, and a Co film is formed thereon. ₉₀ Fe _Ten A film was formed. Cu film and Co ₉₀ Fe _Ten The film was formed by RF bipolar sputtering. Sputtering was performed under the sputtering conditions shown below by applying a unidirectional magnetic field of about 4000 A / m to the vicinity of the substrate with a permanent magnet during film formation.
[0193]

Co thus produced ₉₀ Fe _Ten Hc (hard axis direction) of film and Co ₉₀ Fe _Ten The relationship between the film thicknesses is shown in FIG. For comparison, FIG. 29 shows a direct Co film without a Cu base film on a glass substrate. ₉₀ Fe _Ten A film-formed one is also shown. The coercive force Hc was measured with a vibration magnetometer.
[0194]
As can be seen from FIG. 29, normal Co without a Cu underlayer is provided. ₉₀ Fe _Ten The film showed a high Hc of 2000 A / m or more at a film thickness of 20 nm or less. On the other hand, when a Cu base film is provided, a Co film having a thickness of 20 nm is formed. ₉₀ Fe _Ten In the film, the decrease in Hc was slight, but the Hc significantly decreased to 400 to 900 A / m at a film thickness of 10 nm or less. Thus, the glass substrate and Co ₉₀ Fe _Ten By providing a Cu base film between the film and Co, ₉₀ Fe _Ten It was found that the Hc of the film can be reduced. In particular, when the film thickness of the Cu underlayer is one atomic layer or more, the above-described effect of reducing Hc was recognized. Note that when a Co film was formed on the Cu underlayer in exactly the same manner, a decrease in Hc was not observed as in the case of the CoFe film.
[0195]
(Example 19)
A Cu base film having a thickness of 5 to 6 nm is formed on a glass substrate, and a Co base film is further formed on the Cu base film. ₉₀ Fe _Ten Film, 2 nm thick Cu intermediate layer, and Co ₉₀ Fe _Ten Films were sequentially formed. The film forming conditions for these films were the same as in Example 18.
[0196]
Hc (hard axis direction) and Co in this laminated film (Cu / CoFe / Cu / CoFe) ₉₀ Fe _Ten FIG. 30 shows the relationship between the film thicknesses. Further, in FIG. 30, as in FIG. 29, the Co base film is not directly provided on the glass substrate. ₉₀ Fe _Ten A film-formed one is also shown.
[0197]
As can be seen from FIG. 30, in the laminated film without the Cu base film, the unit Co ₉₀ Fe _Ten When the film thickness is 5 nm or more, Hc increases rapidly, but when the film thickness is 3 nm or less, Hc is 800 A / m. Thus, Hc can be reduced simply by providing a Cu intermediate layer. Furthermore, Hc can be further reduced by providing a Cu base film on this laminated film, and the unit Co ₉₀ Fe _Ten It can be seen that a low Hc of 220 to 400 A / m can be obtained when the film thickness is 7 nm or less. Therefore, Co using a Cu underlayer and a Cu intermediate layer ₉₀ Fe _Ten In the laminated film, Hc can be significantly reduced as compared with the case of Example 18.
[0198]
Cu5nm / Co ₉₀ Fe _Ten 2.2nm / Cu2nm / Co ₉₀ Fe _Ten FIG. 31 shows the magnetization curve (easy axis direction) of the laminated film of 2.2 nm. As can be seen from FIG. 31, the remanent magnetization is 90% or more even when the magnetic field is zero. ₉₀ Fe _Ten It can be seen that the magnetization of the ferromagnetic film exhibits a ferromagnetic magnetization behavior rather than antiferromagnetic.
[0199]
(Example 20)
Co ₉₀ Fe _Ten The unit film thickness of the film is set to 1.5 nm, the unit film thickness of the Cu film is set to 1.5 nm, and a (CoFe / Cu) n film is produced under the film formation conditions shown in Example 18, and the Hc and the number of laminations n are I investigated the relationship. The result is shown in FIG. In this case, Co on the glass substrate ₉₀ Fe _Ten A film, a Cu film stacked in this order, a Cu film, and a Co film ₉₀ Fe _Ten The layers stacked in the order of the films (the first layer of Cu is considered to correspond to the base film) were examined.
[0200]
As can be seen from FIG. 32, when the number of stacks is 2, Co ₉₀ Fe _Ten When the film is formed first, Hc is slightly high at 650 A / m. However, when the number of laminations is 4 to 8, Co is ₉₀ Fe _Ten Hc is as low as 100 to 300 A / m regardless of whether the film is first or the Cu film is first. This is presumably because the effect of the Cu underlayer becomes thinner as the number of laminations increases, and Hc decreases regardless of the presence or absence of the Cu underlayer (first layer Cu film). Note that the magnetization curve in this case also has a shape showing ferromagnetic coupling as in FIG.
[0201]
This laminated film has a large crystal grain size, that is, a Cu film and a Co film, based on cross-sectional transmission electron microscope observation and measurement of the half-value width of the diffraction peak of the X-ray diffraction curve. ₉₀ Fe _Ten It was found that crystals grew continuously and epitaxially at the interface with the film. Therefore, this laminated film is different from a conventional multilayer film such as Fe / C that exhibits soft magnetism by the microcrystal effect utilizing the crystal growth blocking effect at the interface between the nonmagnetic film and the ferromagnetic film, Since there is no extra resistance increase, it can be applied to a magnetoresistive film using spin-dependent scattering.
[0202]
(Example 21)
(Co ₉₀ Fe _Ten In the / Cu) n film, it is known that the magnetization of the ferromagnetic film adjacent to the Cu film is antiferromagnetically coupled or ferromagnetically coupled depending on the Cu film thickness. FIG. 33 shows (Co ₉₀ Fe _Ten (1nm) / Cu) ₁₆ The relationship between Hs (saturation magnetic field) in the hard axis direction and the film thickness of the unit Cu film is shown. When the film thickness of the Cu film is set in the vicinity of 1 nm and 2 nm, large Hs (12 to 240 kA / m) due to antiferromagnetic coupling between adjacent ferromagnetic films is exhibited. In addition, a magnetization curve representing antiferromagnetic coupling in which the remanent magnetization is greatly reduced as shown in FIG. 34 also in the easy axis direction is shown. On the other hand, at other film thicknesses, Co is similar to the magnetization curve shown in FIG. ₉₀ Fe _Ten Hs (1000 to 2000 A / m) corresponding to the induced magnetic anisotropy of the magnetic field, and the magnetization curve in the easy axis direction also showed a characteristic of having no antiferromagnetic coupling with a residual magnetization of 90% or more. .
[0203]
Further, as can be seen from FIG. 33, it can be seen that ferromagnetic coupling can be obtained by setting the film thickness to an intermediate value of, for example, about 1.5 nm. In the case of ferromagnetic coupling, since Hs is low, it is possible to increase the permeability in the difficult axis direction, which is important for magnetic sensor applications such as a magnetic head. Thus, unlike the conventional artificial lattice film exhibiting the giant magnetoresistance effect, it is desirable that the film thickness of the Cu film in this embodiment be an intermediate value that does not cause antiferromagnetic coupling.
[0204]
(Example 22)
A ferromagnetic multilayer unit 51 was formed on the substrate 50 under the same film forming conditions as in Example 18. Here, the ferromagnetic multilayer unit 51 includes a Cu film that is a non-magnetic film and a Co film that is a ferromagnetic film, as described in Examples 20 and 21. ₉₀ Fe _Ten A laminated film with a film. Next, a nonmagnetic film 52 having a thickness different from that of the nonmagnetic film in the ferromagnetic multilayer unit was formed on the ferromagnetic multilayer unit 51, and the ferromagnetic multilayer unit 51 was further formed thereon. Next, an antiferromagnetic film 53 made of FeMn, NiO, NiCoO or the like was formed thereon, and a protective film 54 was further formed thereon. The protective film 54 is formed as necessary. Finally, in order to supply a current to the edge portion, an electrode terminal 55 was formed on the protective film 54 to produce the magnetoresistive effect element shown in FIG.
[0205]
Here, by forming the ferromagnetic multilayer unit 51 and the antiferromagnetic film 53 in a unidirectional magnetic field, an exchange bias can be applied to the ferromagnetic multilayer unit 51 in direct contact with the antiferromagnetic film 53. Since the magnetization of the ferromagnetic film in the ferromagnetic multilayer unit 51 exchange-coupled to the antiferromagnetic film 53 is fixed, a CoFe single layer film having slightly lower soft magnetism may be used instead of the ferromagnetic multilayer unit 51. Good. Further, the ferro-bonded CoFe / Cu interface is not necessarily flat, and the same effect is exhibited even when a layered CoFe is mixed in the Cu film as shown in FIG.
[0206]
Ferromagnetic laminate unit 51 (Co ₉₀ Fe _Ten 1nm / Cu1.2nm) _Four Magnetization of magnetoresistive effect element using non-magnetic film 52 as a Cu film with a thickness of 2.5 nm, antiferromagnetic film 53 as a FeMn film with a thickness of 10 nm, and protective film 54 as a Cu film with a thickness of 6 nm. Curves and resistance change characteristics (the magnetic field direction is the easy axis direction) are shown in FIGS. 37 and 38, respectively. The resistance was measured by a four-terminal method.
[0207]
As can be seen from FIGS. 37 and 38, the magnetization is antiferromagnetically coupled between the two ferromagnetic multilayer units 51 at H> 800 A / m, and the two ferromagnetic multilayer units at H <500 A / m. Between 51, the magnetization is ferromagnetically coupled. That is, it can be seen that the magnetization changes from ferromagnetic coupling to antiferromagnetic coupling between H = 500 and 800 A / m. The resistance is greatly changed by a slight magnetic field region of H = 500 to 800 A / m, that is, a slight hysteresis, and the resistance change rate ΔR / R at this time is 8%.
[0208]
For comparison, Co ₉₀ Fe _Ten A magnetoresistive element having a spin valve structure shown in FIG. ₉₀ Fe _Ten 39 and 40 show the magnetization curve and resistance change characteristics of the single layer film, respectively.
[0209]
As can be seen from FIGS. 39 and 40, the magnetization curve has a larger hysteresis than the resistance change of FIG. 38, and as a result, there is a large hysteresis in the resistance change characteristic. ΔR / R is about 6.5%, which is smaller than the resistance change in FIG.
[0210]
From the above description, the magnetoresistive effect element of the spin valve structure using the ferromagnetic laminated film of the present invention has good soft magnetism, can obtain a large resistance change with a slight magnetic field, and further, inside the ferromagnetic laminated unit. Co ₉₀ Fe _Ten It can be seen that the resistance change rate is large because the / Cu interface exists.
[0211]
The embodiments of the (CoFe / Cu) n laminated film have been described in detail so far, but this spin valve structure has other ferromagnetic films (for example, NiFe, NiFeCo, Co, etc.) and other nonmagnetic films (Cu-based alloys). The same effect can be expected also in the lamination with the above. Next, in the spin valve structure in FIG. 35, the resistance change rate in the easy axis direction and Hc when the ferromagnetic multilayer unit 51 is changed to various ferromagnetic coupling multilayer films are shown in Table 5 below.
[0212]
[Table 5]

[0213]
As can be seen from Table 5, Hc can be reduced even when a ferromagnetic multilayer film other than CoFe / Cu is used, compared to a spin valve film using a single-layer magnetic film (see Table 2), and resistance equal to or higher than that. It can be seen that the rate of change can be realized.
[0214]
(Example 23)
As the ferromagnetic laminated unit 51 on the substrate side in FIG. 35, a 4 nm thick Cu underlayer and a 5 nm thick Co film are used. ₉₀ Fe _Ten And 8 nm thick Co on the ferromagnetic laminated unit 51 on the antiferromagnetic film 53 side. ₉₀ Fe _Ten FIG. 41A, FIG. 41B, and FIG. 42 show magnetization curves and resistance change characteristics when a single layer film is used, respectively.
[0215]
As can be seen from FIG. 41 (A), Hc shows a relatively large value of 800 A / m or less in the easy axis direction, but as can be seen from FIG. 41 (B), a low value of 100 A / m or less in the difficult axis direction. Indicates. Further, as can be seen from FIG. 42, the resistance change rate ΔR / R is 7.2% in the easy axis direction and 2.8% in the hard axis direction. The low rate of resistance change in the hard axis direction is considered to be insufficient for antiparallel magnetization due to ferro coupling between the two ferromagnetic layers, and the antiparallel magnetization alignment is promoted by a hard magnetic film or the like. By applying a bias magnetic field, ΔR / R comparable to that in the easy axis direction can be obtained. That is, Cu base film and Co ₉₀ Fe _Ten Both good soft magnetism and high ΔR / R can be obtained by using a laminated film.
[0216]
(Example 24)
The ferromagnetic film lamination unit 51 used in Example 22 and the nonmagnetic film 52 having a different thickness from the nonmagnetic layer in the ferromagnetic film lamination unit 51 were alternately laminated on the substrate 50 at least twice or more. Further, a protective film 54 was formed on the uppermost nonmagnetic film 52. The protective film 54 is formed as necessary. Finally, an electrode terminal 55 for supplying a current to the edge portion was formed to produce the magnetoresistive element shown in FIG.
[0217]
Ferromagnetic laminate unit 51 (Co ₉₀ Fe _Ten 1nm / Cu0.6nm) _Four FIG. 44 and FIG. 45 show the magnetization curve and resistance change characteristics in the hard axis direction of the film, the nonmagnetic layer 52 is a Cu film having a thickness of 2.2 nm, and the number of laminations is eight.
[0218]
As can be seen from FIGS. 44 and 45, the saturation magnetic field Hs has a relatively small value of 6000 A / m, and Hc has a small value of 240 A / m. At this time, the resistance change rate is 12% or less, the magnetic field at which the resistance change is saturated substantially coincides with the saturation magnetic field Hs in the magnetization curve, and the hysteresis substantially coincides with Hc of the magnetization curve. Thereby, it turns out that a large resistance change rate is shown with a slight magnetic field.
[0219]
(Example 25)
(Co) on the (110) surface of the MgO substrate 60 processed into a mirror surface state (Co ₉₀ Fe _Ten 1nm / Cu1.1nm) ₁₆ A laminated film 61 was formed. This laminated film 61 is 1 × 8 mm using a metal mask. ² Patterned into a stripe shape. Next, an electrode terminal 62 for supplying current to the edge portion was formed on the laminated film 61 to produce a magnetoresistive effect element. A Cu film having a thickness of 5.5 nm may be formed on the laminated film 61 as a protective film. In addition, the composition of the CoFe-based alloy film exhibits a large resistance change rate [Journal of the Japan Society of Applied Magnetics, 16 , 313 (1992)] and Co in terms of soft magnetic properties ₉₀ Fe _Ten It was.
[0220]
In this case, on the (110) surface of the MgO substrate 60, Co ₉₀ Fe _Ten Formed from a membrane. This is because a large resistance change of 10% or more cannot be obtained when formed from a Cu film. In FIG. 46, the wavy line shown in the laminated film 61 shows the cross section of the main growth surface. An MR sense current (Is) is passed in the direction in which the main growth surface is fluctuating.
[0221]
Here, as a film forming apparatus for forming the laminated film 61, a multi-source simultaneous sputtering apparatus was used. This sputtering apparatus uses Co ₉₀ Fe _Ten The target can be RF sputtered and the Cu target can be DC sputtered, and the film is formed by passing a substrate to which a direct current bias is applied alternately on each target. A cryopump was used as the main exhaust pump. Using this film forming apparatus, the inside of the vacuum chamber is 5 × 10 5 ^-7 After exhausting to below Torr, Ar gas was introduced into the vacuum chamber, and sputtering was performed at about 3 mTorr.
[0222]
The resistance change rate and crystal structure of the obtained magnetoresistive effect element were examined. In addition, the resistance change rate measured the resistance change of the static magnetic field direction by the four probe method. The current density at this time is 2.0 to 2.5 KA / cm. ² It was. The crystal structure was evaluated by measuring a θ-2θ scan and a rocking curve related to the main diffraction plane by the X-ray diffraction method under the following measurement conditions.
[0223]
X-ray diffraction measurement conditions
(1) θ-2θ scan
Cu-Kα, 40 kV, 200 mA
Scan width: 2θ = 2-100 °
Step width: 0.03 °
Coefficient time: 0.5 seconds
(2) Rocking curve
Cu-Kα, 40 kV, 200 mA
Scan width: 2θ = 20-60 °
Step width: 0.04 °
Coefficient time: 0.5 seconds
47A and 47B show X-ray diffraction curves by θ-2θ scanning of the laminated film of the magnetoresistive effect element. As shown in FIG. 47B, a strong diffraction peak corresponding to fcc phase (220) surface reflection can be confirmed in the vicinity of 2θ = 75 °. Thus, it can be seen from the X-ray diffraction curve that the main growth surface of the laminated film is an fcc phase (220) surface that is distorted in one direction. Note that the peak in the vicinity of 2θ = 4 ° in FIG. 47A is diffraction due to the stacking period (˜2.1 nm).
[0224]
Next, with respect to this main growth surface, rocking curves were measured from the [100] axis direction and the [110] axis direction. The results are shown in FIGS. 48 (A) and 48 (B). FIG. 48A shows a rocking curve measured from the [110] axial direction. From this, one peak can be confirmed near θ = 38 °. On the other hand, FIG. 48B shows a rocking curve from the [100] axis direction. From this, the existence of two peaks near θ = 33 ° and 41 ° can be confirmed.
[0225]
49A and 49B are conceptual diagrams of the film structure determined from the rocking curve of FIG. The wavy layer in FIG. 49A shows the fcc phase (110) plane of the main growth plane. The average crystal growth plane measured by the θ-2θ scan X-ray diffraction method is (110), but the (110) plane fluctuates in the [100] axis direction. On the other hand, the fluctuation in the [110] axial direction is extremely small. This corresponds to two peaks ([100] axial measurement) of the rocking curve shown in FIG. 48 (B) and one peak ([110] axial measurement) shown in FIG. 48 (A).
[0226]
FIG. 49B shows the in-film component distribution of the normal line of the growth surface. This in-plane anisotropy has a large in-plane distribution in the [100] axis direction and a small in the [110] axis direction due to large fluctuations in the [100] axis direction. As will be described later, the resistance change rate (ΔR / R) when the MR sense current is passed in the [110] axial direction is about 30%, whereas when the MR sense current is passed in the [100] axial direction, About 35%.
[0227]
Next, the magnetic properties of this laminated film were measured. Magnetic curves based on the results are shown in FIGS. 50 (A) and 50 (B). FIG. 50A shows a magnetization curve when an external magnetic field H is applied parallel to the [100] axis, and FIG. 50B shows a magnetization curve when an external magnetic field H is applied parallel to the [110] axis. Show. The magnetic characteristics of the magnetoresistive element were measured with a vibration magnetometer (VSM) at a maximum applied magnetic field of 1.2 MA / m. The magnetization amount M of the magnetization curve is shown by normalizing the saturation magnetization Ms.
[0228]
As can be seen from FIGS. 50A and 50B, the [100] axis is the easy axis and the [110] axis is the hard axis. At this time, the saturation magnetic field of the easy axis is about 240 kA / m, and the saturation magnetic field of the hard axis is about 960 kA / m.
[0229]
As described above, in this embodiment, a laminated film in which a ferromagnetic film and a nonmagnetic film are sequentially laminated at least once on a substrate is provided, and the direction of the sense current is in the fluctuation direction of the crystal orientation plane of the laminated film. Provided is a magnetoresistive element characterized in that the magnetoresistive element is set in a direction along the direction.
[0230]
In this embodiment, the normal line of the main crystal orientation plane of the laminated film has a component in the film plane due to fluctuation of the crystal orientation plane, and the in-plane component has anisotropy. Alternatively, the normal of the surface defect generated in the crystalline laminated film has a fluctuation in the film surface, and this fluctuation has anisotropy in the film surface. The direction in which the anisotropy is strong is a direction in which ferromagnetic atoms and nonmagnetic atoms are likely to be mixed in the atomic plane where the film is grown.
[0231]
By passing a sense current in that direction, that is, in a direction in which the anisotropy due to the in-film component becomes the largest, the probability that electrons are spin-dependently scattered increases. As a result, the magnetoresistive effect element exhibits a higher resistance change rate.
[0232]
(Example 26)
Various magnetoresistive elements having the same laminated film structure as in Example 25 were manufactured by changing the bias applied to the substrate. FIG. 51 shows the bias voltage dependence of the resistance change rate. The measurement was performed by passing a current parallel to the [100] axis and the [110] axis which are orthogonal to each other on the (110) plane of the MgO substrate. As can be seen from FIG. 51, the resistance dependency of each axis is weakly dependent on the bias, showing a value of about 35% on the [100] axis and about 30% on the [110] axis. That is, it can be seen that the [100] axis has a higher resistance change rate than the [110] axis.
[0233]
(Example 27)
Laminated film (Cu2nm / Co ₉₀ Fe _Ten 1nm) ₁₆ A magnetoresistive element was fabricated in the same manner as in Example 25 except that the film was used.
[0234]
Thus, when the film thickness of the Cu film was increased to 2 nm, the rate of change in resistance when current was passed in the [100] axis direction was about 25% and in the [110] axis direction was about 19%. . Therefore, it is understood that the direction dependency of the resistance change rate is maintained even when the thickness of the Cu film is increased. Also in this case, the rocking curve of the main growth surface (fcc phase (220) surface) has two peaks on the [100] axis as shown in FIG. 48 (B), and [110 as shown in FIG. 48 (A). ] One peak was confirmed on the axis.
[0235]
Note that the film thickness of the Cu film and Co ₉₀ Fe _Ten Even if the film thickness is changed from 0.3 nm to 10 nm, the tendency of the rocking curve does not change as described above, and the [100] axis is more fluctuating. Also, the rate of change in resistance tended to be larger on the [100] axis.
[0236]
In addition, even when the number of laminations was changed from 2 to 70 with the same configuration, the tendency of the rocking curve and the resistance change rate did not change, and a larger resistance change was obtained when the sense current was passed in the [100] axis direction.
[0237]
(Example 28)
Laminated film (Ru1nm / Co ₉₀ Fe _Ten 1nm) ₁₆ A magnetoresistive element was fabricated in the same manner as in Example 26 except that the film was used.
[0238]
ΔR / R of this magnetoresistive effect element was larger when a sense current was passed in the [100] axis direction than when a sense current was passed in the [110] axis direction. Moreover, the above-mentioned tendency was recognized even when the film thickness of the Ru film was changed.
[0239]
This phenomenon is ₉₀ Fe _Ten It was confirmed even when a Co film was used instead of the film. Further, even when Ag, Au, Pd, Pt, or Ir other than Ru was used as the material of the laminated film, a difference in ΔR / R depending on the axial direction on the (110) plane of the MgO substrate could be confirmed.
[0240]
(Example 29)
Laminate film (Cu1.1nm / Ni ₈₀ Fe ₂₀ 1.5nm) ₁₆ A magnetoresistive element was fabricated in the same manner as in Example 25 except that the film was used.
[0241]
When a sense current was passed in the [100] axial direction of the laminated film of this magnetoresistive effect element, the rate of change in resistance was 21%. On the other hand, the rate of change in resistance when a sense current was passed in the [110] axial direction was 17%. This laminated film is also made of Co. ₉₀ Fe _Ten As in the case of the / Cu laminated film, the crystal growth surface is the fcc phase (110) surface, and the rocking curve measurement shows that the growth surface fluctuates in the [100] axis direction. Ni ₈₀ Fe ₂₀ The same tendency was shown even when the film thickness and the Cu film thickness were changed from 0.5 nm to 50 nm.
[0242]
Further, even if Co, CoFe alloy, NiFe alloy, Fe, FeCr alloy or the like is used as the material of the ferromagnetic film, Cu, Au, Ag, Cr, Ru, CiNi alloy or the like is used as the material of the nonmagnetic film, It was found that a large resistance change rate is exhibited if the crystal axis direction in which the main growth surface of the laminated film fluctuates and the sense current direction are parallel.
[0243]
(Example 30)
A Co film having a thickness of 1.5 nm, a Ge film having a thickness of 50 nm, and an Au film having a thickness of 1.5 nm were formed on the (110) plane of the GaAs substrate. Further, it is shown in FIG. 53 by using the MBE method (Cu 0.9 nm / Co ₉₀ Fe _Ten 1nm) ₂₀ A laminated film was formed. In the figure, 69 indicates a Cu film, and 71 indicates Co. ₉₀ Fe _Ten The membrane is shown. Further, a 5 nm-thick Ge film was formed as a protective film on the laminated film to produce a magnetoresistive element. This laminated film exhibited fcc phase (111) plane growth. At this time, the resistance change rate was about 15% regardless of the direction of the sense current.
[0244]
Next, a magnetoresistive effect element was manufactured in the same manner as described above except that the thickness of the Au underlayer was 0.8 nm.
[0245]
When the obtained two magnetoresistive effect elements were observed with a transmission electron microscope, the Au underlayer having a thickness of 1.5 nm had almost no lattice defects and extremely good crystallinity. On the other hand, when the thickness of the Au underlayer was 0.8 nm, {111} plane orientation was exhibited, but stacking faults were observed because the {100} plane slipped in the <110> axis direction. Further, when the resistance change rate in the <211> axis and the <110> axis direction of this magnetoresistive effect element was measured, it was about 15% in the <110> axis direction and increased to 17% in the <211> direction. It was. As a result, it can be understood that the direction dependency of the sense current of the resistance change rate occurs due to the introduction of a defect having directionality.
[0246]
FIG. 53 shows an atomic arrangement diagram of the laminated film in FIG. When the {100} atomic plane is displaced in the <110> direction, the number of interfaces encountered per unit length differs depending on whether the current flows in the <211> direction or the <110> direction, and the <211> direction. It can be seen that there are many. It was found that the dependence of the number of spin-dependent interface scattering sites of conduction electrons caused by lattice defects having such directivity on the crystal axis direction also occurred in twin defects in addition to the stacking faults described above. Examples thereof will be described below.
[0247]
An Au underlayer with a thickness of 3 nm is formed on the (100) surface of the GaAs substrate, and (Co ₉₀ Fe _Ten 1nm / Cu1.1nm) ₁₆ A laminated film was formed. This laminated film exhibited fcc phase (100) plane orientation. At this time, twins were generated with the <111> axis as the central axis. FIG. 55 shows an atomic arrangement when the cross section of the laminated film is observed from the <110> direction. As can be seen from FIG. 54, it can be seen that when twins are generated around the <111> axis, an interface between Cu and Co or Fe atoms appears in the <110> direction.
[0248]
The dependence of the resistance change rate of the laminated film on the sense current direction was measured in the <110> axis and <100> axis directions. FIG. 55 shows the correlation between the twin plane and current direction of the laminated film grown on the {100} plane and the resistance change rate. As can be seen from FIG. 55, the rate of change in resistance shows 18% when the sense current flows in the <110> axis direction, and shows a value of 16% when the sense current flows in the <100> axis direction. Thus, the resistance change rate of the <110> axis that intersected the {111} plane at a large angle appeared high. On the other hand, when twins did not occur, the dependence of the resistance change rate on the sense current direction could not be confirmed.
[0249]
(Example 31)
On a glass substrate (Cu 1.1 nm / Co ₈₁ Fe ₉ Pd _Ten 1nm) ₁₆ An artificial lattice film was formed. The artificial lattice film was formed while applying a DC bias to the substrate. FIG. 56 shows the dependence (bias dependence) of the DC bias applied to the substrate by measuring the resistance change rate by changing the magnitude of the applied DC bias.
[0250]
As can be seen from FIG. 56, the resistance change rate increases as the DC bias is increased, and shows a maximum value of about 28% at a bias of −50V. Furthermore, the resistance change rate decreases when the DC bias is increased.
[0251]
When the crystallinity of various artificial lattice films produced by changing the DC bias was evaluated, the main growth surface of all the artificial lattice films was the fcc phase (111) surface growth. Here, the long-period structure reflection intensity reflected near 2θ = 4 ° reflected from the lamination period (2.1 nm) and the peak intensity of the main growth surface reflected from the fcc phase (111) plane appearing near 2θ = 44 ° FIG. 57 and FIG. 58 show the respective bias dependencies.
[0252]
As can be seen from FIG. 57, the bias dependence of the long-period structure reflection intensity shows a slight maximum of about −20 V, but it cannot be said that there is a particularly strong correlation with the bias. As can be seen from FIG. 58, the bias dependence of the fcc phase (111) surface reflection intensity also shows a slight maximum near the bias of −10 V, but it cannot be said that there is a strong correlation with the bias.
[0253]
Further, the use of the CoFe alloy system as the ferromagnetic film increases the bulk scattering of the spin-dependent scattering, and the interface structure is less sensitive than when using the Co film as the ferromagnetic film. It has been reported that when a Co-based film is used as the ferromagnetic film, the rate of change in resistance greatly depends on the film structure.
[0254]
Next, FIG. 59 shows the bias dependence of the coercive force (Hc). As can be seen from FIG. 59, good soft magnetic characteristics of 200 A / m or less are shown up to about −50V, but the coercive force starts to increase from about −60V. Therefore, by selecting the magnitude of the DC bias to be applied, the optimum conditions for the resistance change rate and the coercive force can be selected. Even when a Si substrate, a ceramic substrate, a GaAs substrate, or a Ge substrate was used instead of the glass substrate, the optimum point of resistance change rate and coercive force could be selected in the same manner.
[0255]
(Example 32)
Here, an embodiment of the present invention in which a signal magnetic field is detected by magnetization rotation of both two ferromagnetic films having spin-dependent scattering ability will be described.
[0256]
As shown in FIG. 60, a base film 81 for controlling the orientation of an antiferromagnetic film, an antiferromagnetic film 82, a ferromagnetic film 83 having a spin-dependent scattering ability, a nonmagnetic film 84, and a ferromagnetic film 85 on a substrate 80. , And an antiferromagnetic film 82 were sequentially formed. Further, an electrode terminal 86 was formed on the uppermost antiferromagnetic film 82. A protective film may be formed on the antiferromagnetic film 82 as necessary. When the antiferromagnetic film 82 is made of FeMn, the material of the base film 81 has a Cu alloy such as Cu, CuV, or CuCr, a nonmagnetic fcc phase such as Pd, or a magnetic fcc phase such as NiFe or CoFeTa. Metal is preferred. At this time, even if the magnetic material is thinner (that is, the shunt shunt is less), a good exchange bias can be applied. The antiferromagnetic film 82 is made of FeMn, NiO, PtMn or the like and has a thickness of 5 to 50 nm. The ferromagnetic films 83 and 85 are made of NiFe, Co, CoFe, NiFeCo or the like and have a thickness of 0.5 to 20 nm. The nonmagnetic film 84 is made of Cu, Au, Ag, or the like and has a thickness of 0.5 to 10 nm. Further, the antiferromagnetic film 82 does not need to be formed on the entire surface of the ferromagnetic film 85, and may be formed only on the edge portions (near the electrode terminal 86) on both sides of the ferromagnetic film 83.
[0257]
Here, at least during the formation of the ferromagnetic film 83, a static magnetic field in one direction is applied in the x direction (sense current direction) in FIG. As a result, an exchange coupling bias magnetic field is applied to the ferromagnetic film 83 in the direction of the static magnetic field. On the other hand, at least during the formation of the antiferromagnetic film 82, a static magnetic field is applied in a direction (minus x direction) that is 180 ° different from the direction of the magnetic field applied during the formation of the ferromagnetic film 83. As a result, an exchange coupling bias magnetic field is applied to the ferromagnetic film 85 in a direction different from the ferromagnetic film 83 by 180 °. As a result, the angle formed by the magnetizations of the two ferromagnetic films 83 and 85 is antiparallel when the signal magnetic field is zero. The signal magnetic field Hs is applied in the y direction in the figure.
[0258]
As a method of applying a bias magnetic field in the opposite direction to the ferromagnetic films 83 and 85 by the antiferromagnetic film 82, there is the following method. Films having different Neel temperatures are used as the two antiferromagnetic films 82, static magnetic field heat treatment is performed at temperatures higher than these Neel temperatures, and static magnetic field is generated at a temperature intermediate between the Neel temperatures of both antiferromagnetic films 82 during the temperature drop. Reverse direction 180 °. As a result, a bias magnetic field in the opposite direction can be applied to the ferromagnetic films 83 and 85.
[0259]
In this embodiment, unlike the conventional spin valve structure film, the magnetization bias of the ferromagnetic film to which the exchange bias from the antiferromagnetic film is added is utilized, so that the exchange bias magnetic field suppresses Barkhausen noise. It is desirable that the magnetic field is not so strong as to do. For example, although it varies depending on the track width of the applied head, the maximum is 5 kA / m. However, in the current spin valve structure film, it is common to use an exchange bias magnetic field by an antiferromagnetic film made of FeMn. In this case, if a FeMn film and a ferromagnetic film such as a NiFe film are directly laminated, An exchange bias of 10 kA / m or more occurs. In order to reduce the exchange bias, a method for inserting an exchange bias adjusting film, for example, a ferromagnetic film or a nonmagnetic film having a low saturation magnetization between the antiferromagnetic film and the ferromagnetic film, as shown in FIG. As described above, there is a method in which the nonmagnetic films 87 and 88 are interposed in the ferromagnetic films 83 and 85, that is, the ferromagnetic films 83 and 85 are separated into 83a and 83b, 85a and 85b, respectively.
[0260]
In the method of interposing a nonmagnetic film in the ferromagnetic film, a strong exchange bias is applied to the ferromagnetic films 83a and 85a on the side in contact with the antiferromagnetic film 82, but the ferromagnetic on the side not in contact with the antiferromagnetic film 82. A weak exchange bias is applied to the films 83b and 85b. The magnitude of the exchange bias to the ferromagnetic films 83b and 85b on the side not in contact with the antiferromagnetic film 82 can be reduced depending on the material type and the film thickness of the nonmagnetic films 87 and 88.
[0261]
Here, the angle formed by the magnetizations of the ferromagnetic films 83a and 83b and the angle formed by the magnetizations of the ferromagnetic films 85a and 85b change from a ferromagnetic arrangement to an antiferromagnetic arrangement by the magnetization rotation caused by the signal magnetic field. However, the angle formed by the magnetizations of the ferromagnetic films 83b and 85b at the center of the film changes from an antiferromagnetic arrangement to a ferromagnetic arrangement. Therefore, the former and the latter spin-dependent scattering are canceled out. Therefore, it is desirable that the ferromagnetic films 83a and 85a and the nonmagnetic films 87 and 88 have a high resistance and no spin-dependent scattering ability. Further, the thickness of the ferromagnetic films 83a and 85a on the side in contact with the antiferromagnetic film 82 is desirably smaller than the thickness of the ferromagnetic films 83b and 85b on the side not in contact with the antiferromagnetic film 82.
[0262]
By doing so, the magnetization directions of the ferromagnetic films 83 and 85 can be made antiparallel with a magnetic field of zero. As a result, first, even when a signal magnetic field is applied in the difficult axis direction (y direction in the figure) suitable for the magnetic head, the angle between the magnetizations of the two ferromagnetic films is 0 to 0 due to the magnetization rotation of the two ferromagnetic films. A state of changing up to 180 ° can be realized, and a high resistance change rate similar to that in the easy axis direction can be realized. Second, since a bias magnetic field is applied to the two ferromagnetic films, the domain walls can be eliminated from both ferromagnetic films, and Barkhausen noise can be suppressed. Third, the method in which the sense current and the signal magnetic field intersect at the same time combines the normal magnetoresistance effect and the resistance change due to spin-dependent scattering, which are remarkable when using a NiFe film or the like that has been canceled out in the conventional spin valve structure. And an increase in ΔR / R can be expected.
[0263]
(Example 33)
In Example 32, a method was shown in which two antiferromagnetic films were used to make the magnetizations of both ferromagnetic films antiparallel. However, it is not always necessary to apply a bias magnetic field only with an antiferromagnetic film, and a magnetic field leaking from a hard magnetic film or a demagnetizing field generated when processed into a fine shape may be used. Next, an example will be described.
[0264]
As can be seen from FIG. 62, a ferromagnetic film 91, a nonmagnetic film 92, and a ferromagnetic film 93 having spin-dependent scattering ability were formed on a substrate 90. The film thicknesses of the ferromagnetic films 91 and 93 and the nonmagnetic film 92 were the same as in Example 32. An antiferromagnetic film 94 having a thickness of 2 to 50 nm was formed thereon, and an exchange bias was applied to the ferromagnetic film 93. Further, a hard magnetic film 95 made of CoPt and CoNi having a thickness of 10 to 50 nm was formed thereon. An electrode terminal 96 was formed on the hard magnetic film 95. All the films were formed in a static magnetic field (x direction in the figure).
[0265]
Next, a hard magnetic film 95 was magnetized in the x direction by applying a magnetic field of 400 to 800 kA / m in the same direction as the exchange bias magnetic field direction by the antiferromagnetic film 94. As a result, a bias magnetic field was applied to the ferromagnetic film 91 in the minus x direction by the leakage magnetic field from the edge portion of the hard magnetic film 95, and the magnetizations of the ferromagnetic films 91 and 93 became antiparallel. A bias magnetic field from the hard magnetic film 95 is also applied to the ferromagnetic film 93. By setting the exchange bias force so that the exchange bias magnetic field from the antiferromagnetic film 94 is stronger, the above-described antiparallel characteristics are obtained. A magnetized state can be realized. The hard magnetic film 95 and the antiferromagnetic film 94 do not need to be formed on the entire surface of the ferromagnetic film 93, and may be formed only on the edge portion (near the electrode terminal 96) of the ferromagnetic film 93.
[0266]
In FIG. 62, a ferromagnetic film close to soft magnetism can be used instead of the hard magnetic film. In this case, the ferromagnetic film close to soft magnetism needs to be laminated so that an exchange bias is applied from the antiferromagnetic film 94. When an exchange bias is applied to the ferromagnetic film 95, the magnetization of the ferromagnetic film 95 can be fixed in one direction, so that a stable magnetostatic coupling bias magnetic field is applied to the ferromagnetic film 91 even when an external magnetic field such as a signal magnetic field is applied. By processing into a fine pattern shape indispensable for the resistance effect, it can be applied in a direction different from the exchange bias magnetic field from the antiferromagnetic film 94 applied to the ferromagnetic film 93 by 180 °. At this time, a bias magnetic field having a desired strength can be applied to the ferromagnetic film 91 by adjusting the film thickness and saturation magnetization of the ferromagnetic film 95.
[0267]
Further, by adjusting the resistivity and film thickness of the ferromagnetic film 95, a desired shunt diversion operating point bias can be applied. Here, the ferromagnetic film 95 has the characteristics required for exchange coupling with the antiferromagnetic film 94 (similar in crystal structure and lattice constant to the antiferromagnetic film 94 for epitaxial growth. It is difficult to achieve both a crystalline ferromagnetic film, such as a NiFe film, a CoFe film, a CoFeTa film, and a CoFePd film, and characteristics required for a magnetostatic coupling bias and an operating point bias (the above crystallinity). The resistivity of the film is too low). Therefore, the ferromagnetic film 95 includes an exchange coupling magnetic film (NiFe, CoFe ferromagnetic film, etc.) in contact with the antiferromagnetic film 94 and a biasing ferromagnetic film (Co amorphous film, FeTaN, etc.). It is desirable to have a two-layer structure in which a crystalline film or a carbonized microcrystalline film such as FeZrC) is ferromagnetically exchange coupled at the interface.
[0268]
In the structure shown in FIG. 62, since the sense current from the electrode terminal 96 flows through the hard magnetic film 95, ΔR / R is unavoidably reduced to some extent. This problem can be solved by the structure shown in FIGS.
[0269]
That is, as shown in FIG. 63, the antiferromagnetic film 94 is formed on the substrate 90 as in FIG. 62, and then the hard magnetic film 95 is formed in the vicinity of both sides of the antiferromagnetic film 94. Electrode terminals 96 are formed on the inside at intervals corresponding to the track width. As a result, the sense current can be prevented from flowing through the hard magnetic film 95, and the decrease in ΔR / R can be suppressed.
[0270]
On the other hand, as shown in FIG. 64, a hard magnetic film 95 is first formed on a substrate 90, and a ferromagnetic film 91, a nonmagnetic film 92, a ferromagnetic film 93, and an anti-strength are formed thereon via an insulating film 97. A magnetic film 94 is sequentially formed, and an electrode terminal 96 is further formed. At this time, a static magnetic field is applied during film formation, and a predetermined exchange bias magnetic field is applied from the antiferromagnetic film 94 to the ferromagnetic film 93. After the film formation, the hard magnetic film 95 is magnetized in the same direction as the exchange bias direction. Even in this method, a bias magnetic field in the opposite direction can be applied to the ferromagnetic films 91 and 93, and current can be prevented from flowing through the hard magnetic film 95. The insulating film 97 also has an effect of preventing an excessive bias magnetic field from being applied due to exchange coupling between the hard magnetic film 95 and the ferromagnetic film 91.
[0271]
As shown in FIG. 65, a ferromagnetic film 91, a nonmagnetic film 92, a ferromagnetic film 93, and an antiferromagnetic film 94 are sequentially formed on a substrate 90. Next, the laminated film is finely processed into a predetermined shape. This fine processing is performed by ion milling or the like by forming a mask using a resist or the like. Thereafter, a hard magnetic film 95 is formed on the side of the ferromagnetic film 91 by the lift-off method using the remaining mask. Finally, the hard magnetic film 95 is magnetized in the direction opposite to the exchange bias applied to the ferromagnetic film 93. Even in this method, a bias magnetic field in the opposite direction can be applied to the ferromagnetic films 91 and 93, and current can be prevented from flowing through the hard magnetic film 95.
[0272]
(Example 34)
In the spin valve structure shown in FIG. 61, a 5 nm thick Cu underlayer containing 1 at% Cr on a glass substrate 80, a 15 nm thick FeMn film as an antiferromagnetic film 82, and a 1 nm thick ferromagnetic film 83a. Ni ₈₀ Fe ₂₀ A non-magnetic film 87, a 1.5 nm thick Cu film containing 1 at% Cr, and a ferromagnetic film 83b, a 6 nm thick Ni film. ₈₀ Fe ₂₀ Film, Cu film with a thickness of 2.5 nm as the non-magnetic film 84, Ni film with a thickness of 6 nm as the ferromagnetic film 85 b ₈₀ Fe ₂₀ A film, a non-magnetic film 87 containing 1 at% Cr and a 1.5 nm thick Cu film, and a ferromagnetic film 85 a Ni having a thickness of 1 nm ₈₀ Fe ₂₀ A 15 nm thick FeMn film was sequentially formed as the film and the antiferromagnetic film 82.
[0273]
These films were formed in a lump without breaking the vacuum by a bipolar sputtering method in a static magnetic field using a permanent magnet. The permanent magnet is not integrally attached to the substrate holder. At this time, the preliminary exhaust pressure 1 × 10 ^-Four The pressure is less than Pa and the Ar gas pressure is 0.4 Pa. After the formation of the ferromagnetic film 83 is completed, the substrate holder is rotated 180 ° to change the direction of the bias magnetic field (about 4000 A / m) by the permanent magnet to 180 °. Inverted. In this way, a laminated film having a spin valve structure capable of realizing an antiparallel state of magnetization of both ferromagnetic films with a signal magnetic field of 0 was produced.
[0274]
The resistance of the obtained laminated film was measured by the 4-terminal method. Specifically, a constant current of 1 mA was applied in the easy axis direction of the ferromagnetic films 83 and 85, and the voltage between 4 mm was measured with the width of the film in the difficult axis direction being 1 mm. A magnetic field was applied in the direction of the hard axis of the ferromagnetic films 83 and 85 by a Helmholtz coil. As a result, the obtained resistance-magnetic field characteristics are shown in FIG.
[0275]
In FIG. 66, the resistance is shown by standardizing the value at the maximum magnetic field (16 kA / m) to 1. In the magnetic field 0, the magnetizations of the ferromagnetic films 83 and 85 are in an antiparallel state, so that the resistance has a maximum value. When a magnetic field is applied, the resistance rapidly decreases. In particular, the resistance shows a substantially constant value in a magnetic field of 2000 A / m or more. It can be seen that a resistance change rate of about 3.8% or less occurs in a slight magnetic field range of 2000 A / m or less. Further, almost no hysteresis or noise is observed in this resistance-magnetic field characteristic. That is, when this laminated film having a spin valve structure is used, a magnetic head with extremely high sensitivity and less noise can be obtained.
[0276]
Further, the spin valve magnetoresistive effect element shown in FIG. 60 was manufactured, and the relationship between the thickness of the nonmagnetic layer 84 (Cu) and the resistance change rate was examined. The results are shown in Table 6 below. A NiFe film having a thickness of 5 nm was used as the base film, a NiFe film having a thickness of 8 nm was used as the ferromagnetic films 83 and 85, and a FeMn film having a thickness of 10 nm was used as the antiferromagnetic film 82.
[0277]
[Table 6]

[0278]
As can be seen from Table 6, the resistance change rate increased abruptly when the Cu thickness was reduced, and a high resistance change rate of 9% was obtained when the Cu thickness was 1.2 nm. This is because a relatively large antiparallel bias magnetic field of 50 kA / m is applied to each of the ferromagnetic film 83 and the ferromagnetic film 85, so that the antiferromagnetic magnetization stable even if the thickness of the nonmagnetic film 84 is reduced. This is because an array can be realized. When the thickness of the nonmagnetic layer (Cu) is reduced to less than 2 nm, unlike the conventional spin-valve magnetoresistive effect element in which the antiparallel magnetization arrangement collapses and the resistance change rate drastically decreases, both the ferromagnetic films 83 and 84 are opposite. By applying a bias magnetic field in the direction and reducing the thickness of the nonmagnetic film 84, the resistance change rate can be greatly increased.
[0279]
(Example 35)
Next, a case where the number of ferromagnetic films having spin-dependent scattering ability is increased to three or more layers will be described.
[0280]
As shown in FIG. 67, a base film 101 for controlling the orientation of the antiferromagnetic film 102 on the substrate 100, an antiferromagnetic film 102 having a thickness of 5 to 50 nm made of FeMn, NiO, PtMn, etc., CoFe, Co 1 to 20 nm thick ferromagnetic film 103 made of NiFe or the like, 1 to 10 nm thick nonmagnetic film 104 made of Cu, Au or the like, 1 to 20 nm thick ferromagnetic film 105, 1 to 10 nm thick A nonmagnetic film 106, a ferromagnetic film 107 having a thickness of 1 to 20 nm, and an antiferromagnetic film 108 having a thickness of 5 to 50 nm were formed. Here, the film thicknesses of the ferromagnetic films 103, 105, and 107 may all be equal or different. Furthermore, a protective film was formed thereon as necessary to form electrode terminals 109. The film formation was performed in a static magnetic field.
[0281]
An exchange bias was applied in one direction (x direction in the figure) from the antiferromagnetic films 102 and 108 to the ferromagnetic films 103 and 107, respectively. As a result, only the intermediate ferromagnetic film 105 has a high magnetic permeability, and the ferromagnetic films 103 and 107 have a low magnetic permeability, that is, a fixed magnetization. For fixing the magnetization, a hard magnetic film 95 as shown in FIG. 63 may be used instead of the antiferromagnetic film. Incidentally, Co or CoFe having a high resistance change rate is used as the material of the ferromagnetic films 103 and 107 in contact with the antiferromagnetic films 102 and 108, but the resistance change rate is used as the material of the intermediate ferromagnetic film 105. By using NiFe which is not so high but has good soft magnetism, a high resistance change rate can be realized in a low magnetic field.
[0282]
With such a configuration, the magnetization rotation of the intermediate ferromagnetic film 105 easily occurs in a low magnetic field, and the number of interfaces through the nonmagnetic layer increases twice as compared with the conventional spin valve structure film. It is possible to realize a resistance change rate exceeding that of a conventional spin valve structure film in a low magnetic field. In addition, since the ferromagnetic film whose magnetization is rotated by the signal magnetic field is located at the center of the laminated film, the ferromagnetic film is hardly disturbed by the sense current magnetic field, and stable signal detection is possible. If a hard magnetic film or a bias method using a demagnetizing field as described in Example 33 is used in combination, the angle formed by the magnetizations of the ferromagnetic films 103 and 107 and the intermediate ferromagnetic film 105 is antiparallel with a signal magnetic field of 0. Can be. As a result, a magnetoresistive effect element with higher sensitivity and lower noise can be obtained by the various effects described in the embodiment 32.
[0283]
(Example 36)
FIG. 68 shows a laminated film in which the number of ferromagnetic films having spin-dependent scattering capability is increased to four.
[0284]
On the substrate 100, an antiferromagnetic film 111, four layers of ferromagnetic films 112, 114, 116, and 118, and an antiferromagnetic film 119, which are stacked via nonmagnetic layers 113, 115, and 117, are sequentially formed, and sensed. An electrode terminal 109 was formed on the electrode terminal 109 so that current flowed in the same direction as the signal magnetic field. If necessary, a base film for orientation control is formed under the antiferromagnetic film 111, and a protective film is formed over the antiferromagnetic film 119. The material and film thickness of each film were the same as those shown in FIG.
[0285]
At least during the film formation of the ferromagnetic film 112, a static magnetic field is applied in the x direction (track width direction) in the figure, while at the same time during the subsequent film formation, the direction of the static magnetic field is reversed by 180 ° to at least the antiferromagnetic film 119 During film formation, a static magnetic field was applied in the minus x direction in the figure. Due to the static magnetic field during film formation, magnetization is fixed by an exchange bias magnetic field in the ferromagnetic film 112 in the x direction and in the negative x direction in the ferromagnetic film 118. Further, in this configuration, if the track width is narrow, the widths of the ferromagnetic films 112, 114, 116, and 118 are similarly narrowed, and thus a strong demagnetizing field is generated in that direction. Due to this demagnetizing field, the magnetizations of the intermediate ferromagnetic films 114 and 116 not in contact with the antiferromagnetic film become antiparallel to the magnetizations of the ferromagnetic films 112 and 118, respectively. That is, in the signal magnetic field 0, adjacent magnetizations of the four layers of ferromagnetic films are antiparallel to each other.
[0286]
When the demagnetizing field on the intermediate ferromagnetic films 114 and 116 is insufficient, the magnetic field generated by the sense current is in the minus x direction in the ferromagnetic films 112 and 114, and in the x direction in the ferromagnetic films 116 and 118. It is desirable to apply a sense current in the y direction in the figure so as to be applied to. Here, if the exchange bias magnetic field from the antiferromagnetic film is set to be larger than the sense current magnetic field, the magnetization of the ferromagnetic films 112 and 118 is not disturbed by the current magnetic field, and the exchange from the antiferromagnetic film is performed. Can be fixed in the bias direction.
[0287]
With this configuration, the magnetization directions of the four layers of ferromagnetic films can be arranged antiferromagnetically with a signal magnetic field of zero. Therefore, ΔR / R increases corresponding to the increase in the number of interfaces. Further, since the magnetization of each layer can be rotated by applying a slight signal magnetic field, a magnetoresistive effect element using spin-sensitive scattering with high sensitivity can be realized.
[0288]
(Example 37)
Next, a case where the magnetization of a part of the ferromagnetic film having spin-dependent scattering ability is fixed and the magnetization of the remaining ferromagnetic film is arranged in a direction different from the signal magnetic field direction by the signal magnetic field 0 will be described.
[0289]
FIG. 69 shows a stacked film in which the directions of the sense current and the signal magnetic field are orthogonal. On the substrate 120, a laminated film of ferromagnetic films 121 and 123 having a spin-dependent scattering ability with a nonmagnetic film 122 interposed, and an antiferromagnetic film 124 were sequentially formed. The material and thickness of each film were the same as those shown in FIG. If necessary, an electrode terminal 125 was formed after forming a protective film on the antiferromagnetic film 124.
[0290]
Here, at least during the formation of the ferromagnetic film 121, a static magnetic field is applied in the direction of the bisector of the x-axis and the y-axis in the figure, while at least during the formation of the antiferromagnetic film 124. The direction of the static magnetic field was applied by rotating 45 degrees with respect to the former direction (y direction in the figure). As a result, the magnetization of the ferromagnetic film 121 was applied in the x direction of the static magnetic field, and the magnetization of the ferromagnetic film 123 was fixed in the signal magnetic field direction by the bias magnetic field from the antiferromagnetic film 124. According to such a configuration, when the signal magnetic field is zero, the angle between the magnetizations of the two ferromagnetic films is 45 °, and when the signal magnetic field is applied to the magnetization fixed direction of the ferromagnetic film 123, the magnetization directions of the two ferromagnetic films are changed. The resistance decreases due to the ferromagnetic arrangement, and conversely, when a signal magnetic field is applied in a direction 180 ° different from the magnetization fixed direction, the resistance increases because the magnetization directions of both ferromagnetic films become an antiferromagnetic arrangement. To do. Therefore, the operating point bias necessary for the conventional magnetoresistive element to realize the linear response is not necessary. In this method, due to the ferromagnetic coupling between the ferromagnetic films 121 and 123, the magnetization of the ferromagnetic film 121 tends to tilt in the y direction when the signal magnetic field is 0, and the reproduction signal is easily distorted when a large signal magnetic field is applied. Tend. This is because the magnetic field generated by the sense current is applied to the ferromagnetic film 121 in a direction different from this ferromagnetic coupling direction by 180 °, that is, the magnetic field due to this ferromagnetic coupling cancels out the current magnetic field. This can be avoided by determining the direction in which the sense current flows.
[0291]
However, when a film having an anisotropic magnetoresistance effect is used for the ferromagnetic films 121 and 123, the magnetization M of the ferromagnetic film 121 is changed to the magnetization M of the ferromagnetic film 123 by the magnetic field due to the ferromagnetic coupling. When tilted in the direction, the magnetic anisotropy and the resistance change due to the spin heterogeneous scattering are superposed (because the current direction is the x direction), there is an advantage that an improvement in sensitivity can be expected. Actually, it is necessary to adjust the magnetization direction of the ferromagnetic film 121 by means such as a current direction according to the situation in which the magnetoresistive effect element is used.
[0292]
By the way, in Example 37, it is necessary to apply a longitudinal bias magnetic field (bias magnetic field in the bisecting direction of the x-axis and y-axis in the figure) necessary for Barkhausen noise suppression. For this purpose, an antiferromagnetic film as shown in Example 32 is arranged on the substrate side of the ferromagnetic film 121 and exchange coupled. Alternatively, as shown in FIG. 70A, soft magnetism is good to some extent on the antiferromagnetic film 124 (Hc is an exchange bias magnetic field H). _UA (Smaller) ferromagnetic film 126 is laminated, and at least during the lamination of the ferromagnetic film 126, the direction of the bias magnetic field during film formation is reversed by approximately 135 °, and the exchange bias magnetic field from the ferromagnetic film 126 is made ferromagnetic. There is a method of adding to the film 121. In this case, since the film which is a spin-dependent scattering unit also serves as an underlayer, an exchange bias can be easily applied to the ferromagnetic film 126 formed on the antiferromagnetic film 124. As a result, since the longitudinal bias magnetic field can be applied to the ferromagnetic film 121 by the magnetostatic coupling magnetic field (demagnetizing field) generated when the pattern is actually processed into a fine pattern suitable for the reproducing head, Barkhausen noise can be suppressed. .
[0293]
In the embodiment of FIG. 70 (A), the exchange bias direction is different on both sides of the antiferromagnetic film 124, so the bias magnetic field direction may become uneasy. As shown in FIG. 70B, this is because the antiferromagnetic film 124 is antiferromagnetic through an extremely thin intermediate film 124b (fcc phase film such as Cu) that weakens the magnetic coupling but does not inhibit crystal growth. This can be avoided by separating the membranes 124a and 124c. At this time, as described in the embodiment 32, the antiferromagnetic films 124a and 124c are preferably made of materials having different nail points or blocking temperatures in order to control the exchange bias magnetic field direction by heat treatment. Further, if the ferromagnetic film 126 is thick and Bs is not high, a desired longitudinal bias magnetic field cannot be applied to the ferromagnetic film 121. However, at this time, a sense current is shunted to the ferromagnetic film 126, so the resistivity of the ferromagnetic film is High is desirable. Specifically, it is desirable to use a Co-based or Fe-based amorphous film or a nitrided or carbonized microcrystalline film. However, since such a film is difficult to exchange-couple with an antiferromagnetic film such as FeMn, an extremely thin ferromagnetic film 124b such as NiFe or CoFeTa is laminated on a portion in contact with the antiferromagnetic film 124a. It is desirable to stack a high resistance amorphous high Bs ferromagnetic film 126a thereon so as to be ferromagnetically exchange coupled.
[0294]
(Example 38)
FIG. 70C shows a stacked film in which the directions of the sense current and the signal magnetic field are parallel. The configuration is the same as that of FIG. 69 except that the direction in which the sense current flows is different, the magnetization of the ferromagnetic film 121 is applied in the x direction in the drawing, and the longitudinal direction of the film is rotated by 90 °. In this configuration, when the signal magnetic field is zero, the angle between the magnetizations of the two ferromagnetic films is 90 °. When the signal magnetic field is applied in the magnetization fixing direction of the ferromagnetic film 123, the magnetizations of the two ferromagnetic films are arranged in a ferromagnetic arrangement. Therefore, the resistance decreases, and conversely, when a signal magnetic field is applied in a direction 180 ° different from the magnetization fixed direction, the magnetization of both ferromagnetic films becomes an antiferromagnetic arrangement, and the resistance increases. Therefore, the operating point bias becomes unnecessary. In this configuration, the current magnetic field due to the sense current is in the easy axis direction of the ferromagnetic film 121, and this magnetic field has an effect of suppressing Barkhausen noise.
[0295]
Furthermore, in Example 38, it is added that the magnetization of the ferromagnetic film 121 tends to tilt in the y direction because of the ferro-coupling magnetic field that is likely to be generated from the ferromagnetic film 123. As described in detail in Example 37, this ferromagnetic coupling magnetic field has an advantage of superimposing an anisotropic magnetoresistance effect, although the signal magnetic field dynamic range is reduced. In addition, since the current magnetic field is applied to the ferromagnetic film 121, the easy axis of the ferromagnetic film 121 is not necessarily in the x direction.
[0296]
When the Barkhausen noise suppression effect is insufficient, the magnetization pinned direction of the ferromagnetic film 123 is removed from the signal magnetic field direction, and a magnetostatic coupling magnetic field is generated in the x direction in the figure to generate a stronger Barkhausen noise suppression magnetic field. Can be granted.
[0297]
(Example 39)
FIG. 71 shows a laminated film in the case where the ferromagnetic film having the spin-dependent scattering ability has three layers. FIG. 71 shows a case where the sense current and the signal magnetic field are orthogonal to each other. On the substrate 130, a laminated film of ferromagnetic films 132, 134, and 136 having spin-dependent scattering ability with an antiferromagnetic film 131 and nonmagnetic films 133 and 135 interposed in a static magnetic field, and an antiferromagnetic film 137 are sequentially formed. Formed. An electrode terminal 138 was formed thereon.
[0298]
Here, the direction of the static magnetic field is at least the same direction during the formation of the ferromagnetic film 132 and the antiferromagnetic film 137 (the y direction in the figure), and has an angle of 45 ° with the ferromagnetic film 134 during the film formation. The direction formed (the bisector direction of the x-axis and y-axis in the figure). As a result, the magnetizations of the ferromagnetic films 132 and 136 are fixed in the y direction in the figure, the magnetization of the ferromagnetic film 134 maintains a high magnetic permeability, and the magnetic field 0 is near the bisector of the x axis and the y axis in the figure. Suitable for. Therefore, even in this configuration, when the magnetic field is zero, the angle between the magnetizations of the two ferromagnetic films is approximately 45 °, and when the signal magnetic field is applied to the magnetization fixed direction of the ferromagnetic film 136, the magnetization directions of the two ferromagnetic films are ferromagnetic. When the signal magnetic field is applied in a direction 180 ° different from the magnetization fixed direction, the resistance increases because the magnetization directions of the two ferromagnetic films are antiferromagnetic. That is, no operating point bias is required. In this configuration, the number of interfaces is doubled, so the sensitivity is improved.
[0299]
(Example 40)
The resistance-magnetic field characteristics of the laminated film of the magnetoresistive effect element of the method shown in Example 38 will be described.
[0300]
In FIG. 70C, a sapphire C-plane substrate is used as the substrate 120, a 5 nm thick Pd underlayer film is used as the ferromagnetic film 121, and a 6 nm thick Co film is used. ₉₀ Fe _Ten A 3 nm thick Cu film is used as the nonmagnetic film 122, and a 4 nm thick Co film is used as the ferromagnetic film 123. ₉₀ Fe _Ten A 15 nm thick FeMn film was used as the antiferromagnetic film 124, and a 5 nm thick Pd film was formed thereon as a protective film.
[0301]
This laminated film was formed in a lump while keeping a vacuum by a bipolar sputtering method. During film formation, a static magnetic field is applied by a permanent magnet, and after the film formation of the ferromagnetic film 121 is completed, the direction of the static magnetic field is reversed by 90 °, and the angle formed by the easy axes of the ferromagnetic films 121 and 123 Was 90 °. Sputtering preliminary exhaust is 1 × 10 ^-Four Pa or less and the sputtering gas pressure were 0.4 Pa.
[0302]
The resistance-magnetic field characteristics of this laminated film were measured in the same manner as in Example 33. FIG. 72 shows resistance-magnetic field characteristics in the hard axis direction. In FIG. 72, the resistance in the ferromagnetic magnetization arrangement is normalized as 1. As can be seen from FIG. 72, a change in magnetic field of resistance with good linearity can be obtained when the signal magnetic field is zero. This shows that no operating point bias is required.
[0303]
(Example 41)
Here, two or more different ferromagnetic films or antiferromagnetic films are laminated on both ferromagnetic films of a spin-dependent scattering unit comprising a ferromagnetic film / nonmagnetic film / ferromagnetic film, and both biases generated at that time are generated. An example of a magnetoresistive element in which magnetic fields are substantially orthogonal will be shown.
[0304]
73 shows a hard ferromagnetic film such as CoPt, a high-Hk ferromagnetic film having a uniaxial magnetic anisotropy magnetic field Hk larger than that of the spin-dependent scattering unit (for example, Hk to 5 kA / m). A first bias film 121a for applying a bias magnetic field made of an antiferromagnetic film such as a CoFeRe film) or NiO, a spin-dependent scattering unit (ferromagnetic film 121, nonmagnetic film 122, ferromagnetic film 123), FeMn 2 shows a multilayer film in which a second bias film 124 for applying a bias magnetic field made of an antiferromagnetic film or the like is sequentially stacked. The bias magnetic field generated from the multilayer first bias film 121a is mainly applied to the ferromagnetic film 121 by exchange coupling through the laminated interface. On the other hand, the bias magnetic field generated from the second bias film 124 is mainly applied to the ferromagnetic film 123 by exchange coupling through the stacked interface. The first and second bias magnetic fields are applied so as to satisfy a directional relationship that is substantially orthogonal. Further, the second bias magnetic field is set to a strong value such that the magnetization of the ferromagnetic film 123 cannot substantially move due to the signal magnetic field (preferably 10 kA / m or more).
[0305]
On the other hand, the first bias magnetic field strength is a magnetic field that can rotate the magnetization of the ferromagnetic film 121 by the signal magnetic field and suppress Barkhausen noise. Specifically, when an antiferromagnetic film is used for the first bias film, it is desirable that the bias magnetic fields of the bias film 121a and the ferromagnetic film 121 be 5 kA / m or less. When a ferromagnetic film is used as the first bias film, the magnetization direction of the bias film 121a is held in a fixed direction by some means to form a single magnetic domain, and the bias film 121a and the ferromagnetic film 121 are strongly exchanged. When integrated, the bias magnetic film 121a and the ferromagnetic film 121 can be rotated in the same manner by the signal magnetic field, and the ferromagnetic film 121a has a single magnetic domain, so that the ferromagnetic film 121 also becomes a single magnetic domain and Barkhausen noise can be removed. Alternatively, for example, there is a method in which another layer is inserted in the interface to weaken the exchange coupling between the bias film 121a and the ferromagnetic film 121 to 5 kA / m or less. In this case, since only the ferromagnetic film 121 is magnetized and rotated by the signal magnetic field, it is preferable to suppress the permeability of the bias film 121a to make the magnetization difficult to move. As this magnetic permeability suppression means, there is an improvement in Hk, an improvement in coercive force, or a unidirectional bias magnetic field applied to the bias film 121a by any means.
[0306]
Here, as means for making the ferromagnetic film 121a into a single magnetic domain, as shown in FIG. 74, the bias film 121a is made longer than the spin valve unit, and a new antiferromagnetic film or hard disk is formed at the edge of the bias film 121a. The film 121b can be stacked.
[0307]
When the magnetoresistive effect element having the above configuration is manufactured, the magnetization direction of the ferromagnetic film 123 is fixed and the magnetization of the ferromagnetic film 121 changes according to the signal magnetic field, so that the signal magnetic field is the same as in the embodiment shown in FIG. A high-sensitivity magnetoresistive element with good linearity can be obtained at ˜0, and the domain wall of the ferromagnetic film 121 for detecting the signal magnetic field can be removed, so that a signal magnetic field with high sensitivity and no noise is required without operating point bias. Playback is possible.
[0308]
Here, it is desirable to apply the easy axis direction of the ferromagnetic film 121 to a direction orthogonal to the bias magnetic field direction, particularly when a Co-based ferromagnetic film having a large magnetic anisotropy is used for the 121. Then, since the saturation magnetic field corresponding to the anisotropic magnetic field and the bias magnetic field can be canceled out, Hs can be greatly reduced, so that the gradient of the saturation magnetic field-resistance characteristic shown in FIG. Compared with the case where the easy axis of magnetization of the ferromagnetic film 121 is in the same direction, it is possible to detect a signal magnetic field with higher sensitivity. In order to change the direction of the bias magnetic field and the easy axis of the ferromagnetic film, there is a method of changing the magnetic field application direction during the formation of the bias film 121 a and the direction of magnetic field application during the formation of the ferromagnetic film 121.
[0309]
(Example 42)
As shown in FIG. 75, on the support substrate 140, a 20 nm thick Cr underlayer 141 for controlling the orientation of the high coercive force film, a 8 nm thick high coercive force film 142, a thickness made of Cu, and the like. A non-magnetic film 143 having a thickness of 3 nm and a ferromagnetic film 144 made of NiFe or the like having a thickness of 4.6 nm are sequentially formed, and an electrode terminal 145 is further formed thereon to manufacture a magnetoresistive effect element having a spin valve structure. did. The laminated film was formed by ultra-high vacuum E gun deposition. The substrate temperature at this time is about 100 ° C., and the inside of the vacuum chamber is 1 × 10 ^-8 Exhaust to Pa or less.
[0310]
The X-ray diffraction pattern of the Co / Cr film when the substrate temperature was about 100 ° C. was examined. The result is shown in FIG. As shown in FIG. 76, in this film, Cr (200) was highly oriented, and in the Co film using this Cr film as a base film, (110) was also highly oriented. The rocking curve half-width of the Co (110) peak was about 3 °.
[0311]
Next, FIG. 77 shows the RH curve in the hard axis direction of the laminated film having the NiFe / Cu / Co / Cr / substrate structure shown in FIG. 75 formed at a substrate temperature of about 100 ° C. The RH curve was created based on a value measured by a four-terminal method after processing the laminated film into a 2 mm × 6 μm pattern using a normal resist process and ion milling. At this time, the easy axis was the pattern longitudinal direction, and the magnetic field was applied in the pattern width direction.
[0312]
As shown in FIG. 77, when the applied magnetic field is ± 80 Oe, the resistance change rate was about 6.5%, and the saturation magnetic field was about 3.6 kA / m.
[0313]
In this structure, since the Hc of the high coercive force film is about 8 kA / m, there is no problem when the magnetic field from the medium is less than 8 kA / m, but the structure between the head and the medium is close, that is, the magnetic field from the medium. Is not suitable for a structure in which is 8 kA / m or more. Therefore, a laminated film was formed in a magnetic field of about 8 kA / m with the same structure and film thickness as in FIG.
[0314]
The X-ray diffraction pattern of Co / Cr when the substrate temperature was about 200 ° C. was almost the same as FIG. Further, this laminated film also had a Co (110) peak rocking curve half-width of about 3 °. Furthermore, when measured with a pole figure, a hexagonal C-axis deviation was observed in the magnetic field direction. Therefore, single crystal-like Co was obtained as compared with the laminated film formed at the substrate temperature of 100 ° C. and in the absence of a magnetic field.
[0315]
Next, FIG. 78 shows a RH curve in the hard axis direction of a laminated film having the same structure as that of FIG. 75 formed in a magnetic field at a substrate temperature of about 200.degree. The RH curve was created based on the value measured by the 4-terminal method after processing the laminated film into a 2 mm × 6 μm pattern in the same manner as described above. At this time, the easy axis (C-axis direction) was the pattern longitudinal direction, and the magnetic field was applied in the pattern width direction.
[0316]
As shown in FIG. 78, even when the external magnetic field is ± 1.6 kA / m, the magnetization of the high coercive force film hardly moves due to the applied magnetic field, and the saturation magnetic field of the NiFe film is also kept low at about 2.8 kA / m. I was able to. Also, the resistance change rate was about 7.5%.
[0317]
The laminated film having the above configuration has a stable magnetization even in an external magnetic field of 1.6 kA / m. Therefore, a pattern is formed in which the easy axis of the NiFe film is the width direction and the C axis of Co is approximately the longitudinal direction. did. This configuration eliminates the need for operating point bias. At this time, a magnetic field was applied in the pattern longitudinal direction, and the RH curve at that time was measured. The pattern shape was 2 mm × 6 μm as described above. The result is shown in FIG. As can be seen from FIG. 79, a good RH curve having no hysteresis was obtained, and Hk also showed a low value of about 1.6 kA / m.
[0318]
Further, although the Co film is used here as the high coercive force film, a CoNi film or a CoCr film may be used. Further, as the base film, a W film or the like may be used in addition to the Cr film, and an additive element may be added thereto based on these Cr and W. This undercoat film can be applied to a so-called hard film undercoat throughout the present invention. Thereby, the C axis can be present in the film surface of the hard magnetic film (the C axis is aligned in a specific direction). Therefore, when the hard magnetic film is fixed, it is possible to prevent the ferromagnetic film formed thereon from being fixed.
[0319]
Here, for reference, an MH curve of a laminated film without a base film is shown in FIG. It can be seen that a leakage magnetic field is generated from the perpendicular component of the magnetization of Co, degrading the soft magnetic properties of the NiFe film. This is considered that a part of magnetization of NiFe and Co is integrated.
[0320]
(Example 43)
As shown in Example 42, since the high coercivity film formed at a substrate temperature of about 200 ° C. is a single crystal-like film and has a low resistance, the mean free path of electrons is sufficiently longer than the thickness of the high coercivity film. it can. Therefore, as shown in FIG. 81, the high coercive force film 142 and the ferromagnetic film 144 are laminated via the Cu nonmagnetic film 143. The resistance change rate of this laminated film was as high as about 15%. In order to produce a laminated film having such a structure, it is desirable to provide a base film in order to control the orientation of the first high coercivity film 142. In this embodiment, a Cr film 141 having a thickness of 20 nm is used as the base film.
[0321]
(Example 44)
Next, the case where the high coercivity film for orientation control is used as a bias film in Example 34 will be described.
[0322]
In this example, as shown in FIG. 82, a magnetoresistive element having a spin valve structure was formed on a high coercivity film 142 for orientation control via a magnetic insulating layer 146. Thus, by using the orientation-controlled high coercivity film 142, the high coercivity film 142 and the NiFe film 144 are magnetostatically coupled at the film end, and the domain wall at the NiFe film end causing the Barkhausen noise is fixed. Can be made. In addition, since the orientation-controlled high coercive force film is used, the influence of the high coercive force film on the NiFe film, such as a leakage magnetic field inside the film, can be avoided, and a good element can be produced without deteriorating the soft magnetic properties of the NiFe film. it can. Here, an antiferromagnetic film or the like may be used as an exchange bias film having a spin valve structure.
[0323]
【The invention's effect】
As described above, the magnetoresistive effect element of the present invention can simultaneously exhibit a high rate of change in resistance and excellent soft magnetic characteristics, and has a great industrial value.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a magnetoresistive element (spin valve structure) according to a first invention of the present invention.
2 is a graph showing the external magnetic field dependence of the rate of change in resistance of the magnetoresistive effect element shown in FIG.
3A and 3B are graphs showing magnetization curves of the magnetoresistive effect element shown in FIG.
FIG. 4 is a cross-sectional view showing an example of a magnetoresistive element (artificial lattice film) according to the first invention of the present invention.
5 is a graph showing the external magnetic field dependence of the resistance change rate of the magnetoresistive effect element shown in FIG. 4;
FIG. 6 Co ₉₀ Fe _Ten The graph which shows the film thickness dependence of coercive force in case there exists Cu base film of a film | membrane.
FIG. 7 Co ₉₀ Fe _Ten The graph which shows the film thickness dependence of the coercive force in case there is no Cu base film of a film | membrane.
FIG. 8 is a cross-sectional view showing a magnetoresistive element (spin valve structure) according to the first aspect of the present invention.
9A is a θ-2θ scan X-ray diffraction curve on the sapphire substrate C surface, and FIG. 9B is a θ-2θ scan X-ray diffraction curve on the sapphire substrate R surface.
FIG. 10 Co ₉₀ Fe _Ten The rocking curve regarding the close-packed surface peak in the film / Cu film / sapphire substrate C surface.
FIG. 11 Co ₉₀ Fe _Ten The graph which shows the rocking curve half-width dependence in the close-packed surface reflection of the coercive force in a film | membrane.
FIG. 12 (Co ₉₀ Fe _Ten ) _1-x Al _x The graph which shows Al concentration x dependence of the coercive force in a film / Cu film.
FIG. 13: Co ₉₀ Fe _Ten The graph which shows the close-packed surface reflection intensity dependence of the coercive force in a film / Cu film.
FIG. 14 (Co ₉₀ Fe _Ten ) _1-x Ta _x The graph which shows Ta density x dependence of the coercive force in a film / Cu film.
FIG. 15 is a cross-sectional view showing a magnetoresistive element (spin valve structure) according to the first aspect of the present invention.
FIG. 16 is a cross-sectional view showing a magnetoresistive effect element according to a third invention of the present invention.
17 is an MH curve in the easy axis direction of the magnetoresistive effect element shown in FIG. 16;
18 is a MH curve in the hard axis direction of the magnetoresistive effect element shown in FIG.
19 is an RH curve of the magnetoresistive element shown in FIG.
FIG. 20 is a MH curve in the easy axis direction of a magnetoresistive effect element not provided with a high-resistance amorphous layer.
FIG. 21 is a MH curve in the hard axis direction of a magnetoresistive effect element not provided with a high-resistance amorphous layer.
FIG. 22 is a cross-sectional view showing a magnetoresistive effect element according to a third invention of the present invention.
23A to 23C are cross-sectional views showing the manufacturing process of another example of the magnetoresistive element of the third invention of the present invention.
FIG. 24 is a perspective view showing another example of the magnetoresistive effect element according to the third invention of the present invention.
FIG. 25 is a cross-sectional view showing an example of a magnetoresistive effect element according to a fourth invention of the present invention.
FIG. 26 shows Δρ / ρ in the magnetoresistive effect element shown in FIG. ₀ And d _CoFe The graph which shows the relationship.
FIG. 27 is a cross-sectional view showing a magnetoresistance effect element according to a fifth invention of the present invention.
FIG. 28 is a cross-sectional view showing a magnetoresistive effect element according to a fifth invention of the present invention.
FIG. 29 is a graph showing the dependence of coercive force on the thickness of a ferromagnetic film in a magnetoresistive effect element according to a sixth invention of the present invention.
FIG. 30 is a graph showing the dependence of the coercive force on the thickness of the ferromagnetic film in the magnetoresistive effect element according to the sixth aspect of the present invention.
FIG. 31 is a magnetization curve of a ferromagnetic film of a magnetoresistive effect element according to a sixth invention of the present invention.
FIG. 32 is a graph showing the stacking period dependency in the magnetoresistive effect element according to the seventh aspect of the present invention.
FIG. 33 is a graph showing the relationship between the saturation magnetic field Hs and the Cu film thickness in the ferromagnetic film of the magnetoresistive effect element according to the sixth aspect of the present invention.
FIG. 34 is a magnetization curve of a ferromagnetic film of a magnetoresistive effect element according to a seventh aspect of the present invention.
FIG. 35 is a cross-sectional view showing a magnetoresistive effect element according to a seventh invention of the present invention.
FIG. 36 is a sectional view showing an interface state between Cu and CoFe in the seventh invention.
37 is a magnetization curve of the magnetoresistance effect element shown in FIG. 35. FIG.
38 is a graph showing resistance change characteristics of the magnetoresistive effect element shown in FIG. 35;
FIG. 39 is a magnetization curve of a conventional magnetoresistive effect element.
FIG. 40 is a graph showing resistance change characteristics of a conventional magnetoresistive element.
41A and 41B are magnetization curves of a ferromagnetic film having a Cu underlayer of the magnetoresistive effect element according to the seventh aspect of the present invention.
FIG. 42 is a graph showing resistance change characteristics of a ferromagnetic film having a Cu underlayer of the magnetoresistance effect element according to the seventh aspect of the present invention.
FIG. 43 is a cross-sectional view showing a magnetoresistive effect element according to a fourth invention of the present invention.
44 is a magnetization curve of the magnetoresistance effect element shown in FIG. 43. FIG.
45 is a graph showing resistance change characteristics of the magnetoresistive effect element shown in FIG. 43;
FIG. 46 is a schematic diagram for explaining fluctuations in the film.
FIG. 47A shows Co on MgO (110) plane substrate. ₉₀ Fe _Ten X-ray diffraction curve of small angle reflection of Cu / Cu artificial lattice film, (B) is Co on MgO (110) plane substrate ₉₀ Fe _Ten X-ray diffraction curve of medium angle reflection of Cu / Cu artificial lattice film.
48A is a rocking curve measured from the [110] axis direction related to the fcc (220) reflection in FIG. 47, and FIG. 48B is a rocking curve measured from the [100] axis direction related to the fcc (220) reflection in FIG. curve.
49A is a schematic diagram showing the in-plane distribution of the normal of the crystal orientation plane due to fluctuations in the crystal orientation plane, and FIG. 49B is a schematic diagram showing the dependence of the resistance change rate on the sense current direction.
FIG. 50A shows Cu 5.5 nm / (Cu 1.1 nm / CoFe 1 nm). ₁₆ Magnetization curve in the external magnetic field [100] axis direction of the artificial lattice film, (B) is Cu 5.5 nm / (Cu 1.1 nm / CoFe 1 nm) ₁₆ Magnetization curve in the external magnetic field [110] axial direction of the artificial lattice film.
FIG. 51: Co on MgO (110) plane substrate ₉₀ Fe _Ten The graph which shows the bias voltage dependence of the resistance change rate of / Cu laminated film.
FIG. 52 shows Co with fcc phase (111) orientation. ₉₀ Fe _Ten FIG. 6 is a conceptual diagram when a stacking fault is introduced into a Cu stacked film.
FIG. 53 shows Co with fcc phase (111) orientation. ₉₀ Fe _Ten The conceptual diagram which shows an atomic arrangement | sequence when a stacking fault is introduce | transduced into / Cu laminated film.
FIG. 54 shows Co in the fcc phase (111) plane orientation. ₉₀ Fe _Ten The conceptual diagram which shows an atomic arrangement | sequence when a twin defect is introduce | transduced into / Cu laminated film.
55 is a schematic diagram showing the dependence of the resistance change rate on the sense current direction in the state shown in FIG. 54. FIG.
FIG. 56: Co on glass substrate ₉₀ Fe _Ten The graph which shows the substrate bias dependence of the resistance change rate of / Cu artificial lattice film.
FIG. 57: Co on glass substrate ₉₀ Fe _Ten The graph which shows the bias dependence of the long period structure reflection intensity of / Cu artificial lattice film.
FIG. 58: Co on glass substrate ₉₀ Fe _Ten The graph which shows the bias dependence of the fcc phase (111) surface reflection intensity of / Cu artificial lattice film.
FIG. 59: Co on glass substrate ₉₀ Fe _Ten The graph which shows the bias dependence of the coercive force of / Cu artificial lattice film.
FIG. 60 is a perspective view showing a magnetoresistive effect element according to an eighth aspect of the present invention.
FIG. 61 is a perspective view showing a magnetoresistive effect element according to an eighth aspect of the present invention.
FIG. 62 is a perspective view showing a magnetoresistive effect element according to an eighth aspect of the present invention.
FIG. 63 is a perspective view showing a magnetoresistive effect element according to an eighth aspect of the present invention.
FIG. 64 is a perspective view showing a magnetoresistive effect element according to an eighth aspect of the present invention.
FIG. 65 is a perspective view showing a magnetoresistive effect element according to an eighth aspect of the present invention.
FIG. 66 is a graph showing resistance change characteristics of the magnetoresistance effect element according to the eighth aspect of the present invention;
FIG. 67 is a perspective view showing a magnetoresistance effect element according to a twelfth aspect of the present invention.
FIG. 68 is a perspective view showing a magnetoresistive effect element according to a twelfth aspect of the present invention.
FIG. 69 is a perspective view showing a magnetoresistance effect element according to a tenth aspect of the present invention.
70A to 70C are perspective views showing a magnetoresistive effect element according to a tenth aspect of the present invention.
FIG. 71 is a perspective view showing a magnetoresistance effect element according to a tenth aspect of the present invention.
FIG. 72 is a graph showing resistance change characteristics of the laminated film of the magnetoresistance effect element according to the tenth aspect of the present invention;
FIG. 73 is a perspective view showing a magnetoresistance effect element according to a twelfth aspect of the present invention.
FIG. 74 is a cross-sectional view showing a magnetoresistive effect element according to a twelfth aspect of the present invention.
FIG. 75 is a cross-sectional view showing a magnetoresistance effect element according to a thirteenth aspect of the present invention.
FIG. 76 shows an X-ray diffraction pattern of a Co / Cr laminated film.
77 is an RH curve of a laminated film of the thirteenth aspect of the present invention formed at a substrate temperature of about 100 ° C. FIG.
78 is an RH curve of a laminated film of the thirteenth aspect of the present invention formed at a substrate temperature of about 200 ° C. FIG.
FIG. 79 is an RH curve of the laminated film of the thirteenth aspect of the present invention when the pattern width direction is the easy axis.
FIG. 80 is an RH curve of the laminated film of the thirteenth aspect of the present invention when no base film is provided.
FIG. 81 is a cross-sectional view showing a magnetoresistive effect element according to a thirteenth aspect of the present invention.
FIG. 82 is a cross-sectional view showing a magnetoresistive effect element according to a thirteenth aspect of the present invention.
FIG. 83 is a perspective view showing a conventional magnetoresistive element.
FIG. 84 is a RH curve of a conventional magnetoresistive element.
[Explanation of symbols]
10, 20 ... sapphire substrate, 11, 21, 71 ... Co ₉₀ Fe _Ten Film, 12, 22, 23, 70 ... Cu film, 13 ... FeMn film, 14 ... Ti film, 15, 24 ... Cu lead, 26 ... Ni oxide film, 30, 41, 140 ... Support substrate, 31, 46 ... High resistance amorphous layer, 32, 44, 83, 85, 91, 93, 103, 105, 107, 112, 114, 116, 118, 121, 123, 132, 134, 136, 144... Ferromagnetic film, 33, 45 , 143 ... intermediate layer, 34 ... exchange bias layer, 35, 47 ... lead, 42 ... CoPtCr film, 43 ... resist, 50, 80, 90, 100, 120, 130 ... substrate, 51 ... ferromagnetic laminated unit, 52, 84, 87, 88, 92, 104, 106, 113, 115, 117, 122, 133, 135, 163 ... nonmagnetic film, 53, 82, 94, 102, 108, 111, 119, 24, 131, 137, 165 ... antiferromagnetic film, 54, 166 ... protective film, 55, 62, 86, 96, 109, 125, 145 ... electrode terminal, 60 ... MgO substrate, 61 ... laminated film, 81, 101 141 ... Underlayer film, 95 ... Hard magnetic film, 97 ... Insulating film, 142 ... High coercive force film, 146 ... Magnetic insulating layer, 160 ... Thermally oxidized Si substrate, 161 ... High-resistance ferromagnetic film, 162 ... First Ferromagnetic film, 164, second ferromagnetic film, 167a, 167b, electrode, 169, high resistance antiferromagnetic film.

Claims (18)

First and second ferromagnetic films separated by a first nonmagnetic metal film;
A first antiferromagnetic film configured to fix the magnetization direction of the first ferromagnetic film and including PtMn;
A sense current is connected to the first and second ferromagnetic films and the first nonmagnetic metal film, and supplies a sense current for detecting a resistance change accompanying a magnetization rotation of the second ferromagnetic film due to a signal magnetic field. A magnetoresistive effect element comprising: a pair of lead electrodes configured as described above. A first ferromagnetic film;
A second ferromagnetic film disposed adjacent to the first ferromagnetic film and sandwiching the first nonmagnetic metal film therebetween;
A first antiferromagnetic film disposed in contact with the first ferromagnetic film, configured to fix the magnetization direction of the first ferromagnetic film, and including PtMn;
A magnetoresistive effect element characterized in that the magnetization direction of the first ferromagnetic film is substantially perpendicular to the magnetization direction of the second ferromagnetic film when the applied magnetic field is zero. A first ferromagnetic film;
A second ferromagnetic film disposed adjacent to the first ferromagnetic film and sandwiching the first nonmagnetic metal film therebetween;
A first antiferromagnetic film disposed in contact with the first ferromagnetic film and containing PtMn;
A magnetoresistive effect characterized in that one close-packed surface of each of the first and second ferromagnetic films is oriented in a direction perpendicular to one of the first and second ferromagnetic films. element. The magnetoresistive effect element according to any one of claims 1 to 3, wherein the first antiferromagnetic film has a thickness of 5 to 50 nm. The second ferromagnetic film, the first nonmagnetic metal film, the first ferromagnetic film, and the first antiferromagnetic film are laminated in order from the bottom. The magnetoresistive effect element of any one of Claims. The first antiferromagnetic film, the first ferromagnetic film, the first nonmagnetic metal film, and the second ferromagnetic film are laminated in order from the bottom. The magnetoresistive effect element of any one of Claims. The magnetoresistive effect element according to claim 1, wherein the first ferromagnetic film includes an alloy selected from the group consisting of Co or CoFe and NiFe. 8. The magnetoresistive element according to claim 1, wherein the first ferromagnetic film contains Co or CoFe, and the second ferromagnetic film contains NiFe. 9. A second nonmagnetic metal film, a third ferromagnetic film, and a second antiferromagnetic film made of PtMn, wherein the second and third ferromagnetic films are separated by the second nonmagnetic metal film. 9. The magnetoresistive element according to claim 1, wherein the second antiferromagnetic film is laminated on the third ferromagnetic film. 10. The magnetoresistive element according to claim 1, wherein the first antiferromagnetic film is formed over the entire surface of the first ferromagnetic film. 11. 11. The magnetoresistive element according to claim 1, wherein the first ferromagnetic film and the first antiferromagnetic film are exchange coupled. 12. The magnetoresistive element according to claim 1, wherein a magnetic permeability of the second ferromagnetic film is higher than a magnetic permeability of the first ferromagnetic film. The one of the first and second ferromagnetic films includes a material selected from the group consisting of Co, CoFe, CoNi, NiFe, and NiFeCo. Magnetoresistive effect element. The one of the first and second ferromagnetic films has a close-packed surface oriented in a direction perpendicular to one film surface of the first and second ferromagnetic films. 14. The magnetoresistive effect element according to any one of 2 or 4 to 13. 15. The magnetoresistive effect element according to claim 1, wherein the close-packed surface is an fcc phase (111) surface. 15. The magnetoresistive effect element according to claim 1, wherein the close-packed surface is an hcp phase (001) surface. 17. The magnetization of the first ferromagnetic film does not substantially rotate in a signal magnetic field weaker than a signal magnetic field in which the magnetization of the second ferromagnetic film rotates. The magnetoresistive effect element according to item. A magnetic reproducing system comprising a magnetic head provided with the magnetoresistive effect element according to claim 1.

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