JP3936137B2 - Magneto-impedance effect element - Google Patents

Description

（数１）から、前記感磁部の素子幅Ｗ、素子長さＬ、比抵抗ρ、励磁周波数ωを一定としたとき、前記感磁部のインピーダンスの大きさ｜Ｚ｜は、素子幅方向の透磁率μの１／２乗に比例することがわかる。素子長手方向に交流電流が与えられ、素子幅方向に励磁されている前記感磁部の素子長手方向に、外部磁界が印加されると、前記感磁部の素子幅方向の透磁率μが変化し、前記感磁部のインピーダンスの大きさ｜Ｚ｜が変化する。この、前記感磁部のインピーダンスの大きさ｜Ｚ｜の変化を測定することにより、前記感磁部に印加された前記外部磁界を検知する。
【００３０】
アスペクト比Ｗ／Ｌが小さくなると、素子幅方向の透磁率μの変化に対するインピーダンスの大きさ｜Ｚ｜の変化率が大きくなる。すなわち、前記感磁部の両端から引き出される出力電圧の大きさの変化が大きくなり、磁気インピーダンス効果素子の磁界検出感度が向上する。
【００３１】
また、前記感磁部の素子幅Ｗと素子長さＬの比（アスペクト比）Ｗ／Ｌが、０．０５以下であることが好ましく、より好ましくは、前記感磁部の素子幅Ｗと素子長さＬの比（アスペクト比）Ｗ／Ｌが、０．０３以下であることである。
【００３２】
なお、前記感磁部がＵ字型、つづら折れ状に形成される場合には、前記感磁部の素子長手方向を向いた部位の長さの総和が素子長さＬとなる。このときの素子長手方向とは、前記感磁部の中のもっとも長い直線部分の延長方向であり、駆動交流電流によって発生する磁界の励磁方向に対して垂直な方向に一致する。
【００３４】
前記軟磁性体部が、単磁区構造或いは多磁区構造を有し、各磁区において磁気モーメントの素子長手方向の成分と素子幅方向の成分を比較したときに、前記素子長手方向の成分の方が大きい磁区の総面積と、前記素子幅方向の成分の方が大きい磁区の総面積が等しくなっていると、前記軟磁性体部の、全体としての磁気異方性の方向がほぼ等方的な状態になる。
【００３５】
つまり、前記軟磁性体部の磁気モーメントがある方向に固定されにくくなり、前記軟磁性体部を有する前記感磁部が交流電流によって励磁されたときに、軟磁性体部の磁気モーメントの方向を変化させやすくなる。すなわち、軟磁性体部の素子幅方向の透磁率μが増加し、前記外部磁界を印加しないときに、軟磁性体部の素子幅方向の透磁率μが最大値をとる。軟磁性体部の素子幅方向の透磁率μが最大値をとるとき、軟磁性体部のインピーダンスの大きさＺが最大となり、前記感磁部の両端からの出力電圧も最大になる。すなわち、前記感磁部の両端からの出力電圧を最大にさせる外部磁界の大きさの絶対値が０に近くなる。
【００３７】
前記軟磁性体部の各磁区において、磁気モーメントの素子長手方向の成分と素子幅方向の成分を比較したときに、前記素子長手方向の成分の方が大きい磁区の総面積が、前記素子幅方向の成分の方が大きい磁区の総面積より大きい場合においても、前記感磁部を構成する軟磁性体部の磁気異方性の方向を全体として等方的な状態に近い状態にすることができ、前記素子幅方向の成分の方が大きい磁区の総面積と、前記素子長手方向の成分の方が大きい磁区の総面積とが等しい磁区構造の感磁部を有する磁気インピーダンス効果素子と同等の磁界検出感度を得ることができる。
【００３８】
また、前記感磁部を構成する軟磁性体部の磁気異方性の方向が全体として等方的な状態に近い状態であると、前記感磁部の素子長手方向にわずかに外部磁界を印加するだけで、前記軟磁性体部の磁気異方性の方向を全体としてほぼ等方的な状態にさせることができ、前記感磁部の素子幅方向の透磁率μを最大にさせることができ、さらに前記感磁部の両端からの出力電圧を最大にさせることができる。すなわち、前記感磁部の両端からの出力電圧を最大にさせる外部磁界の大きさの絶対値を小さくさせることができる。
【００３９】
また、本発明の磁気インピーダンス効果素子が、前記感磁部の素子長手方向と平行な方向にバイアス磁界を印加する磁性体を有するものであると、製造工程を簡略化でき、小型化が容易で、かつ消費電力を少なくすることができるので好ましい。
【００４０】
前記磁気インピーダンス効果素子の感磁部は、軟磁気特性を備えた強磁性体を有することが必要である。また、１ＭＨｚ〜数百ＭＨｚの高周波領域において透磁率μが高くなくてはならない。さらに、外部磁界（放送電波の磁界成分）によって軟磁性体に応力がかかって磁気特性が劣化しないように、磁歪定数λが小さいことが好ましい。
【００４１】
前記軟磁性体が、このような性質を備えた薄膜磁性体として形成されるために、前記軟磁性体が以下に示すような微結晶軟磁性合金薄膜として形成されることが好ましい。
【００４２】
１．組成式が、Ｆｅ_hＭ_iＯ_jで表され、アモルファス構造を主体とした微結晶軟磁性合金薄膜。
【００４３】
ただし、Ｍは、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｗと希土類元素から選ばれる１種あるいは２種以上の元素であり、ｈ、ｉ、ｊはａｔ％で、４５≦ｈ≦７０、５≦ｉ≦３０、１０≦ｊ≦４０、ｈ＋ｉ＋ｊ＝１００の関係を満足するもの。
【００４４】
Ｆｅは大きい飽和磁束密度Ｂｓを得るためのものであり、ＭはＯと化合し、比抵抗ρを大きくするためのものである。ｈ、ｉ、ｊが上記範囲であると、飽和磁束密度Ｂｓ、比抵抗ρ、透磁率μが大きい軟磁性合金を得ることができ、ｈ、ｉ、ｊが上記範囲を外れると、軟磁気特性が劣化する。
【００４５】
なお、上記組成において元素Ｍが希土類元素から選ばれる１種あるいは２種以上の元素である場合には、ｈ、ｊはａｔ％で５０≦ｈ≦７０、１０≦ｊ≦３０であることがより好ましい。
【００４６】
２．組成式が、（Ｃｏ_1-cＴ_c）_xＭ_yＸ_zＯ_wで表される微結晶軟磁性合金薄膜。
ただし、元素Ｔは、Ｆｅ、Ｎｉのうちどちらか一方あるいは両方を含む元素であり、元素Ｍは、Ｔｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｃｒ，Ｍｏ，Ｓｉ，Ｐ，Ｃ，Ｗ，Ｂ，Ａｌ，Ｇａ，Ｇｅと希土類元素から選ばれる１種または２種以上の元素であり、Ｘは、Ａｕ，Ａｇ，Ｃｕ，Ｒｕ，Ｒｈ，Ｏｓ，Ｉｒ，Ｐｔ，Ｐｄから選ばれる１種あるいは２種以上の元素であり、組成比は、ｃが、０≦ｃ≦０．７、ｘ，ｙ，ｚ，ｗはａｔ％で、３≦ｙ≦３０、０≦ｚ≦２０、７≦ｗ≦４０、２０≦ｙ＋ｚ＋ｗ≦６０の関係を満足し、残部がｘであるもの。
【００４７】
なお、軟磁性合金は、元素Ｍの酸化物を多量に含むアモルファス相に、Ｃｏと元素Ｔを主体とする微結晶相が混在し、さらに微結晶相は、元素Ｍの酸化物を含んだ構造を有するものであるとより好ましい。
【００４８】
３．組成式が、Ｔ_100-d-e-f-gＸ_dＭ_eＺ_fＱ_gで表され、ｂｃｃ−Ｆｅ、ｂｃｃ−ＦｅＣｏ、ｂｃｃ−Ｃｏの１種または２種以上の結晶粒を主体とした微結晶軟磁性合金薄膜。
【００４９】
ただし、元素Ｔは、Ｆｅ、Ｃｏのうちどちらか一方あるいは両方を含む元素であり、元素Ｘは、Ｓｉ、Ａｌのうちどちらか一方あるいは両方を含む元素であり、元素Ｍは、Ｔｉ、Ｚｒ、Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｍｏ，Ｗから選ばれる１種または２種以上の元素であり、元素Ｚは、Ｃ、Ｎのうちどちらか一方あるいは両方を含む元素であり、Ｑは、Ｃｒ，Ｒｅ，Ｒｕ，Ｒｈ，Ｎｉ，Ｐｄ，Ｐｔ，Ａｕから選ばれる１種または２種以上の元素であり、ｄ、ｅ、ｆ、ｇはａｔ％で、０≦ｄ≦２５、１≦ｅ≦１０、０．５≦ｆ≦１５、０≦ｇ≦１０の関係を満足するもの。
【００５０】
ｄ、ｅ、ｆ、ｇが上記範囲内にあれば、透磁率μが大きく、保磁力Ｈｃも低く、磁歪定数λも小さい軟磁性合金薄膜を得ることができる。
【００５１】
４．組成式が、Ｔ_{100-p-q-e-f-g}Ｓｉ_pＡｌ_qＭ_eＺ_fＱ_gで表され、ｂｃｃ−Ｆｅ、ｂｃｃ−ＦｅＣｏ、ｂｃｃ−Ｃｏの１種または２種以上の結晶粒を主体とした微結晶軟磁性合金薄膜。
【００５２】
ただし、元素Ｔは、Ｆｅ、Ｃｏのうちどちらか一方あるいは両方を含む元素であり、元素Ｍは、Ｔｉ、Ｚｒ、Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｍｏ，Ｗから選ばれる１種または２種以上の元素であり、元素Ｚは、Ｃ、Ｎのうちどちらか一方あるいは両方を含む元素であり、Ｑは、Ｃｒ，Ｒｅ，Ｒｕ，Ｒｈ，Ｎｉ，Ｐｄ，Ｐｔ，Ａｕから選ばれる１種または２種以上の元素であり、ｐ、ｑ、ｅ、ｆ、ｇはａｔ％で、８≦ｐ≦１５、０≦ｑ≦１０、１≦ｅ≦１０、０．５≦ｆ≦１５、０≦ｇ≦１０の関係を満足するもの。
【００５３】
ｐ、ｑ、ｅ、ｆ、ｇが上記範囲内にあれば、透磁率μが大きく、保磁力Ｈｃも低く、磁歪定数λも小さい軟磁性合金を得ることができる。
【００５４】
また、前記感磁部が、以下に示すような非晶質軟磁性合金薄膜または薄帯を有するものとして形成されていてもよい。
【００５５】
５．組成式が、（Ｆｅ_1-aＣｏ_a）_100-x-y（Ｓｉ_1-bＢ_b）_xＭ_yで示される非晶質軟磁性合金薄膜または薄帯。
【００５６】
ただし、ＭはＣｒ、Ｒｕのうちいずれか一方、あるいは両方を含む元素であり、組成比を表すａ、ｂは０．０５≦ａ≦０．１、０．２≦ｂ≦０．８であり、ｘ、ｙはａｔ％で１０≦ｘ≦３５、０≦ｙ≦７の関係を満足するもの。
【００５７】
前記（Ｆｅ_1-aＣｏ_a）_100-x-y（Ｓｉ_1-bＢ_b）_xＭ_y系の軟磁性合金薄膜又は薄帯では、ａが０．０５≦ａ≦０．１の範囲を越えると、磁歪が大きくなるので好ましくない。また、ｂが０．２≦ｂ≦０．８の範囲を越えると、非晶質化が困難になり好ましくない。さらに、ｘが１０≦ｘ≦３５の範囲を越えると非晶質化が困難になり好ましくない。また、ｘ＞３５であると磁気特性が劣化するので好ましくない。
【００５８】
６．組成式が、Ｃｏ_lＴａ_mＨｆ_nで表され、アモルファス構造を主体にした非晶質軟磁性合金薄膜。
【００５９】
ただし、ｌ、ｍ、ｎはａｔ％で、７０≦ｌ≦９０、５≦ｍ≦２１、６．６≦ｎ≦１５、１≦ｍ／ｎ≦２．５の関係を満足するもの。
【００６０】
前記Ｃｏ_lＴａ_mＨｆ_n系の軟磁性合金薄膜においては、飽和磁束密度ＢｓはＣｏの含有量に依存しており、高い飽和磁束密度Ｂｓを得るには、７０≦ｌであることが必要である。しかし、ｌ＞９０であると、比抵抗ρが低くなるので好ましくない。
【００６１】
ＴａおよびＨｆは軟磁気特性を得るための元素であり、５≦ｍ≦２１、６．６≦ｎ≦１５とすることにより、飽和磁束密度Ｂｓが大きく、比抵抗ρも大きい軟磁性材料を得ることができる。また、Ｈｆは、Ｃｏ−Ｔａ系において発生する負の磁歪定数λを解消するための元素でもある。磁歪定数λは、Ｔａの含有量とＨｆの含有量の比に依存し、１≦ｍ／ｎ≦２．５の範囲内であると、磁歪定数λを良好に解消することができる。
【００６２】
７．組成式が、Ｃｏ_aＺｒ_bＮｂ_cで表されるアモルファス構造を主体とした非晶質軟磁性合金薄膜。
【００６３】
ただし、ａ、ｂ、ｃはａｔ％で、７８≦ａ≦９１、０．５≦ｂ／ｃ≦０．８の関係を満足するもの。
【００６４】
飽和磁束密度ＢｓはＣｏの濃度に依存し、Ｂｓを大きくするためには、７８≦ａ≦９１にする必要がある。ａ＞９１であると、耐食性が低下すると共にアモルファス構造になりにくくなり、結晶化し始めるので好ましくない。また、ａ＜７８であると、Ｃｏどうしが隣接する割合が減り、軟磁気特性を示しにくくなるので好ましくない。透磁率μも、Ｃｏの濃度に依存し、７８≦ａ≦９１の範囲で高い値を示す。
【００９１】
【発明の実施の形態】
図１は、本発明の第１の実施の形態の磁気インピーダンス効果素子を示す斜視図である。
【００９２】
図１の磁気インピーダンス効果素子Ｍは、アルミナチタンカーバイドなどの非磁性材料からなる基板２１上に、軟磁性体部である軟磁性薄膜２２、導電体部である導電性薄膜２３、及び軟磁性薄膜２４が順次積層されて形成された感磁部２５、および感磁部２５の両端部にＣｕ、Ｎｉ、Ｔｉ、Ｃｒなどの導電性材料により形成された電極部２６，２６によって構成されている。感磁部２５は、略長方形状または線状にパターン形成されている。また、感磁部２５はＵ字形状またはジグザグ状に形成されてもよい。
【００９３】
なお、図１では、電極部２６，２６が感磁部２５の素子長手方向の両端部に形成されているが、電極部２６，２６は、軟磁性薄膜２４の上面の両端部付近上にＣｕなどの導電性材料を積層して形成されてもよい。
【００９４】
磁気インピーダンス効果素子Ｍに電極部２６，２６から素子長手方向（Ｙ方向）に駆動交流電流を与え、感磁部２５を素子幅方向（Ｘ方向）に励磁する。この状態で、外部磁界Ｈｅｘが素子長手方向に印加されると、感磁部２５のインピーダンスが変化する。感磁部２５のインピーダンス変化を、電極部２６，２６間の電圧の変化として取り出す。
【００９５】
ここで、素子長手方向は、駆動交流電流によって発生する磁界の励磁方向に対して垂直な方向に一致する。
【００９６】
また、感磁部２５がＵ字型やつづら折れ形状で形成されているときは、感磁部の中のもっとも長い直線部分の延長方向が素子長手方向となり、この方向が駆動交流電流によって発生する磁界の励磁方向に対して垂直な方向に一致する。
【００９７】
なお、感磁部２５上に、絶縁材料からなる保護層が形成されてもよい。
軟磁性薄膜２２，２４は、例えば、組成式がＦｅ_71.4Ａｌ_5.8Ｓｉ_13.1Ｈｆ_3.3Ｃ_4.5Ｒｕ_1.9（ａｔ％）で表される、ｂｃｃ−Ｆｅの結晶粒を主体とし、ｂｃｃ−Ｆｅの周囲にＨｆＣの結晶粒が存在する平均結晶粒径５〜３０ｎｍの微結晶軟磁性合金薄膜である。
【００９８】
この組成以外のＴ―Ｘ―Ｍ―Ｚ―Ｑ系（元素Ｔは、Ｆｅ、Ｃｏのうちどちらか一方あるいは両方を含む元素であり、元素Ｘは、Ｓｉ、Ａｌの内どちらか一方あるいは両方を含む元素であり、元素Ｍは、Ｔｉ、Ｚｒ、Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｍｏ，Ｗから選ばれる１種または２種以上の元素であり、元素Ｚは、Ｃ、Ｎのうちどちらか一方あるいは両方を含む元素であり、Ｑは、Ｃｒ，Ｒｅ，Ｒｕ，Ｒｈ，Ｎｉ，Ｐｄ，Ｐｔ，Ａｕから選ばれる１種または２種以上の元素）の微結晶軟磁性合金薄膜や、Ｃｏ−Ｔ−Ｍ−Ｘ―Ｏ系（元素Ｔは、Ｆｅ、Ｎｉのうちどちらか一方あるいは両方を含む元素であり、元素Ｍは、Ｔｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｃｒ，Ｍｏ，Ｓｉ，Ｐ，Ｃ，Ｗ，Ｂ，Ａｌ，Ｇａ，Ｇｅと希土類元素から選ばれる１種または２種以上の元素であり、Ｘは、Ａｕ，Ａｇ，Ｃｕ，Ｒｕ，Ｒｈ，Ｏｓ，Ｉｒ，Ｐｔ，Ｐｄから選ばれる１種あるいは２種以上の元素）の組成を有し、ｂｃｃ−Ｆｅ、ｂｃｃ−ＦｅＣｏ、ｂｃｃ−Ｃｏ等からなる平均結晶粒径１０〜３０ｎｍの結晶相とＭの酸化物を含む非晶質相からなり、非晶質相が組織全体の５０％以上を占めている微結晶軟磁性合金薄膜や、Ｆｅ―Ｍ―Ｏ系（Ｍは、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｗと希土類元素から選ばれる１種あるいは２種以上の元素）の組成を有し、ｂｃｃ−Ｆｅを主体とする平均結晶粒径１０〜３０ｎｍの結晶相とＭの酸化物を含む非晶質相からなり、非晶質相が組織全体の５０％以上を占めている微結晶軟磁性合金薄膜として、軟磁性薄膜２２，２４が形成されていてもよい。
【００９９】
あるいは、Ｆｅ−Ｃｏ−Ｓｉ−Ｂ―Ｍ系（Ｍは、Ｃｒ，Ｒｕのうちいずれか一方あるいは両方を含む元素）の非晶質軟磁性合金薄膜や、Ｃｏ―Ｔａ―Ｈｆ系の非晶質軟磁性合金薄膜や、Ｃｏ−Ｚｒ−Ｎｂ系の非晶質軟磁性合金薄膜として、軟磁性薄膜２２，２４が形成されていてもよい。
【０１００】
導電性薄膜２３は、Ｃｕ、Ｎｉ、Ｔｉ、Ｃｒなどの導電性材料により形成される。また、導電性薄膜２３を形成するために用いる材料は、軟磁性薄膜２２，２４より比抵抗の低い材料であれば、どのようなものでもかまわない。例えば、Ｆｅ，Ｃｏを含む強磁性材料であっても、ＮｉＯ，ＣｏＯなどの反強磁性材料であってもよい。ただし、導電性薄膜２３を形成するために用いる材料の比抵抗は、軟磁性薄膜２２，２４を形成するために用いる材料の比抵抗の１／１０以下の比抵抗の材料であることが好ましい。
【０１０１】
本実施の形態では、感磁部２５が軟磁性薄膜２２，２４と導電性薄膜２３とが交互に積層されたものとして形成されている。軟磁性材料からなる軟磁性薄膜２２，２４と、この軟磁性材料よりも比抵抗の低い材料によって形成された導電性薄膜２３とが接した構造を有していると、感磁部２５に駆動交流電流が与えられたときに、この駆動交流電流は軟磁性薄膜２２，２４内を流れる電流と導電性薄膜２３内を流れる電流とに分れて流れる。その結果、前記駆動交流電流が流れるときの感磁部２５の直流抵抗値が低くなり、磁気インピーダンス効果素子の消費電力を小さくすることができる。
【０１０２】
また、感磁部２５が、透磁率の高い軟磁性薄膜２２，２４と導電率の高い導電性薄膜２３とが接した構造を有しているために、前記感磁部内を流れる駆動交流電流の表皮厚さが薄くなり、大きな磁気インピーダンス効果を発生させることができる。従って、低駆動電圧であっても磁界に対する充分な出力電圧の変化量を得ることができる。
【０１０３】
図２は、本発明の第２の実施の形態の磁気インピーダンス効果素子の感磁部の断面図である。
【０１０４】
図２の磁気インピーダンス効果素子は、アルミナチタンカーバイドなどの非磁性材料からなる基板２１上に、軟磁性体部である軟磁性薄膜３２、導電体部である導電性薄膜３３、及び軟磁性薄膜３４が順次積層されて形成された感磁部３５を有している。本実施の形態では、感磁部３５の、最上層の軟磁性薄膜３４と最下層の軟磁性薄膜３２とが、素子幅方向の端部において磁気的に結合されており、感磁部３５に駆動交流電流が流されたときに、軟磁性薄膜３４と軟磁性薄膜３２に閉じた周回磁界が発生させることができる。
【０１０５】
図３は、本発明の第３の実施の形態の磁気インピーダンス効果素子の感磁部の断面図である。
【０１０６】
図３の磁気インピーダンス効果素子は、アルミナチタンカーバイドなどの非磁性材料からなる基板２１上に、軟磁性体部である軟磁性薄膜４２、導電体部である導電性薄膜４３、及び軟磁性薄膜４４が順次積層されて形成された感磁部４５を有している。本実施の形態では、感磁部４５が基板２１の表面２１ａから離れるにつれて、素子幅方向（Ｙ方向）寸法が徐々に短くなるものとして形成されている。従って、膜応力を分散できて、感磁部４５が基板から剥がれることを防止でき、また、感磁部４５を安定した形状に維持できる。
【０１０７】
なお、感磁部４５の断面形状は、図３のような形状に限らず、感磁部４５の上面４５ａの素子幅方向寸法が、感磁部４５の底面４５ｂの素子幅方向寸法より短くされていればよい。例えば、感磁部４５の素子幅方向の両端部が階段状に形成されても良い。
【０１０８】
図４は、本発明の第４の実施の形態の磁気インピーダンス効果素子の感磁部の断面図である。
【０１０９】
本発明の磁気インピーダンス効果素子は、必ずしも、軟磁性薄膜と導電性薄膜が、上下方向に順次積層されたものでなくともよい。
【０１１０】
例えば、図４に示されるように、アルミナチタンカーバイドなどの非磁性材料からなる基板２１の表面２１ａの同一面上に、軟磁性薄膜５２、導電性薄膜５３、及び軟磁性薄膜５４が形成され、軟磁性薄膜５２及び導電性薄膜５３が互いに接触し、さらに、導電性薄膜５３及び軟磁性薄膜５４が互いに接触した構造を有する感磁部５５を有する磁気インピーダンス効果素子であってもよい。
【０１１１】
図４の感磁部５５を有する磁気インピーダンス効果素子でも、感磁部５５に駆動交流電流が与えられたときに、この駆動交流電流は軟磁性薄膜５２，５４内を流れる電流と導電性薄膜５３内を流れる電流とに分れて流れる。その結果、前記駆動交流電流が流れるときの感磁部５５の直流抵抗値が低くなり、磁気インピーダンス効果素子の消費電力を小さくすることができる。
【０１１２】
また、感磁部５５が、透磁率の高い軟磁性薄膜５２，５４と導電率の高い導電性薄膜５３とが接した構造を有しているために、前記感磁部内を流れる駆動交流電流の表皮厚さが薄くなり、大きな磁気インピーダンス効果を発生させることができる。従って、低駆動電圧であっても磁界に対する充分な出力電圧の変化量を得ることができる。
【０１１３】
図５は、本発明の第５の実施の形態の磁気インピーダンス効果素子の感磁部の断面図である。
【０１１４】
本発明では、感磁部の軟磁性薄膜と導電性薄膜が何層積層されてもかまわない。
【０１１５】
例えば、図５のように、アルミナチタンカーバイドなどの非磁性材料からなる基板２１上に、軟磁性体部である軟磁性薄膜６２、導電体部である導電性薄膜６３、軟磁性薄膜６４、導電性薄膜６５、軟磁性薄膜６６が順次積層されて形成された感磁部６７を有した磁気インピーダンス効果素子でもよい。
【０１１６】
なお、最上層の軟磁性薄膜６６と最下層の軟磁性薄膜６２とが、素子幅方向の端部において磁気的に結合されていてもよい。また、感磁部６７が基板２１の表面２１ａから離れるにつれて、素子幅方向（Ｙ方向）寸法が徐々に短くなるものとして形成されてもよい。
【０１１７】
図６は、本発明の第６の実施の形態の磁気インピーダンス効果素子の感磁部の断面図である。
【０１１８】
本発明では、必ずしも、感磁部の導電性薄膜が，複数の軟磁性薄膜によって挟まれていなくともよい。
【０１１９】
例えば、図６のように、アルミナチタンカーバイドなどの非磁性材料からなる基板２１上に、軟磁性薄膜７２及び導電性薄膜７３のみが順次積層されて形成された感磁部７４を有した磁気インピーダンス効果素子でもよい。
【０１２０】
なお、感磁部３５、４５、５５、６７、及び７４の両端部に、感磁部の素子長手方向（Ｙ方向）に駆動交流電流を与えるための電極部が、Ｃｕ、Ｎｉ、Ｔｉ、Ｃｒなどの導電性材料により形成される。感磁部３５、４５、５５、６７、及び７４は、略長方形状または線状にパターン形成されている。または、感磁部３５、４５、５５、６７、及び７４は、Ｕ字形状またはジグザグ状に形成されてもよい。
【０１２１】
感磁部３５、４５、５５、６７、及び７４の素子長手方向（Ｙ方向）に駆動交流電流を与え、素子幅方向（Ｘ方向）に励磁する。この状態で、外部磁界Ｈｅｘが素子長手方向に印加されると、感磁部３５、４５、５５、６７、及び７４のインピーダンスが変化する。感磁部３５、４５、５５、６７、及び７４のインピーダンス変化を、電極部間の電圧の変化として取り出す。
【０１２２】
なお、感磁部３５、４５、５５、６７、及び７４上に、絶縁材料からなる保護層が形成されてもよい。
【０１２３】
図７は、参考例の磁気インピーダンス効果素子の斜視図であり、図８は、図７の磁気インピーダンス効果素子を８−８線からみた断面図である。
【０１２４】
図７及び図８の磁気インピーダンス効果素子では、アルミナチタンカーバイドなどの非磁性材料からなる基板２１上に、軟磁性薄膜８１、絶縁性材料からなる絶縁層８２、導電性薄膜８３、絶縁層８４、軟磁性薄膜８５が順次積層されて感磁部８６が形成されている。
【０１２５】
軟磁性薄膜８１と導電性薄膜８３は、絶縁層８２によって電気的に絶縁されている。また、導電性薄膜８３と軟磁性薄膜８５は、絶縁層８４によって電気的に絶縁されている。
【０１２６】
感磁部８６の両端部には、導電性薄膜８３の素子長手方向（Ｙ方向）に駆動交流電流を与えるための電極部８７，８７が、Ｃｕ、Ｎｉ、Ｔｉ、Ｃｒなどの導電性材料により形成される。電極部８７，８７は導電性薄膜８３にのみ接続されている。軟磁性薄膜８１と電極部８７，８７は、絶縁層８２によって電気的に絶縁されている。また、軟磁性薄膜８５と電極部８７，８７は、絶縁層８４によって電気的に絶縁されている。従って、駆動交流電流は導電性薄膜８３のみに流される。
【０１２７】
導電性薄膜８３の素子長手方向（Ｙ方向）に駆動交流電流を与え、素子幅方向（Ｘ方向）に励磁する。この状態で、外部磁界Ｈｅｘが素子長手方向に印加されると、感磁部８６のインピーダンスが変化する。感磁部８６のインピーダンス変化を、電極部間の電圧の変化として取り出す。
【０１２８】
駆動交流電流が導電性薄膜８３のみに流され、軟磁性薄膜８１，８５には流されないようにすると、駆動交流電流による励磁磁界を効率よく発生させることができ、より顕著な磁気インピーダンス効果を引き出すことが可能になる。
【０１２９】
感磁部８６は、略長方形状または線状にパターン形成されている。または、感磁部８６は、Ｕ字形状またはジグザグ状に形成されてもよい。
【０１３０】
図９は、磁気インピーダンス効果素子の感磁部のアスペクト比と、磁界検出感度の関係を示すグラフである。図９のグラフでは、感磁部の素子長さＬを４ｍｍまたは６ｍｍに固定し、素子幅Ｗを変えることにより感磁部のアスペクト比Ｗ／Ｌを変化させた。図９から明らかなように、感磁部のアスペクト比Ｗ／Ｌが０．１以下になると、磁気インピーダンス効果素子の磁界検出感度が向上することがわかる。特に、感磁部の素子長さＬが６ｍｍのときには、感磁部のアスペクト比Ｗ／Ｌが約０．０８以下になると、さらに、急激に磁気インピーダンス効果素子の磁界検出感度が向上することがわかる。
【０１３１】
なお、感磁部がＵ字型、つづら折れ状に形成される場合には、前記感磁部の素子長手方向を向いた部位の長さの総和が素子長さＬとなる。
【０１３２】
本実施の形態では、感磁部２５は、例えば、素子幅Ｗを０．１０ｍｍ、素子長さＬを６ｍｍとして形成されている。このとき、磁気インピーダンス効果素子Ｍの感磁部２５のアスペクト比は、Ｗ／Ｌ＝０．０１７である。
【０１３３】
図１に示された磁気インピーダンス効果素子Ｍの、素子長さ６ｍｍ、アスペクト比が０．０１７であると、図９のグラフから、約２．５（ｍＶ・ｍ／Ａ）（約２００（ｍＶ／Ｏｅ））もの高感度を有することがわかる。
【０１３４】
図１０は、磁気インピーダンス効果素子の感磁部のアスペクト比（Ｗ／Ｌ）と、感磁部の両端からの出力電圧を最大とする外部磁界の大きさの絶対値（Ｈｐ）との関係を示すグラフである。
【０１３５】
図１０のグラフから、磁気インピーダンス効果素子の感磁部のアスペクト比（Ｗ／Ｌ）を小さくすると、感磁部の両端からの出力電圧を最大とする外部磁界の大きさの絶対値（Ｈｐ）も小さくなることがわかる。図３のグラフでは、感磁部の素子長さを４ｍｍまたは６ｍｍに固定し、素子幅を変えることにより感磁部のアスペクト比を変化させている。
【０１３６】
例えば、感磁部の素子長さが６ｍｍのとき、アスペクト比（Ｗ／Ｌ）を約０．１以下にすると、感磁部の両端からの出力電圧を最大とする外部磁界の大きさの絶対値（Ｈｐ）の値は、３２０（Ａ／ｍ）（４（Ｏｅ））以下になる。また、感磁部の素子長さが４ｍｍのときも、アスペクト比（Ｗ／Ｌ）を約０．１以下にすると、出力電圧を最大とする外部磁界の大きさの絶対値（Ｈｐ）が、３２０（Ａ／ｍ）（４（Ｏｅ））以下になる。
【０１３７】
また、感磁部の素子長さが６ｍｍのとき、アスペクト比（Ｗ／Ｌ）を約０．０５以下にすると、出力電圧を最大とする外部磁界の大きさの絶対値（Ｈｐ）が１６０（Ａ／ｍ）（２（Ｏｅ））以下になる。
【０１３８】
図１に示された本実施の形態の磁気インピーダンス効果素子Ｍの感磁部２５は、素子長さ６ｍｍ、アスペクト比が０．０１７であるので、図１０のグラフから、出力電圧を最大とする外部磁界の大きさの絶対値が、おおよそ０〜２４（Ａ／ｍ）（０．３（Ｏｅ））の範囲にあることがわかる。
【０１３９】
図１１は、本実施の形態の磁気インピーダンス効果素子の磁気インピーダンス効果特性を説明するための概念図である。
【０１４０】
図１の磁気インピーダンス効果素子Ｍの電極部２６，２６から感磁部２５の両端部に駆動交流電流を与えた状態で、外部磁界Ｈｅｘを、磁気インピーダンス効果素子Ｍの素子長手方向に印加する。印加した外部磁界Ｈｅｘの大きさを変化させつつ、出力電圧Ｅｍｉを測定すると図１１のようなグラフが得られる。
【０１４１】
図１１の磁気インピーダンス効果特性を示す概念図は、外部磁界Ｈｅｘの大きさがＨｐ₊あるいはＨｐ_-であるときの出力電圧Ｅｍｉの値を示す点を頂点とする双峰形状をなしている。また、Ｈｐ₊とＨｐ_-の絶対値の大きさはほとんど等しくおおよそ０〜２４（Ａ／ｍ）（０．３（Ｏｅ））である。
【０１４２】
図１１をみると、外部磁界Ｈｅｘの大きさがＨｐ₊またはＨｐ_-に近づくにつれて、出力電圧Ｅｍｉの変化率が大きくなっている。すなわち、外部磁界Ｈｅｘの検出感度は、外部磁界Ｈｅｘの大きさがＨｐ₊またはＨｐ_-付近にあるときに良好になる。
【０１４３】
Ｈｐ₊またはＨｐ_-の大きさの絶対値がおおよそ０〜２４（Ａ／ｍ）（０．３（Ｏｅ））であるとき、外部磁界Ｈｅｘ＝０付近における外部磁界Ｈｅｘの検出感度を良好にするために、感磁部２５の素子長手方向に印加するバイアス磁界の大きさは、例えば、Ｈ_B＝０〜８０（Ａ／ｍ）（１（Ｏｅ））であれば充分である。なお、後述する実施例において、磁気インピーダンス効果素子の、実測値に基づいた磁気インピーダンス効果特性のグラフについて説明する。
【０１４４】
なお、Ｈｐ₊またはＨｐ_-の大きさの絶対値が４００（Ａ／ｍ）（５（Ｏｅ））以下、好ましくは３２０（Ａ／ｍ）（４（Ｏｅ））以下、より好ましくは１６０（Ａ／ｍ）（２Ｏｅ）以下であれば、感磁部２５の素子長手方向に印加するバイアス磁界の大きさを４００（Ａ／ｍ）（５（Ｏｅ））以下、好ましくは３２０（Ａ／ｍ）（４（Ｏｅ））以下、より好ましくは１６０（Ａ／ｍ）（２Ｏｅ）以下にできる。
【０１４５】
感磁部２５の素子長手方向に印加する必要なバイアス磁界の大きさを、４００（Ａ／ｍ）以下にすることができると、感磁部２５の周辺に形成された硬磁性材料や、或いは感磁部２５に重ねて形成された硬磁性材料や反強磁性材料からなる磁性膜から発生する磁界を、バイアス磁界として用いることが可能になる。
【０１４６】
また、感磁部２５の素子長手方向に印加するバイアス磁界の大きさを４００（Ａ／ｍ）（５（Ｏｅ））以下、好ましくは３２０（Ａ／ｍ）（４（Ｏｅ））以下、より好ましくは１６０（Ａ／ｍ）（２Ｏｅ）以下にできると、感磁部２５にバイアス磁界を与えるために、感磁部２５の周囲に巻回するコイルの巻回数も少なくなり、磁気インピーダンス効果素子を製造する際の工程を簡略化することができるようになる。また、磁気インピーダンス効果素子Ｍを磁気ヘッドや微弱磁界検出器に適用する際に必要な小型化も容易になる。さらに、バイアス磁界を発生させるためにコイルに与える直流電流も小さくすることができるので、磁気インピーダンス効果素子Ｍの省電力化も容易になる。
【０１４７】
磁気インピーダンス効果素子の感磁部の素子幅Ｗと素子長さＬの比（アスペクト比）Ｗ／Ｌを小さくしていくと、磁気インピーダンス効果素子の磁界検出感度が向上するという効果が得られるのは以下の理由による。
【０１４８】
前記感磁部は高周波数の交流電流によって励磁されるので、表皮効果が強く現れる。このとき、前記感磁部の素子幅Ｗ、素子長さＬ、比抵抗ρ、励磁周波数ω、素子幅方向の透磁率μと前記感磁部のインピーダンスの大きさ｜Ｚ｜との間には、次の（数２）によって示される関係がある。
【０１４９】
【数２】

（数２）から、前記感磁部の素子幅Ｗ、素子長さＬ、比抵抗ρ、励磁周波数ωを一定としたとき、前記感磁部のインピーダンスの大きさ｜Ｚ｜は、素子幅方向の透磁率μの１／２乗に比例することがわかる。
【０１５０】
素子長手方向に交流電流が与えられ、素子幅方向に励磁されている前記感磁部の素子長手方向に、外部磁界が印加されると、前記感磁部の素子幅方向の透磁率μが変化し、前記感磁部のインピーダンスの大きさ｜Ｚ｜が変化する。前記感磁部のインピーダンスの大きさ｜Ｚ｜の変化を測定することにより、前記感磁部に印加された外部磁界を検知する。
【０１５１】
アスペクト比Ｗ／Ｌが小さくなると、素子幅方向の透磁率μの変化に対するインピーダンスの大きさ｜Ｚ｜の変化率が大きくなる。すなわち、前記感磁部の両端から引き出される出力電圧の大きさの変化が大きくなり、磁気インピーダンス効果素子の磁界検出感度が向上する。
【０１５２】
図１２は、磁気インピーダンス効果素子の感磁部を構成する軟磁性薄膜の、磁区構造の一例を示す概念平面図である。
【０１５３】
図１２では、図１に示された磁気インピーダンス効果素子Ｍの感磁部２５を構成する軟磁性薄膜２２，２４のうち、軟磁性薄膜２２の磁区構造を示しているが、軟磁性薄膜２４の磁区構造も、軟磁性薄膜２２の磁区構造とほぼ同様である。軟磁性薄膜２２は、静磁場中で形成され、あるいは、異方性の強い軟磁性材料を用いて形成されることにより、素子幅方向の磁気異方性を持たされている。したがって、素子幅方向に磁気モーメントが配向している磁区２２ａが形成されている。なお、図１２の軟磁性薄膜２２の素子幅をＷ１とする。
【０１５４】
一方、形状磁気異方性により軟磁性薄膜２２の素子長手方向に磁気モーメントが配向している磁区２２ｂが形成される。
【０１５５】
軟磁性薄膜２２のアスペクト比が大きいと、素子長手方向に磁気モーメントが配向している磁区２２ｂの総面積が、素子幅方向に磁気モーメントが配向している磁区２２ａの総面積よりも、著しく狭くなる。
【０１５６】
図１３は、磁気インピーダンス効果素子Ｍの軟磁性薄膜２２の他の磁区構造を示す平面概念図である。
【０１５７】
例えば、軟磁性薄膜２２の素子幅をＷ１より小さいＷ２にすることによって、軟磁性薄膜２２のアスペクト比を０．１より小さくする。
【０１５８】
図１３において、磁区２２ｂは、磁気モーメントの素子長手方向の成分と素子幅方向の成分を比較したときに、前記素子長手方向の成分の方が大きい磁区であり、磁区２２ａは、前記素子幅方向の成分の方が大きい磁区である。図１３において、磁区２２ｂの総面積は、図１２の磁区２２ｂの総面積とほとんど変わらず、磁区２２ａの総面積は、図１２の磁区２２ａの総面積より減少し、磁区２２ａと磁区２２ｂの総面積の値が等しくなっている。すると、軟磁性薄膜２２の全体としての磁気異方性の方向がほぼ等方的な状態になる。
【０１５９】
素子長手方向の成分の方が大きい磁区である磁区２２ｂの総面積と、前記素子幅方向の成分の方が大きい磁区である磁区２２ａの総面積が拮抗すると、すなわち、素子幅方向と素子長手方向の磁気異方性エネルギーがつり合うと、軟磁性薄膜２２は、磁気異方性の方向が全体としてほぼ等方的な状態になる。つまり、軟磁性薄膜２２の磁気モーメントはある方向に固定されにくくなり、交流電流によって励磁されたときに磁気モーメントの方向を変化させやすくなっている。すなわち、軟磁性薄膜２２の素子幅方向の透磁率μは増加している。
【０１６０】
軟磁性薄膜２２の素子幅方向の透磁率μが最大値をとるとき、軟磁性薄膜２２のインピーダンスの大きさＺが最大となり、軟磁性薄膜２２の両端からの出力電圧も最大になる。
【０１６１】
図１３では、外部磁界を印加していないときに、軟磁性薄膜２２は磁気異方性の方向が全体として等方的な状態に近い状態にされている。
【０１６２】
従って、軟磁性薄膜２２の素子長手方向に、外部磁界Ｈｅｘを印加しなくとも、或いはわずかに外部磁界Ｈｅｘを印加するだけで、軟磁性薄膜２２の磁気異方性の方向を全体としてほぼ等方的な状態にさせ、軟磁性薄膜２２の素子幅方向の透磁率μを最大にさせることができ、さらに軟磁性薄膜２２の両端からの出力電圧Ｅｍｉを最大にさせることができる。
【０１６３】
すなわち、駆動交流電流が与えられている軟磁性薄膜２２に外部磁界Ｈｅｘを印加したときに、軟磁性薄膜２２からの出力電圧Ｅｍｉを最大とする外部磁界Ｈｅｘの大きさの絶対値Ｈｐを小さくさせることができる。
【０１６４】
なお、軟磁性薄膜２２が単磁区構造を有し、各磁区において磁気モーメントの素子長手方向の成分と素子幅方向の成分が釣り合っていてもよい。
【０１６５】
また、本発明の磁気インピーダンス効果素子では、図１４に示されるように、素子長手方向の成分の方が大きい磁区である磁区２２ｂの総面積が、前記素子幅方向の成分の方が大きい磁区である磁区２２ａの総面積より大きい場合においても、軟磁性薄膜２２の磁気異方性の方向を全体として等方的な状態に近い状態にすることができ、磁区２２ｂの総面積と磁区２２ａの総面積とが拮抗している磁区構造の軟磁性薄膜２２を有する磁気インピーダンス効果素子と同等の磁界検出感度を得ることができる。
【０１６６】
また、本実施の形態の磁気インピーダンス効果素子では、磁界検出感度を、少なくとも磁界センサとして実用可能な範囲である０．３（ｍＶ・ｍ／Ａ）（２５ｍＶ／Ｏｅ）以上にすることができる。
【０１６７】
また、感磁部２５の両端からの出力電圧を最大にさせる外部磁界の大きさの絶対値を小さくさせることができる。
【０１６８】
図１５から図１７は、本発明の磁気インピーダンス効果素子の実施の形態として、バイアス磁界を薄膜磁性体によって与えることのできる磁気インピーダンス効果素子の縦断面図である。
【０１６９】
図１５の磁気インピーダンス効果素子は、基板２１上に軟磁性薄膜９１、導電性薄膜９２、軟磁性薄膜９３からなる感磁部９４が形成され、感磁部９４の素子長手方向の両端部に電極９５，９５が形成され、さらに、感磁部９４の両端部に接触する磁性薄膜である硬磁性体層９６，９６が設けられたものである。硬磁性体層９６，９６は、ＣｏＰｔなどの硬磁性材料によって形成される。
【０１７０】
硬磁性体層９６，９６によって与えることのできるバイアス磁界の大きさは、最大で４００Ａ／ｍ程度であるが、本実施の形態の磁気インピーダンス効果素子では、感磁部９４の素子長手方向に印加する必要なバイアス磁界の大きさを、４００（Ａ／ｍ）以下にすることができるので、図１５のような硬磁性体層９６，９６によって、感磁部９４に十分なバイアス磁界をかけることができる。すなわち、バイアス磁界を与えるために直流電流が流される巻線コイルを用いなくてすむので、磁気インピーダンス効果素子の小型化・低消費電力化を達成できる。
【０１７１】
また、図１６に示されるように、硬磁性体層９６，９６が、感磁部９４の素子長手方向の両端部に形成され、硬磁性体層９６，９６上に電極９５，９５が形成されてもよい。
【０１７２】
あるいは、図１７に示されるように、感磁部９４の上層及び下層に反強磁性層９７，９７を積層し、感磁部９４の軟磁性薄膜９１，９３と反強磁性層９７，９７との界面に生じる交換異方性磁界によって、感磁部９４に必要なバイアス磁界を与えることも可能である。
【０１７３】
図１８及び図１９は、図１の磁気インピーダンス効果素子の製造方法を説明するための斜視図である。
【０１７４】
図１８は、アルミナチタンカーバイド、ガラス、セラミック、結晶化ガラスなどの非磁性材料からなる基板２１上に、軟磁性薄膜２２、導電性薄膜２３及び軟磁性薄膜２４を順次スパッタ法、蒸着法或いはメッキ法などによって成膜し、積層した状態を示す斜視図である。
【０１７５】
軟磁性薄膜２２及び２４は、例えば、組成式がＦｅ_71.4Ａｌ_5.8Ｓｉ_13.1Ｈｆ_3.3Ｃ_4.5Ｒｕ_1.9で表される、ｂｃｃ−Ｆｅの結晶粒を主体とした微結晶軟磁性合金薄膜である。
【０１７６】
この組成以外のＴ―Ｘ―Ｍ―Ｚ―Ｑ系（元素Ｔは、Ｆｅ、Ｃｏのうちどちらか一方あるいは両方を含む元素であり、元素Ｘは、Ｓｉ、Ａｌの内どちらか一方あるいは両方を含む元素であり、元素Ｍは、Ｔｉ、Ｚｒ、Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｍｏ，Ｗから選ばれる１種または２種以上の元素であり、元素Ｚは、Ｃ、Ｎのうちどちらか一方あるいは両方を含む元素であり、Ｑは、Ｃｒ，Ｒｅ，Ｒｕ，Ｒｈ，Ｎｉ，Ｐｄ，Ｐｔ，Ａｕから選ばれる１種または２種以上の元素）の微結晶軟磁性合金薄膜や、Ｃｏ−Ｔ−Ｍ−Ｘ―Ｏ系（元素Ｔは、Ｆｅ、Ｎｉのうちどちらか一方あるいは両方を含む元素であり、元素Ｍは、Ｔｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｃｒ，Ｍｏ，Ｓｉ，Ｐ，Ｃ，Ｗ，Ｂ，Ａｌ，Ｇａ，Ｇｅと希土類元素から選ばれる１種または２種以上の元素であり、Ｘは、Ａｕ，Ａｇ，Ｃｕ，Ｒｕ，Ｒｈ，Ｏｓ，Ｉｒ，Ｐｔ，Ｐｄから選ばれる１種あるいは２種以上の元素）の組成を有し、ｂｃｃ−Ｆｅ、ｂｃｃ−ＦｅＣｏ、ｂｃｃ−Ｃｏ等からなる平均結晶粒径１０〜３０ｎｍの結晶相とＭの酸化物を含む非晶質相からなり、非晶質相が組織全体の５０％以上を占めている微結晶軟磁性合金薄膜や、Ｆｅ―Ｍ―Ｏ系（Ｍは、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｗと希土類元素から選ばれる１種あるいは２種以上の元素）の組成を有し、ｂｃｃ−Ｆｅを主体とする平均結晶粒径１０〜３０ｎｍの結晶相とＭの酸化物を含む非晶質相からなり、非晶質相が組織全体の５０％以上を占めている微結晶軟磁性合金薄膜として、軟磁性薄膜２２及び２４が形成されていてもよい。
【０１７７】
あるいは、Ｃｏ―Ｔａ―Ｈｆ系の非晶質軟磁性合金薄膜や、Ｃｏ−Ｚｒ−Ｎｂ系の非晶質軟磁性合金薄膜として、軟磁性薄膜２２及び２４を形成してもよい。
【０１７８】
導電性薄膜２３は、Ｃｕ、Ｎｉ、Ｔｉ、Ｃｒなどの導電性材料により形成される。また、導電性薄膜２３を形成するために用いる材料は、軟磁性薄膜２２，２４より比抵抗の低い材料であれば、どのようなものでもかまわない。例えば、Ｆｅ，Ｃｏを含む強磁性材料であっても、ＮｉＯ，ＣｏＯなどの反強磁性材料であってもよい。ただし、導電性薄膜２３を形成するために用いる材料の比抵抗は、軟磁性薄膜２２，２４を形成するために用いる材料の比抵抗の１／１０以下の比抵抗の材料であることが好ましい。
【０１７９】
なお、本実施の形態では、軟磁性薄膜２２、導電性薄膜２３、及び軟磁性薄膜２４の成膜をＲＦマグネトロンスパッタ装置を用いて行った。成膜時の条件は以下の範囲である。
【０１８０】
高周波電力：２００〜４００（Ｗ）
Ａｒガス圧：５０（ｓｃｃｍ）
成膜時圧力：３〜７（ｍＴｏｒｒ）
成膜時静磁場強度：７９０以上（Ａ／ｍ）
成膜速度：１０〜３３．５（ｎｍ／分）
なお、標準条件は、高周波電力が４００（Ｗ）、Ａｒガス圧が５０（ｓｃｃｍ）、成膜時圧力が７（ｍＴｏｒｒ）、成膜時静磁場強度が４７４０（Ａ／ｍ）、成膜速度が３３．５（ｎｍ／分）である。また、基板の冷却は間接冷却によって行った。
【０１８１】
次に、軟磁性薄膜２２、導電性薄膜２３、及び軟磁性薄膜２４をフォトリソグラフィーおよびエッチングによって、図１９に示されるようにパターン形成して感磁部２５を形成する。このとき、感磁部２５を素子幅Ｗと素子長さＬの比Ｗ／Ｌ（アスペクト比）が、０．１以下になるように略長方形にパターン形成する。
【０１８２】
感磁部２５は、例えば、素子幅Ｗを１００μｍ、素子長さＬを６ｍｍとして形成される。したがって、本実施の形態の磁気インピーダンス効果素子Ｍの感磁部２５のアスペクト比は、Ｗ／Ｌ＝０．０１７である。
【０１８３】
なお、感磁部２５は、基板２１上一面に形成されるが、図６ではそのうち一部のみを示している。
【０１８４】
本実施の形態では、感磁部２５をパターン形成した後、感磁部２５の素子幅方向に静磁場Ｈ２をかけ、熱処理にかける。
【０１８５】
なお、軟磁性薄膜２２及び軟磁性薄膜２４を成膜するときに、図１の磁気インピーダンス効果素子が完成したときに素子幅方向となる図１８の矢印方向に静磁場Ｈ１をかけてもよい。このように磁場中成膜を行なったときには、成膜後の静磁場中熱処理の工程を省略することが可能である。または、磁場中成膜後に、静磁場中熱処理の代りに回転磁場中、または無磁場中熱処理を行なってもよい。
【０１８６】
静磁場中熱処理、あるいは回転磁場中または無磁場中熱処理の条件は、以下の範囲である。
【０１８７】
静磁場強度：０〜７９０００（Ａ／ｍ）
熱処理温度：５４０〜６７５（℃）
熱処理時間：２０〜３０（分）
昇温レート：１０〜１４（℃／分）
なお、標準条件は、静磁場強度が７９０００（Ａ／ｍ）、熱処理温度が５７５（℃）、熱処理時間が３０（分）、昇温レートが１３．６（℃／分）である。
【０１８８】
なお、本実施の形態では、図１８のように軟磁性薄膜２２、導電性薄膜２３、及び軟磁性薄膜２４を順次成膜した後に、図１９のように、感磁部２５をパターン形成した後で、静磁場中熱処理を施しているが、軟磁性薄膜２２、導電性薄膜２３、及び軟磁性薄膜２４の成膜後、感磁部２５をパターン形成する前、すなわち、図１８の状態で、静磁場中熱処理を施し、その後、感磁部２５をパターン形成してもよい。
【０１８９】
静磁場中、回転磁場中、または無磁場中での熱処理は、前記軟磁性薄膜の素子長手方向に発生する形状磁気異方性と素子幅方向の磁気異方性とをほぼ拮抗させ、前記感磁部の磁気異方性の方向を全体としてほぼ等方的な状態にさせるために行われる。
【０１９０】
すなわち、前記磁場中成膜及び熱処理工程は、アスペクト比Ｗ／Ｌを小さくさせたときにおいても、素子幅方向の透磁率μを高く維持するために行われるのであり、単に軟磁性薄膜の素子幅方向に磁気異方性を持たせるためだけのものではない。
【０１９１】
感磁部２５をパターン形成し、磁場中熱処理を施した後に、図１のように、感磁部２５の両端部に、Ｃｕ、Ｎｉ、Ｔｉ、Ｃｒなどの導電性材料からなる電極部２６，２６をスパッタ法、フォトリソグラフィー、およびエッチングによって形成する。
【０１９２】
電極部２６，２６を形成後、基板２１を切断し、図１のような個々の磁気インピーダンス効果素子Ｍとする。
【０１９３】
図２のような磁気インピーダンス効果素子を製造するときは、基板２１上に軟磁性薄膜３２、導電性薄膜３３をパターン形成し、その後、軟磁性薄膜３４を成膜して、軟磁性薄膜３２と軟磁性薄膜３４とが素子幅方向の両端部で磁気的に接続されるようにする。
【０１９４】
図３のような磁気インピーダンス効果素子を製造するときには、アルミナチタンカーバイド、ガラス、セラミック、結晶化ガラスなどの非磁性材料からなる基板２１上に、軟磁性薄膜４２、導電性薄膜４３及び軟磁性薄膜４４を順次スパッタ法、蒸着法或いはメッキ法などによって成膜して、図１８と同様の多層膜を形成した後、軟磁性薄膜４４上にフォトレジストを積層する。前記フォトレジストは形成される感磁部４５と同じ形状、同じ大きさで形成する。例えば、幅１００μｍ、長さ６ｍｍの略長方形状で形成する。
【０１９５】
次に、フッ酸、過酸化水素水などを含む酸性水溶液を用いて、前記フォトレジストが積層された多層膜にエッチング処理を施すことにより、感磁部４５をパターン形成する。このエッチング処理により、感磁部４５を、基板２１の表面から離れるにつれて、素子幅方向（Ｘ方向）寸法が徐々に短くなるもの、すなわち図３のように素子幅方向の両端部にテーパー面４５ｃ、４５ｃが形成されたものとして形成することができる。
【０１９６】
また、図７及び図８に示された磁気インピーダンス効果素子を製造するときには、基板２１上に軟磁性薄膜８１をパターン形成した後、絶縁層８２、導電性薄膜８３、絶縁層８４を順次積層し、導電性薄膜８３のみと電気的に接続される電極部８７，８７を形成すればよい。
【０１９７】
なお、図１９では、磁気インピーダンス効果素子の感磁部２５は、導電性薄膜２３の上下に軟磁性薄膜２２と軟磁性薄膜２４とが積層された構造であるが、軟磁性薄膜２４上にさらに導電性薄膜及び軟磁性薄膜を積層する工程を繰り返し行なってもよい。
【０１９８】
なお、図２から図８に示された磁気インピーダンス効果素子を製造する際にも、感磁部３５，４５，５５，６７，７４，８６を形成した後、感磁部３５，４５，５５，６７，７４，８６の素子幅方向に静磁場をかける。
【０１９９】
なお、感磁部３５，４５，５５，６７，７４，８６に含まれる軟磁性薄膜を成膜するときに、感磁部の素子幅方向となる方向に静磁場をかけてもよい。このように磁場中成膜を行なったときには、成膜後の静磁場中熱処理の工程を省略することが可能である。または、磁場中成膜後に、静磁場中熱処理の代りに回転磁場中、または無磁場中熱処理を行なってもよい。
【０２００】
また、感磁部２５，３５，４５，５５，６７，７４，８６をＵ字型もしくはつづら折れ状にパターン形成してもよい。感磁部２５，３５，４５，５５，６７，７４，８６がＵ字型、つづら折れ状に形成される場合には、感磁部２５，３５，４５，５５，６７，７４，８６の素子長手方向を向いた部位の長さの総和が素子長さＬとなる。感磁部２５，３５，４５，５５，６７，７４，８６がＵ字型やつづら折れ形状で形成されているときは、感磁部２５，３５，４５，５５，６７，７４，８６の中のもっとも長い直線部分の延長方向が素子長手方向となり、この方向が駆動交流電流によって発生する磁界の励磁方向に対して垂直な方向に一致する。
【０２０１】
感磁部２５，３５，４５，５５，６７，７４，８６は、例えば、素子幅Ｗを０．１０ｍｍ、素子長さＬを６ｍｍとして形成される。このとき、磁気インピーダンス効果素子の感磁部２５，３５，４５，５５，６７，７４，８６のアスペクト比は、Ｗ／Ｌ＝０．０１７である。
【０２０２】
このとき、磁気インピーダンス効果素子の形成後、感磁部２５，３５，４５，５５，６７，７４，８６の素子長手方向に、駆動交流電流を与えつつ外部磁界を印加したときに、感磁部２５，３５，４５，５５，６７，７４，８６の両端からの出力電圧を最大とする外部磁界の大きさの絶対値は、４００（Ａ／ｍ）以下になる。
【０２０３】
感磁部２５，３５，４５，５５，６７，７４，８６の成膜を、静磁場中で行わせることにより、感磁部２５，３５，４５，５５，６７，７４，８６に含まれる軟磁性薄膜の、素子長手方向（Ｘ方向）の形状磁気異方性エネルギーと素子幅方向（Ｙ方向）の磁気異方性エネルギーとをほぼつり合わせることができる。すなわち、図１３に示されるように、素子長手方向の成分の方が大きい磁区である磁区２２ｂの総面積が、前記素子幅方向の成分の方が大きい磁区である磁区２２ａの総面積に等しい磁区構造を有するもの、あるいは、図１４に示されるように、素子長手方向の成分の方が大きい磁区である磁区２２ｂの総面積が、前記素子幅方向の成分の方が大きい磁区である磁区２２ａの総面積より大きい磁区構造を持つものが得られる。
【０２０４】
図２０は、本実施の形態において用いられたＲＦマグネトロンスパッタ装置の内部構造を示す構成図である。
【０２０５】
図２０に示されるように、マグネトロンスパッタ装置１０１のチャンバー１０２内には、ターゲット１０３、１０４を取り付けるための電極部１０５と、ターゲット１０３、１０４と対向する位置に、基板保持部１０６とが設けられている。なお基板保持部１０６上には、基板２１が置かれている。
【０２０６】
ターゲット１０３は軟磁性材料、ターゲット１０４は導電性材料からなっている。また、ターゲット１０３とターゲット１０４の間には遮蔽板１０７が設けられている。
【０２０７】
電極部１０５内には、放電用磁石（図示せず）が設けられており、この放電用磁石から発生する磁場によって、ターゲット１０３、１０４の表面には、エロージョン領域（図示しない）が形成される。
【０２０８】
また、チャンバー１０２には、ガス導入口１０８と、ガス排気口１０９とが設けられており、ガス導入口１０８からＡｒ（アルゴン）ガスが導入される。
【０２０９】
電極部１０５に、高周波電源（ＲＦ電源）１１０から高周波が印加されることによって、電場と磁場の相互作用により、マグネトロン放電が発生し、ターゲット１０３及び１０４がスパッタされる。
【０２１０】
薄膜が積層される基板２１が軟磁性材料からなるターゲット１０３の下の領域Ａにあるときには、軟磁性薄膜が成膜され、導電性材料からなるターゲット１０４の下の領域Ｂにあるときには、導電性薄膜が成膜される。
【０２１１】
まず、軟磁性材料からなるターゲット１０３の下の領域Ａに基板２１を配置する。基板保持部１０６は、矢印方向に回転している。基板保持部１０６が回転することによって、基板２１上に軟磁性薄膜２２が成膜されながら、基板２１が非磁性材料からなるターゲット１０４の下の領域Ｂに移動し、軟磁性薄膜２２上に導電性薄膜２３が成膜される。基板保持部１０６はさらに回転し続けて、基板２１は再びターゲット１０３の下の領域Ａに移動し、導電性薄膜２３上に軟磁性薄膜２４が成膜されて、図１８の状態になる。
【０２１２】
さらに、ＲＦマグネトロンスパッタ装置を稼動し続け、基板保持部１０６を回転させ続けることにより、導電性薄膜と軟磁性薄膜を任意の層数だけ積層することができる。
【０２１３】
なお、磁場中成膜を行なう場合には、基板保持部１０６を挟んで、成膜中の軟磁性薄膜に静磁場をかけるための磁石を設置する。前記磁石は、例えば、Ｓｍ−Ｃｏなどの硬磁性材料または電磁石などによって形成されている。
【０２１４】
なお、スパッタ装置としては、図２０に示すようなＲＦマグネトロンスパッタ装置１０１以外に、ＲＦ２極スパッタ装置、ＲＦ３極スパッタ装置、イオンビームスパッタ装置、または対向ターゲット式スパッタ装置など既存のものを任意に使用してよい。
【０２１５】
また、本発明における軟磁性薄膜、導電性薄膜の成膜方法には、スパッタ法の他に蒸着法、ＭＢＥ（モレキュラー−ビーム−エピタキシー）法、ＩＣＢ（イオン−クラスター−ビーム）法またはメッキ法などを使用してもよい。
【０２１６】
また、感磁部２５を、軟磁性薄帯を用いて形成する場合には、例えば、図２１に示す液体急冷装置Ｃを用いる。
【０２１７】
まず、Ｆｅ−Ｃｏ−Ｓｉ−Ｂ系の軟磁性材料が、石英からなるノズル１１１に投入され、ノズル１１１の周囲に設けられたヒータ１１２により加熱され、溶融される。この溶融合金１１３をノズルの上部から加えられた圧力により高速回転している冷却ロール１１４上に射出させて接触急冷することにより、軟磁性薄帯１１５を形成する。
【０２１８】
得られた軟磁性薄帯１１５を素子幅Ｗと素子長さＬの比（アスペクト比）Ｗ／Ｌが、０．１以下になるように、略長方形に切断する。この軟磁性薄帯１１５の少なくとも一方の面に、導電性薄膜を、スパッタ、蒸着などの方法により形成する。
【０２１９】
次に、基板上に順次前記導電性薄膜を積層した軟磁性薄帯を少なくとも２枚以上接着積層して感磁部を形成した後、この感磁部を素子幅方向の静磁場中で熱処理にかける。
【０２２０】
さらに、前記感磁部の両端部に電極部を形成すると、図１のような磁気インピーダンス効果素子が得られる。
【０２２１】
図２２から図２５は、図１の磁気インピーダンス効果素子の感磁部２５の軟磁性薄膜２４をカー効果偏光顕微鏡によって観察し、写真撮影したものの摸式図である。
【０２２２】
図２２は、感磁部２５を素子長手方向（Ｘ方向）の長さＬ＝２ｍｍ、素子幅方向（Ｙ方向）の長さＷ＝１００μｍ、すなわちアスペクト比Ｗ／Ｌ＝０．０５として形成したもの軟磁性薄膜２４の磁区構造を示している。また、図２３及び図２４は、感磁部２５を素子長手方向の長さＬ＝４ｍｍ、素子幅方向寸法Ｗ＝１００μｍ、すなわちアスペクト比Ｗ／Ｌ＝０．０２５として形成したもの軟磁性薄膜２４の磁区構造を示している。
【０２２３】
図２２及び図２３では、素子幅方向に磁気モーメントが配向している磁区の総面積と、素子長手方向に磁気モーメントが配向している磁区の総面積が拮抗している状態になっており、素子幅方向と素子長手方向の磁気異方性エネルギーがつり合って、磁気異方性の方向が全体としてほぼ等方的な状態になっている。
【０２２４】
また、図２４では、素子長手方向に磁気モーメントが配向している磁区の総面積が、素子幅方向に磁気モーメントが配向している磁区の総面積より大きくなっている。しかし、素子幅方向と素子長手方向の磁気異方性エネルギーがつり合って、磁気異方性の方向が全体としてほぼ等方的な状態になっている。
【０２２５】
つまり、図２２から図２４に示されたいずれの軟磁性薄膜２４においても、磁気モーメントはある方向に固定されにくくなり、交流電流によって励磁されたときに磁気モーメントの方向を変化させやすくなっている。すなわち、感磁部２５の素子幅方向の透磁率μは増加しており、磁気インピーダンス効果素子の磁界検出感度が大きくなっている。また、感磁部２５の両端からの出力電圧を最大にさせる外部磁界の大きさの絶対値を小さくさせることができ、必要なバイアス磁界の大きさを小さくできる。
【０２２６】
図２５は、感磁部を素子長手方向（Ｘ方向）の長さＬ＝４ｍｍ、素子幅方向（Ｙ方向）の長さＷ＝５００μｍ、すなわちアスペクト比Ｗ／Ｌ＝０．１２５として形成したものの軟磁性薄膜２４の磁区構造を示している。
【０２２７】
図２５では、素子幅方向に磁気モーメントが配向している磁区が大勢を占めており、磁気異方性の方向が素子幅方向を向いている。
【０２２８】
すなわち、感磁部の素子幅方向の透磁率μは小さく、磁気インピーダンス効果素子の磁界検出感度は小さい。また、感磁部の両端からの出力電圧を最大にさせる外部磁界の大きさの絶対値も大きく、必要なバイアス磁界も大きくなる。
【０２２９】
なお、図２２から図２５のいずれの感磁部も、ＦｅＡｌＳｉＨｆＣＲｕ系の組成を有し、ｂｃｃ−Ｆｅの結晶粒を主体とした微結晶軟磁性合金薄膜によって形成され、また感磁部の膜厚は４μｍで形成されている。
【０２３０】
また、図２２から図２５では、図１の磁気インピーダンス効果素子の感磁部２５の最上層の軟磁性薄膜２４の磁区構造を示したが、最下層の軟磁性薄膜２２も同様の磁区構造を示した。
【０２３１】
【実施例】
図２６及び図２７は、図１に示された磁気インピーダンス効果素子を用いて、磁気インピーダンス効果特性を測定した結果を示すグラフである。
【０２３２】
図２６の磁気インピーダンス効果素子Ｍの電極部２６，２６から感磁部２５の両端部に駆動交流電流を与えた状態で、外部磁界Ｈｅｘを、磁気インピーダンス効果素子Ｍの素子長手方向に印加する。印加した外部磁界Ｈｅｘの大きさを変化させつつ、出力電圧Ｅｍｉを測定した。
【０２３３】
図２６は、感磁部をＦｅＡｌＳｉＨｆＣＲｕ系の組成を有し、ｂｃｃ−Ｆｅの結晶粒を主体とした微結晶軟磁性合金薄膜によって形成し、感磁部２５の素子長手方向の長さを４ｍｍ、厚さを４μｍとし、素子幅方向寸法を変化させたときの結果である。
【０２３４】
図２６を見ると、感磁部２５の素子幅方向寸法が１０００μｍ（Ｗ／Ｌ＝０．２５）及び５００μｍ（Ｗ／Ｌ＝０．１２５）のときは、外部磁界の大きさを変化させたときに出力電圧の変化がほとんどみられず、磁界センサとして機能していないことが分かる。また、出力電圧を最大にさせる外部磁界の大きさの絶対値は、４００（Ａ／ｍ）を越えている。
【０２３５】
一方、感磁部２５の素子幅方向寸法が１００μｍ（Ｗ／Ｌ＝０．０２５）のときは、外部磁界の大きさを変化させたときに出力電圧の変化は、最大で２００ｍＶ以上となり、高感度な磁界センサとして機能することが分かる。また、出力電圧を最大にさせる外部磁界の大きさの絶対値は、１６０（Ａ／ｍ）である。
【０２３６】
なお、感磁部２５の素子幅方向寸法が１００μｍ（Ｗ／Ｌ＝０．０２５）のとき、感磁部２５を構成する軟磁性薄膜は単磁区構造或いは多磁区構造を有しており、各磁区において磁気モーメントの素子長手方向の成分と素子幅方向の成分を比較したときに、前記素子長手方向の成分の方が大きい磁区の総面積と、前記素子幅方向の成分の方が大きい磁区の総面積が等しいものであるか、または、前記素子長手方向の成分の方が大きい磁区の総面積が、前記素子幅方向の成分の方が大きい磁区の総面積より大きくなっている。
【０２３７】
図２７は、感磁部２５をＦｅＡｌＳｉＨｆＣＲｕ系の組成を有し、ｂｃｃ−Ｆｅの結晶粒を主体とした微結晶軟磁性合金薄膜によって形成し、感磁部２５の素子長手方向の長さを６ｍｍ、厚さを４μｍとし、素子幅方向寸法を変化させたときの結果である。
【０２３８】
図２７を見ると、感磁部２５の素子幅方向寸法が１０００μｍ（Ｗ／Ｌ＝０．１７）のときは、外部磁界の大きさを変化させたときに出力電圧の変化がほとんどみられず、磁界センサとして機能していないことが分かる。また、出力電圧を最大にさせる外部磁界の大きさの絶対値は、４００（Ａ／ｍ）を越えている。
【０２３９】
一方、感磁部２５の素子幅方向寸法が５００μｍ（Ｗ／Ｌ＝０．０８）のときは、外部磁界の大きさを変化させたときに出力電圧の変化は、最大で５０ｍＶ以上となり、磁界センサとして機能できることが分かる。また、出力電圧を最大にさせる外部磁界の大きさの絶対値は、３２０（Ａ／ｍ）である。さらに、感磁部２５の素子幅方向寸法が１００μｍ（Ｗ／Ｌ＝０．０１７）のときは、外部磁界の大きさを変化させたときに出力電圧の変化は、最大で６００ｍＶ以上となり、非常に高感度な磁界センサとして機能できることが分かる。また、出力電圧を最大にさせる外部磁界の大きさの絶対値は、０〜２４（Ａ／ｍ）である。
【０２４０】
なお、感磁部２５の素子幅方向寸法が５００μｍ又は１００μｍのとき、感磁部２５を構成する軟磁性薄膜は、単磁区構造或いは多磁区構造を有しており、各磁区において磁気モーメントの素子長手方向の成分と素子幅方向の成分を比較したときに、前記素子長手方向の成分の方が大きい磁区の総面積と、前記素子幅方向の成分の方が大きい磁区の総面積が等しいものであるか、または、前記素子長手方向の成分の方が大きい磁区の総面積が、前記素子幅方向の成分の方が大きい磁区の総面積より大きくなっている。
【０２４１】
図２８は、感磁部２５の素子長手方向の長さを３ｍｍに固定し、素子幅方向寸法を様々に変えた磁気インピーダンス効果素子を用いて、感磁部２５のアスペクト比と外部磁界を印加したときの出力電圧の変化量との関係を調べた結果を示すグラフである。
【０２４２】
図２８に示される出力電圧の変化量とは、外部磁界を３２０（Ａ／ｍ）変化させたときの電圧変化量である。
【０２４３】
磁気インピーダンス効果素子を磁界センサとして使用するときには、図２８のグラフにおける出力変化量を１００ｍＶ以上とすることが好ましい。したがって、感磁部のアスペクト比（Ｗ／Ｌ）を０．００４以上にすることが好ましいことがわかる。
【０２４４】
なお、図２８において出力変化量が最大値をとるときの、感磁部のアスペクト比は０．０１７である。
【０２４５】
【発明の効果】
以上、詳細に説明した本発明によれば、磁気インピーダンス効果素子の前記感磁部が、前記軟磁性体部と前記軟磁性体部よりも比抵抗の低い導電体部とが接した構造を有しているので、前記感磁部に駆動交流電流が与えられたときに、この駆動交流電流は前記軟磁性体部内を流れる電流と前記軟磁性体部内を流れる電流とに分れて流れ、前記駆動交流電流が流れるときの前記感磁部の直流抵抗値が低くなり、磁気インピーダンス効果素子の消費電力を小さくすることができる。
【０２４６】
また、本発明では、前記感磁部が透磁率の高い軟磁性体部と導電率の高い導電体部とが接した構造を有しているために、前記感磁部内を流れる駆動交流電流の表皮厚さが薄くなり、大きな磁気インピーダンス効果を発生させることができる。従って、低駆動電圧であっても磁界に対する充分な出力電圧の変化量を得ることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態を示す磁気インピーダンス効果素子の斜視図、
【図２】本発明の第２の実施の形態を示す磁気インピーダンス効果素子の断面図、
【図３】本発明の第３の実施の形態を示す磁気インピーダンス効果素子の断面図、
【図４】本発明の第４の実施の形態を示す磁気インピーダンス効果素子の断面図、
【図５】本発明の第５の実施の形態を示す磁気インピーダンス効果素子の断面図、
【図６】本発明の第６の実施の形態を示す磁気インピーダンス効果素子の断面図、
【図７】参考例の形態を示す磁気インピーダンス効果素子の斜視図、
【図８】図７の形態を示す磁気インピーダンス効果素子の断面図、
【図９】磁気インピーダンス効果素子の感磁部のアスペクト比と、磁界検出感度の関係を示すグラフ、
【図１０】磁気インピーダンス効果素子の感磁部のアスペクト比と、感磁部の両端からの出力電圧Ｅｍｉを最大とする外部磁界の大きさの絶対値Ｈｐとの関係を示すグラフ、
【図１１】本実施の形態の磁気インピーダンス効果素子の磁気インピーダンス効果特性を示す概念図、
【図１２】磁気インピーダンス効果素子の感磁部の磁区構造を示す概念平面図、
【図１３】磁気インピーダンス効果素子の感磁部の磁区構造を示す概念平面図、
【図１４】磁気インピーダンス効果素子の感磁部の磁区構造を示す概念平面図、
【図１５】本発明の磁気インピーダンス効果素子の実施の形態として、バイアス磁界を与える硬磁性体層が設けられた磁気インピーダンス効果素子を示す断面図、
【図１６】本発明の磁気インピーダンス効果素子の実施の形態として、バイアス磁界を与える硬磁性体層が設けられた磁気インピーダンス効果素子を示す断面図、
【図１７】本発明の磁気インピーダンス効果素子の実施の形態として、バイアス磁界を与える反強磁性層が設けられた磁気インピーダンス効果素子を示す断面図、
【図１８】アルミナチタンカーバイドなどの非磁性材料からなる基板上に、感磁部となる軟磁性薄膜と導電性薄膜を成膜した状態を示す斜視図、
【図１９】図１８の多層膜をフォトリソグラフィーおよびエッチングによって、パターン形成して感磁部を形成した状態を示す斜視図、
【図２０】本発明の磁気インピーダンス効果素子の製造方法を実施するために用いることができるＲＦマグネトロンスパッタ装置の断面図、
【図２１】軟磁性薄帯を形成するための液体急冷装置を示す斜視図、
【図２２】本発明の磁気インピーダンス効果素子の感磁部をカー効果偏光顕微鏡によって観察し、写真撮影したものの摸式図、
【図２３】本発明の磁気インピーダンス効果素子の感磁部をカー効果偏光顕微鏡によって観察し、写真撮影したものの摸式図、
【図２４】本発明の磁気インピーダンス効果素子の感磁部をカー効果偏光顕微鏡によって観察し、写真撮影したものの摸式図、
【図２５】本発明の磁気インピーダンス効果素子の感磁部をカー効果偏光顕微鏡によって観察し、写真撮影したものの摸式図、
【図２６】本発明の磁気インピーダンス効果素子の磁気インピーダンス効果特性の実測値を示すグラフ、
【図２７】本発明の磁気インピーダンス効果素子の磁気インピーダンス効果特性の実測値を示すグラフ、
【図２８】磁気インピーダンス効果素子の感磁部のアスペクト比と出力変化量との関係を示すグラフ、
【図２９】従来の磁気インピーダンス効果素子を示す斜視図、
【図３０】磁気インピーダンス効果素子に駆動交流電流を与え、外部磁界を印加する方法を示す回路図、
【符号の説明】
２１ 基板
２２、２４、３２、３４、４２、４４、５２、５４、６２、６４、６６、７２、８１、８５ 軟磁性薄膜
２３、３３、４３、５３、６３、６５、７３、８３ 導電性薄膜
２５、３５、４５、５５、６７、７４、８６ 感磁部
２６、８７ 電極部[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a magneto-impedance effect element that can be used as a magnetic field sensor. In particular, the resistance value of the magneto-impedance effect element can be lowered, power consumption can be reduced, and even when the bias magnetic field is reduced, good magnetic field detection Sensitive magneto-impedance effect elementFor childRelated.
[0002]
[Prior art]
In recent years, with the rapid development of information equipment, measuring equipment, control equipment, etc., there is a demand for a magnetic field sensor that is smaller, more sensitive, and faster in response (high-frequency operation) than the conventional magnetic flux detection type. An element (magnetoimpedance effect element) having (Magneto-Impedance-Effect) has been drawing attention.
[0003]
A magneto-impedance effect element is an element whose basic principle is that an output voltage due to impedance generated by applying a minute alternating current to a magnetic wire formed in a wire shape, ribbon shape or thin film shape is changed by an externally applied magnetic field. is there.
[0004]
The change in impedance of the magnetosensitive part made of soft magnetic material due to the application of an external magnetic field is due to the “skin effect” that causes the alternating current to flow near the surface when an alternating current is applied to the magnetic material. It is known to change.
[0005]
FIG. 29 is a perspective view of a conventional magneto-impedance effect element. The magneto-impedance effect element M shown in FIG. 29 includes a magnetosensitive portion 12 formed by forming a soft magnetic material into a thin film by sputtering or vapor deposition on a substrate 11 made of a nonmagnetic material such as alumina titanium carbide. And electrode portions 13 and 13 formed of a conductive material such as Cu bonded to both ends of the magnetic sensing portion 12. The magnetic sensitive part 12 is patterned in a substantially rectangular shape or linear shape.
29, the element length of the magnetic sensing unit 12 is L, and the element width is W.
[0006]
FIG. 30 is a circuit diagram showing a magnetic field detection circuit configured using a conventional magneto-impedance effect element. In the circuit shown in FIG. 30, when an external magnetic field Hex is applied in the element length direction of the magnetic sensing unit 12 in a state where an alternating current Iac in the MHz band is applied from the power source Eac to the magnetic sensing unit 12, An output voltage Emi due to the material-specific impedance is generated at both ends of the portion 12, and the amplitude of the output voltage Emi changes within a range of several tens of percent corresponding to the strength of the external magnetic field Hex.
[0007]
[Problems to be solved by the invention]
In the conventional magnetic impedance effect element, the magnetic sensing portion 12 is made of a single-layer soft magnetic thin film. The driving AC current flows in the magnetic sensing unit 12.
[0008]
However, the soft magnetic thin film forming the magnetic sensitive portion 12 is often formed of a material having a high specific resistance, and there is a tendency that the direct current loss is increased. In addition, when the soft magnetic thin film is formed of a material having a high specific resistance, the skin thickness when the driving AC current flows is increased, the DC resistance value is decreased, and an external magnetic field is applied to the magnetosensitive portion 12. Impedance changes are smaller. Accordingly, a sufficient amount of change in output voltage cannot be obtained particularly when the drive voltage is low. As a result, a sufficient amount of change in output with respect to the magnetic field cannot be obtained, resulting in a problem that the magnetic field detection sensitivity is reduced.
[0009]
  The present invention is for solving the above-described conventional problems, and the magnetically sensitive part is in contact with a soft magnetic part and a conductor part having a lower specific resistance than the soft magnetic part. Thus, the magneto-impedance effect element can reduce the resistance value of the magneto-impedance effect element, reduce the power consumption, and obtain a sufficient amount of change in the output voltage even when the drive voltage is low.ChildThe purpose is to provide.
[0010]
[Means for Solving the Problems]
  The present invention provides a magneto-impedance effect element in which a magneto-sensitive part having a magneto-impedance effect and an electrode part for applying a driving alternating current to the magneto-sensitive part are provided on a substrate made of a non-magnetic material
  The magnetic sensitive part has a soft magnetic part formed of a soft magnetic material, a conductor part having a lower specific resistance than the soft magnetic part, and the soft magnetic part and the conductor part are: At least partially touchingAnd
  The ratio (aspect ratio) W / L of the element width W and the element length L of the magnetosensitive part is 0.1 or less,
  The soft magnetic part has a single-domain structure or a multi-domain structure, and when the component in the element longitudinal direction of the magnetic moment in each magnetic domain is compared with the component in the element width direction, the component in the element longitudinal direction is more The total area of the large magnetic domains is equal to the total area of the magnetic domains having a larger component in the element width direction.It is characterized by this.
  Alternatively, the present invention provides a magneto-impedance effect element in which a magneto-sensitive part having a magneto-impedance effect and an electrode part for applying a driving AC current to the magneto-sensitive part are provided on a substrate made of a non-magnetic material.
The magnetic sensitive part has a soft magnetic part formed of a soft magnetic material, a conductor part having a lower specific resistance than the soft magnetic part, and the soft magnetic part and the conductor part are: At least partially touching,
The ratio (aspect ratio) W / L of the element width W and the element length L of the magnetosensitive part is 0.1 or less,
  The soft magnetic part has a single-domain structure or a multi-domain structure, and when the component in the element longitudinal direction of the magnetic moment in each magnetic domain is compared with the component in the element width direction, the component in the element longitudinal direction is more The total area of the large magnetic domains is larger than the total area of the large magnetic domains in the component in the element width direction.
[0011]
When the magnetic sensitive part has a structure in which the soft magnetic part and a conductive part having a specific resistance lower than that of the soft magnetic part are in contact with each other, a driving AC current is applied to the magnetic sensitive part. Sometimes, the driving AC current is divided into a current flowing in the soft magnetic body portion and a current flowing in the conductor portion. As a result, the direct-current resistance value of the magnetic sensing portion when the driving alternating current flows can be reduced, and the power consumption of the magneto-impedance effect element can be reduced.
[0012]
In the present invention, since the magnetic sensitive part has a structure in which the soft magnetic part having a high magnetic permeability and the conductive part having a high conductivity are in contact with each other, the driving that flows in the magnetic sensitive part is performed. The skin thickness of the AC current is reduced, the DC resistance value is increased, and a large magneto-impedance effect can be generated, and a sufficient amount of change in output voltage with respect to the magnetic field can be obtained even with a low driving voltage.
[0013]
In the magneto-impedance effect element of the present invention, the magnetically sensitive part may be formed by alternately laminating the soft magnetic part and the conductor part.
[0014]
Further, the uppermost layer and the lowermost layer of the magnetosensitive portion are the soft magnetic body portions, and the uppermost layer and the lowermost soft magnetic body portions are magnetically coupled at least at the end in the element width direction. May be.
[0015]
In particular, when the magnetic sensitive part is one in which the soft magnetic part and the conductive part are alternately laminated, when the thickness of the magnetic sensitive part increases, the film stress increases, The magnetic sensitive part is easily peeled off from the substrate. Therefore, if the element width direction dimension of the upper surface of the magnetic sensing part is shorter than the element width direction dimension of the bottom surface of the magnetic sensing part, film stress can be dispersed and the magnetic sensing part can be prevented from peeling off from the substrate. Further, the magnetic sensitive part can be maintained in a stable shape. For example, the magnetosensitive part can be formed such that the dimension in the element width direction gradually decreases as the distance from the surface of the substrate increases.
[0018]
In the present invention, the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensitive part when an external magnetic field is applied in the longitudinal direction of the element of the magnetic sensitive part to which a driving AC current is applied. The absolute value of the height is preferably 400 (A / m) or less.
[0019]
When the external magnetic field is applied in the longitudinal direction of the element of the magnetosensitive part to which the drive AC current is applied, and the magnitude of the external magnetic field is changed, the rate of change of the output voltage from the magnetosensitive part is: It becomes the largest near the maximum output voltage. Therefore, as the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from the magnetic sensing unit decreases, the rate of change of the output voltage when the magnitude of the external magnetic field is near 0 is obtained. growing. Therefore, the magnitude of the bias magnetic field applied to the magnetic sensitive part can be reduced.
[0020]
In particular, when the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing portion is 400 (A / m) or less, the magneto-impedance effect element is used around the magneto-impedance effect element. It is possible to use the magnetic field generated from the magnetic material made of the magnetic material as a bias magnetic field.
[0021]
Even when the bias magnetic field is applied by a coil wound around the magnetic sensing part, the number of windings of the coil is reduced, and the process for manufacturing the magnetic sensing part can be simplified.
[0022]
Further, it is possible to easily reduce the size required when the magneto-impedance effect element is applied to a magnetic head or a weak magnetic field detector.
[0023]
Furthermore, since the direct current applied to the coil for generating the bias magnetic field can be reduced, power saving of the magneto-impedance effect element is facilitated.
[0024]
In addition, although the said magnetically sensitive part is normally formed in a substantially rectangular shape or linear form, you may form it in a U shape or a zigzag shape. The element longitudinal direction at this time is the extension direction of the longest straight line portion in the magnetosensitive portion, and coincides with the direction perpendicular to the excitation direction of the magnetic field generated by the drive AC current.
[0025]
The absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing portion is preferably 320 (A / m) or less, more preferably from both ends of the magnetic sensing portion. The absolute value of the magnitude of the external magnetic field that maximizes the output voltage is 160 (A / m) or less.
[0027]
The inventor of the present invention, when forming the magnetic sensitive part of the magneto-impedance effect element, decreases the ratio (aspect ratio) W / L of the element width W and the element length L of the magnetic sensitive part. It has been found that the magnetic field detection sensitivity of the magneto-impedance effect element is improved. In particular, it has been found that when the aspect ratio is 0.1 or less, the magnetic field detection sensitivity of the magneto-impedance effect element is significantly improved.
[0028]
Since the magnetic sensitive part is excited by a high frequency alternating current, the skin effect appears strongly. At this time, the element width W, element length L, specific resistance ρ, excitation frequency ω, magnetic permeability μ in the element width direction and impedance magnitude | Z | There is a relationship represented by the following (Equation 1).
[0029]
[Expression 1]

From (Equation 1), when the element width W, the element length L, the specific resistance ρ, and the excitation frequency ω of the magnetosensitive part are constant, the impedance magnitude | Z | It can be seen that this is proportional to the 1/2 power of the magnetic permeability μ. When an external magnetic field is applied in the element longitudinal direction of the magnetosensitive part that is given an alternating current in the element longitudinal direction and excited in the element width direction, the magnetic permeability μ in the element width direction of the magnetosensitive part changes. However, the magnitude | Z | of the magnetosensitive part changes. The external magnetic field applied to the magnetic sensitive part is detected by measuring the change in the impedance magnitude | Z | of the magnetic sensitive part.
[0030]
As the aspect ratio W / L decreases, the rate of change of the impedance magnitude | Z | with respect to the change in the magnetic permeability μ in the element width direction increases. That is, the change in the magnitude of the output voltage drawn from both ends of the magnetic sensing part is increased, and the magnetic field detection sensitivity of the magneto-impedance effect element is improved.
[0031]
Further, the ratio (aspect ratio) W / L of the element width W and the element length L of the magnetosensitive part is preferably 0.05 or less, more preferably, the element width W and the element of the magnetosensitive part. The ratio of length L (aspect ratio) W / L is 0.03 or less.
[0032]
In the case where the magnetic sensing part is formed in a U shape and a folded shape, the total length of the portions of the magnetic sensing part facing the element longitudinal direction is the element length L. The element longitudinal direction at this time is the extension direction of the longest straight line portion in the magnetosensitive portion, and coincides with the direction perpendicular to the excitation direction of the magnetic field generated by the drive AC current.
[0034]
The soft magnetic body portion has a single domain structure or a multi-domain structure, and when the component in the element longitudinal direction of the magnetic moment and the component in the element width direction of each magnetic domain are compared, the component in the element longitudinal direction is more When the total area of the large magnetic domains is equal to the total area of the magnetic domains having a larger component in the element width direction, the direction of the magnetic anisotropy of the soft magnetic body portion as a whole is approximately isotropic. It becomes a state.
[0035]
That is, it becomes difficult to fix the magnetic moment of the soft magnetic body portion in a certain direction, and when the magnetosensitive portion having the soft magnetic body portion is excited by an alternating current, the direction of the magnetic moment of the soft magnetic body portion is changed. It becomes easy to change. That is, the magnetic permeability μ in the element width direction of the soft magnetic body portion increases, and when the external magnetic field is not applied, the magnetic permeability μ in the element width direction of the soft magnetic body portion takes the maximum value. When the permeability μ in the element width direction of the soft magnetic body portion takes the maximum value, the magnitude Z of the impedance of the soft magnetic body portion becomes maximum, and the output voltage from both ends of the magnetic sensing portion also becomes maximum. In other words, the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensitive part is close to zero.
[0037]
In each magnetic domain of the soft magnetic body portion, when the component in the element longitudinal direction of the magnetic moment and the component in the element width direction are compared, the total area of the magnetic domains in which the component in the element longitudinal direction is larger is the element width direction. Even if the component is larger than the total area of the large magnetic domain, the direction of the magnetic anisotropy of the soft magnetic body part constituting the magnetic sensitive part can be made to be close to an isotropic state as a whole. A magnetic field equivalent to a magneto-impedance effect element having a magnetically sensitive portion having a magnetic domain structure in which the total area of magnetic domains having a larger component in the element width direction is equal to the total area of magnetic domains having a larger component in the longitudinal direction of the element Detection sensitivity can be obtained.
[0038]
In addition, when the direction of magnetic anisotropy of the soft magnetic part constituting the magnetic sensing part is close to an isotropic state as a whole, a slight external magnetic field is applied in the longitudinal direction of the element of the magnetic sensing part. As a result, the direction of the magnetic anisotropy of the soft magnetic part can be made substantially isotropic as a whole, and the magnetic permeability μ in the element width direction of the magnetic sensitive part can be maximized. In addition, the output voltage from both ends of the magnetic sensing section can be maximized. That is, the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing part can be reduced.
[0039]
Further, if the magneto-impedance effect element of the present invention has a magnetic body that applies a bias magnetic field in a direction parallel to the longitudinal direction of the element of the magnetosensitive part, the manufacturing process can be simplified and the miniaturization is easy. And power consumption can be reduced.
[0040]
The magnetosensitive part of the magneto-impedance effect element needs to have a ferromagnetic material with soft magnetic properties. Further, the magnetic permeability μ must be high in a high frequency region of 1 MHz to several hundreds of MHz. Further, it is preferable that the magnetostriction constant λ is small so that the external magnetic field (the magnetic field component of the broadcast radio wave) does not apply stress to the soft magnetic material to deteriorate the magnetic characteristics.
[0041]
Since the soft magnetic material is formed as a thin film magnetic material having such properties, the soft magnetic material is preferably formed as a microcrystalline soft magnetic alloy thin film as described below.
[0042]
1. The composition formula is Fe_hM_iO_jA microcrystalline soft magnetic alloy thin film mainly composed of an amorphous structure.
[0043]
However, M is one or more elements selected from Ti, Zr, Hf, V, Nb, Ta, W and rare earth elements, and h, i, and j are at% and 45 ≦ h ≦ 70. Those satisfying the relationship of 5 ≦ i ≦ 30, 10 ≦ j ≦ 40, and h + i + j = 100.
[0044]
Fe is used to obtain a large saturation magnetic flux density Bs, and M is combined with O to increase the specific resistance ρ. When h, i, j is in the above range, a soft magnetic alloy having a large saturation magnetic flux density Bs, specific resistance ρ, and magnetic permeability μ can be obtained. When h, i, j is out of the above range, soft magnetic properties are obtained. Deteriorates.
[0045]
In the above composition, when the element M is one or more elements selected from rare earth elements, h and j are at% and 50 ≦ h ≦ 70 and 10 ≦ j ≦ 30. preferable.
[0046]
2. The composition formula is (Co_1-cT_c)_xM_yX_zO_wA microcrystalline soft magnetic alloy thin film represented by
However, the element T is an element containing one or both of Fe and Ni, and the element M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Si, P, C, W, One or more elements selected from B, Al, Ga, Ge and rare earth elements, and X is one selected from Au, Ag, Cu, Ru, Rh, Os, Ir, Pt, Pd, or It is an element of two or more, and the composition ratio is such that c is 0 ≦ c ≦ 0.7, x, y, z, and w are at%, 3 ≦ y ≦ 30, 0 ≦ z ≦ 20, 7 ≦ w ≦ 40, 20 ≦ y + z + w ≦ 60, and the balance is x.
[0047]
The soft magnetic alloy has a structure in which a microcrystalline phase mainly composed of Co and element T is mixed in an amorphous phase containing a large amount of an oxide of element M, and the microcrystalline phase contains an oxide of element M. It is more preferable that it has.
[0048]
3. The composition formula is T_100-defgX_dM_eZ_fQ_gA microcrystalline soft magnetic alloy thin film mainly composed of one or more kinds of crystal grains of bcc-Fe, bcc-FeCo, and bcc-Co.
[0049]
However, the element T is an element including one or both of Fe and Co, the element X is an element including one or both of Si and Al, and the element M is Ti, Zr, One or more elements selected from Hf, V, Nb, Ta, Mo, and W. The element Z is an element including one or both of C and N, and Q is Cr, It is one or more elements selected from Re, Ru, Rh, Ni, Pd, Pt, and Au, and d, e, f, and g are at%, and 0 ≦ d ≦ 25, 1 ≦ e ≦ 10 , 0.5 ≦ f ≦ 15, 0 ≦ g ≦ 10.
[0050]
If d, e, f, and g are within the above ranges, a soft magnetic alloy thin film having a large magnetic permeability μ, a low coercive force Hc, and a small magnetostriction constant λ can be obtained.
[0051]
4). The composition formula is T_100-pqefgSi_pAl_qM_eZ_fQ_gA microcrystalline soft magnetic alloy thin film mainly composed of one or more kinds of crystal grains of bcc-Fe, bcc-FeCo, and bcc-Co.
[0052]
However, the element T is an element containing one or both of Fe and Co, and the element M is one or more selected from Ti, Zr, Hf, V, Nb, Ta, Mo, and W. The element Z is an element containing one or both of C and N, and Q is one or two selected from Cr, Re, Ru, Rh, Ni, Pd, Pt, and Au. P, q, e, f, and g are at%, 8 ≦ p ≦ 15, 0 ≦ q ≦ 10, 1 ≦ e ≦ 10, 0.5 ≦ f ≦ 15, 0 ≦ g Those satisfying the relation of ≦ 10.
[0053]
If p, q, e, f, and g are within the above ranges, a soft magnetic alloy having a large magnetic permeability μ, a low coercive force Hc, and a small magnetostriction constant λ can be obtained.
[0054]
Further, the magnetically sensitive portion may be formed as having an amorphous soft magnetic alloy thin film or ribbon as shown below.
[0055]
5). The composition formula is (Fe_1-aCo_a)_100-xy(Si_1-bB_b)_xM_yAn amorphous soft magnetic alloy thin film or ribbon indicated by
[0056]
However, M is an element containing one or both of Cr and Ru, and a and b representing the composition ratio are 0.05 ≦ a ≦ 0.1 and 0.2 ≦ b ≦ 0.8. , X and y are at% and satisfy the relationship of 10 ≦ x ≦ 35 and 0 ≦ y ≦ 7.
[0057]
(Fe_1-aCo_a)_100-xy(Si_1-bB_b)_xM_yIn a soft magnetic alloy thin film or ribbon of the type, if a exceeds the range of 0.05 ≦ a ≦ 0.1, the magnetostriction increases, which is not preferable. On the other hand, if b exceeds the range of 0.2 ≦ b ≦ 0.8, it is not preferable because amorphization becomes difficult. Furthermore, when x exceeds the range of 10 ≦ x ≦ 35, it becomes difficult to make the material amorphous. Further, x> 35 is not preferable because the magnetic characteristics deteriorate.
[0058]
6). The composition formula is Co_lTa_mHf_nAn amorphous soft magnetic alloy thin film mainly composed of an amorphous structure.
[0059]
However, l, m, and n are at% and satisfy the relationship of 70 ≦ l ≦ 90, 5 ≦ m ≦ 21, 6.6 ≦ n ≦ 15, and 1 ≦ m / n ≦ 2.5.
[0060]
Co_lTa_mHf_nIn the soft magnetic alloy thin film, the saturation magnetic flux density Bs depends on the Co content, and 70 ≦ l is necessary to obtain a high saturation magnetic flux density Bs. However, it is not preferable that l> 90 because the specific resistance ρ is low.
[0061]
Ta and Hf are elements for obtaining soft magnetic properties. By setting 5 ≦ m ≦ 21 and 6.6 ≦ n ≦ 15, a soft magnetic material having a large saturation magnetic flux density Bs and a large specific resistance ρ is obtained. be able to. Hf is also an element for eliminating the negative magnetostriction constant λ generated in the Co—Ta system. The magnetostriction constant λ depends on the ratio of the content of Ta and the content of Hf, and the magnetostriction constant λ can be satisfactorily eliminated when it is in the range of 1 ≦ m / n ≦ 2.5.
[0062]
7). The composition formula is Co_aZr_bNb_cAn amorphous soft magnetic alloy thin film mainly composed of an amorphous structure represented by
[0063]
However, a, b, and c are at% and satisfy the relationship of 78 ≦ a ≦ 91 and 0.5 ≦ b / c ≦ 0.8.
[0064]
The saturation magnetic flux density Bs depends on the Co concentration. In order to increase Bs, it is necessary to satisfy 78 ≦ a ≦ 91. If a> 91, the corrosion resistance is lowered and an amorphous structure is hardly formed and crystallization starts, which is not preferable. Further, when a <78, the ratio of adjacent Cos decreases, and it becomes difficult to show soft magnetic characteristics, which is not preferable. The magnetic permeability μ also depends on the Co concentration and shows a high value in the range of 78 ≦ a ≦ 91.
[0091]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view showing a magneto-impedance effect element according to a first embodiment of the present invention.
[0092]
The magneto-impedance effect element M of FIG. 1 includes a soft magnetic thin film 22 as a soft magnetic part, a conductive thin film 23 as a conductive part, and a soft magnetic thin film on a substrate 21 made of a nonmagnetic material such as alumina titanium carbide. The magnetic sensing part 25 is formed by sequentially laminating 24, and the electrode parts 26 and 26 are formed on both ends of the magnetic sensing part 25 by a conductive material such as Cu, Ni, Ti, Cr. The magnetic sensitive part 25 is patterned in a substantially rectangular shape or linear shape. Moreover, the magnetic sensitive part 25 may be formed in a U shape or a zigzag shape.
[0093]
In FIG. 1, the electrode portions 26 and 26 are formed at both end portions in the element longitudinal direction of the magnetic sensing portion 25, but the electrode portions 26 and 26 are formed on the vicinity of both end portions on the upper surface of the soft magnetic thin film 24. It may be formed by laminating conductive materials such as.
[0094]
A driving AC current is applied to the magneto-impedance effect element M from the electrode portions 26 and 26 in the longitudinal direction (Y direction) of the element, thereby exciting the magnetosensitive portion 25 in the element width direction (X direction). In this state, when the external magnetic field Hex is applied in the longitudinal direction of the element, the impedance of the magnetic sensing unit 25 changes. A change in impedance of the magnetic sensing unit 25 is taken out as a change in voltage between the electrode units 26 and 26.
[0095]
Here, the longitudinal direction of the element coincides with the direction perpendicular to the excitation direction of the magnetic field generated by the drive AC current.
[0096]
In addition, when the magnetic sensing portion 25 is formed in a U-shape or a bent shape, the extending direction of the longest straight line portion in the magnetic sensing portion becomes the element longitudinal direction, and this direction is generated by the drive AC current. It coincides with the direction perpendicular to the excitation direction of the magnetic field.
[0097]
A protective layer made of an insulating material may be formed on the magnetic sensitive part 25.
The soft magnetic thin films 22 and 24 have, for example, a composition formula of Fe_71.4Al_5.8Si_13.1Hf_3.3C_4.5Ru_1.9This is a microcrystalline soft magnetic alloy thin film having an average crystal grain size of 5 to 30 nm, mainly composed of bcc-Fe crystal grains, and having HfC crystal grains around bcc-Fe.
[0098]
T—X—M—Z—Q system other than this composition (the element T is an element containing one or both of Fe and Co, and the element X is one or both of Si and Al) The element M is one or more elements selected from Ti, Zr, Hf, V, Nb, Ta, Mo, and W, and the element Z is one of C and N Alternatively, Q is an element including both, and Q is a microcrystalline soft magnetic alloy thin film of one or more elements selected from Cr, Re, Ru, Rh, Ni, Pd, Pt, and Au), Co-T —M—X—O system (the element T is an element containing one or both of Fe and Ni, and the element M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Si, One selected from P, C, W, B, Al, Ga, Ge and rare earth elements or X is a composition of one or more elements selected from Au, Ag, Cu, Ru, Rh, Os, Ir, Pt, Pd), bcc-Fe, bcc A microcrystal consisting of a crystal phase of 10-30 nm in average grain size composed of FeCo, bcc-Co, etc. and an amorphous phase containing an oxide of M, wherein the amorphous phase accounts for 50% or more of the entire structure Soft magnetic alloy thin film, Fe-MO system (M is one or more elements selected from Ti, Zr, Hf, V, Nb, Ta, W and rare earth elements), Microcrystalline soft magnetism composed of a crystal phase mainly composed of bcc-Fe and having an average crystal grain size of 10 to 30 nm and an amorphous phase containing M oxide, and the amorphous phase accounts for 50% or more of the entire structure. Soft alloy thin films 22 and 24 may be formed as alloy thin films.
[0099]
Alternatively, an Fe-Co-Si-BM type amorphous soft magnetic alloy thin film of M (M is an element including one or both of Cr and Ru), or an Co-Ta-Hf type amorphous The soft magnetic thin films 22 and 24 may be formed as a soft magnetic alloy thin film or a Co—Zr—Nb amorphous soft magnetic alloy thin film.
[0100]
The conductive thin film 23 is formed of a conductive material such as Cu, Ni, Ti, or Cr. The material used to form the conductive thin film 23 may be any material as long as it has a lower specific resistance than the soft magnetic thin films 22 and 24. For example, it may be a ferromagnetic material containing Fe or Co or an antiferromagnetic material such as NiO or CoO. However, the specific resistance of the material used to form the conductive thin film 23 is preferably a material having a specific resistance of 1/10 or less of the specific resistance of the material used to form the soft magnetic thin films 22 and 24.
[0101]
In the present embodiment, the magnetic sensitive part 25 is formed as soft magnetic thin films 22 and 24 and conductive thin films 23 alternately stacked. When the soft magnetic thin films 22 and 24 made of a soft magnetic material and a conductive thin film 23 formed of a material having a specific resistance lower than that of the soft magnetic material are in contact with each other, the magnetic sensing unit 25 is driven. When an alternating current is applied, the driving alternating current is divided into a current flowing in the soft magnetic thin films 22 and 24 and a current flowing in the conductive thin film 23. As a result, the DC resistance value of the magnetic sensing unit 25 when the driving AC current flows can be reduced, and the power consumption of the magneto-impedance effect element can be reduced.
[0102]
In addition, since the magnetic sensitive part 25 has a structure in which the soft magnetic thin films 22 and 24 having a high magnetic permeability and the conductive thin film 23 having a high electric conductivity are in contact with each other, the drive AC current flowing in the magnetic sensitive part can be reduced. The skin thickness is reduced and a large magneto-impedance effect can be generated. Therefore, a sufficient amount of change in the output voltage with respect to the magnetic field can be obtained even with a low driving voltage.
[0103]
FIG. 2 is a cross-sectional view of the magnetic sensing part of the magneto-impedance effect element according to the second embodiment of the present invention.
[0104]
The magneto-impedance effect element shown in FIG. 2 has a soft magnetic thin film 32 as a soft magnetic part, a conductive thin film 33 as a conductive part, and a soft magnetic thin film 34 on a substrate 21 made of a nonmagnetic material such as alumina titanium carbide. Has a magnetic sensing portion 35 formed by sequentially laminating. In the present embodiment, the uppermost soft magnetic thin film 34 and the lowermost soft magnetic thin film 32 of the magnetic sensing portion 35 are magnetically coupled at the end in the element width direction, and When a driving AC current is passed, a closed circular magnetic field can be generated in the soft magnetic thin film 34 and the soft magnetic thin film 32.
[0105]
FIG. 3 is a cross-sectional view of the magnetic sensing part of the magneto-impedance effect element according to the third embodiment of the present invention.
[0106]
The magneto-impedance effect element shown in FIG. 3 includes a soft magnetic thin film 42 as a soft magnetic part, a conductive thin film 43 as a conductive part, and a soft magnetic thin film 44 on a substrate 21 made of a nonmagnetic material such as alumina titanium carbide. Has a magnetically sensitive portion 45 formed by sequentially laminating. In the present embodiment, the element width direction (Y direction) dimension is gradually shortened as the magnetically sensitive portion 45 moves away from the surface 21 a of the substrate 21. Therefore, the film stress can be dispersed, the magnetic sensitive part 45 can be prevented from peeling off from the substrate, and the magnetic sensitive part 45 can be maintained in a stable shape.
[0107]
The cross-sectional shape of the magnetic sensing part 45 is not limited to the shape shown in FIG. 3, and the element width direction dimension of the upper surface 45 a of the magnetic sensing part 45 is made shorter than the element width direction dimension of the bottom surface 45 b of the magnetic sensing part 45. It only has to be. For example, both end portions in the element width direction of the magnetic sensitive portion 45 may be formed in a step shape.
[0108]
FIG. 4 is a cross-sectional view of the magnetic sensing part of the magneto-impedance effect element according to the fourth embodiment of the present invention.
[0109]
The magneto-impedance effect element of the present invention does not necessarily have to be formed by sequentially laminating a soft magnetic thin film and a conductive thin film in the vertical direction.
[0110]
For example, as shown in FIG. 4, a soft magnetic thin film 52, a conductive thin film 53, and a soft magnetic thin film 54 are formed on the same surface of the surface 21a of the substrate 21 made of a nonmagnetic material such as alumina titanium carbide. A magneto-impedance effect element having a magnetosensitive part 55 having a structure in which the soft magnetic thin film 52 and the conductive thin film 53 are in contact with each other and the conductive thin film 53 and the soft magnetic thin film 54 are in contact with each other may be used.
[0111]
In the magneto-impedance effect element having the magnetic sensing portion 55 of FIG. 4, when a driving AC current is applied to the magnetic sensing portion 55, the driving AC current flows through the soft magnetic thin films 52 and 54 and the conductive thin film 53. It is divided into current flowing through it. As a result, the DC resistance value of the magnetic sensing unit 55 when the driving AC current flows can be reduced, and the power consumption of the magneto-impedance effect element can be reduced.
[0112]
Further, since the magnetic sensitive part 55 has a structure in which the soft magnetic thin films 52 and 54 having a high magnetic permeability and the conductive thin film 53 having a high electric conductivity are in contact with each other, the drive AC current flowing in the magnetic sensitive part is reduced. The skin thickness is reduced and a large magneto-impedance effect can be generated. Therefore, a sufficient amount of change in the output voltage with respect to the magnetic field can be obtained even with a low driving voltage.
[0113]
FIG. 5 is a cross-sectional view of the magnetic sensing part of the magneto-impedance effect element according to the fifth embodiment of the present invention.
[0114]
In the present invention, any number of layers of the soft magnetic thin film and the conductive thin film of the magnetic sensitive portion may be laminated.
[0115]
For example, as shown in FIG. 5, on a substrate 21 made of a nonmagnetic material such as alumina titanium carbide, a soft magnetic thin film 62 that is a soft magnetic part, a conductive thin film 63 that is a conductive part, a soft magnetic thin film 64, and a conductive part. A magneto-impedance effect element having a magnetosensitive portion 67 formed by sequentially laminating a conductive thin film 65 and a soft magnetic thin film 66 may be used.
[0116]
The uppermost soft magnetic thin film 66 and the lowermost soft magnetic thin film 62 may be magnetically coupled at the end in the element width direction. Further, the element width direction (Y direction) dimension may be gradually shortened as the magnetic sensitive portion 67 moves away from the surface 21a of the substrate 21.
[0117]
FIG. 6 is a cross-sectional view of the magnetic sensing part of the magneto-impedance effect element according to the sixth embodiment of the present invention.
[0118]
In the present invention, the conductive thin film of the magnetic sensitive part does not necessarily have to be sandwiched between a plurality of soft magnetic thin films.
[0119]
For example, as shown in FIG. 6, a magnetic impedance having a magnetosensitive portion 74 formed by sequentially laminating only a soft magnetic thin film 72 and a conductive thin film 73 on a substrate 21 made of a nonmagnetic material such as alumina titanium carbide. An effect element may be sufficient.
[0120]
In addition, the electrode part for giving a drive alternating current to the element longitudinal direction (Y direction) of a magnetosensitive part in the both ends of the magnetosensitive part 35, 45, 55, 67, and 74 is Cu, Ni, Ti, Cr Formed of a conductive material. The magnetic sensitive portions 35, 45, 55, 67, and 74 are patterned in a substantially rectangular shape or linear shape. Alternatively, the magnetic sensitive portions 35, 45, 55, 67, and 74 may be formed in a U shape or a zigzag shape.
[0121]
A drive alternating current is applied in the element longitudinal direction (Y direction) of the magnetic sensing portions 35, 45, 55, 67, and 74, and excitation is performed in the element width direction (X direction). In this state, when the external magnetic field Hex is applied in the longitudinal direction of the element, the impedances of the magnetic sensitive portions 35, 45, 55, 67, and 74 change. The impedance change of the magnetic sensitive parts 35, 45, 55, 67 and 74 is taken out as a change in voltage between the electrode parts.
[0122]
Note that a protective layer made of an insulating material may be formed on the magnetic sensitive portions 35, 45, 55, 67 and 74.
[0123]
  FIG.Reference exampleFIG. 8 is a cross-sectional view of the magneto-impedance effect element shown in FIG. 7 taken along line 8-8.
[0124]
7 and 8, on the substrate 21 made of a nonmagnetic material such as alumina titanium carbide, the soft magnetic thin film 81, the insulating layer 82 made of an insulating material, the conductive thin film 83, the insulating layer 84, A soft magnetic thin film 85 is sequentially laminated to form a magnetic sensitive portion 86.
[0125]
The soft magnetic thin film 81 and the conductive thin film 83 are electrically insulated by the insulating layer 82. In addition, the conductive thin film 83 and the soft magnetic thin film 85 are electrically insulated by the insulating layer 84.
[0126]
Electrode portions 87 and 87 for applying a driving AC current in the element longitudinal direction (Y direction) of the conductive thin film 83 are formed by conductive materials such as Cu, Ni, Ti, and Cr at both ends of the magnetosensitive portion 86. It is formed. The electrode portions 87 and 87 are connected only to the conductive thin film 83. The soft magnetic thin film 81 and the electrode portions 87 and 87 are electrically insulated by the insulating layer 82. Further, the soft magnetic thin film 85 and the electrode portions 87 and 87 are electrically insulated by the insulating layer 84. Accordingly, the driving AC current is passed only through the conductive thin film 83.
[0127]
A driving AC current is applied in the element longitudinal direction (Y direction) of the conductive thin film 83 to excite it in the element width direction (X direction). In this state, when the external magnetic field Hex is applied in the longitudinal direction of the element, the impedance of the magnetic sensing part 86 changes. The impedance change of the magnetic sensing part 86 is taken out as a change in voltage between the electrode parts.
[0128]
When the driving AC current is applied only to the conductive thin film 83 and not to the soft magnetic thin films 81 and 85, an exciting magnetic field due to the driving AC current can be generated efficiently, and a more prominent magnetic impedance effect can be obtained. It becomes possible.
[0129]
The magnetic sensitive part 86 is patterned in a substantially rectangular shape or linear shape. Alternatively, the magnetic sensing part 86 may be formed in a U shape or a zigzag shape.
[0130]
FIG. 9 is a graph showing the relationship between the aspect ratio of the magnetic sensing part of the magneto-impedance effect element and the magnetic field detection sensitivity. In the graph of FIG. 9, the element length L of the magnetic sensing part is fixed to 4 mm or 6 mm, and the aspect ratio W / L of the magnetic sensing part is changed by changing the element width W. As is apparent from FIG. 9, it can be seen that when the aspect ratio W / L of the magnetosensitive portion is 0.1 or less, the magnetic field detection sensitivity of the magneto-impedance effect element is improved. In particular, when the element length L of the magnetic sensing part is 6 mm, the magnetic field detection sensitivity of the magneto-impedance effect element can be drastically improved when the aspect ratio W / L of the magnetic sensing part is about 0.08 or less. Recognize.
[0131]
When the magnetic sensing part is formed in a U-shape and a zigzag shape, the total length of the portions of the magnetic sensing part facing the element longitudinal direction is the element length L.
[0132]
In the present embodiment, the magnetic sensing unit 25 is formed with, for example, an element width W of 0.10 mm and an element length L of 6 mm. At this time, the aspect ratio of the magnetic sensing portion 25 of the magneto-impedance effect element M is W / L = 0.177.
[0133]
When the element length of the magneto-impedance effect element M shown in FIG. 1 is 6 mm and the aspect ratio is 0.017, it is about 2.5 (mV · m / A) (about 200 (mV / Oe)).
[0134]
FIG. 10 shows the relationship between the aspect ratio (W / L) of the magnetosensitive part of the magneto-impedance effect element and the absolute value (Hp) of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetosensitive part. It is a graph to show.
[0135]
From the graph of FIG. 10, when the aspect ratio (W / L) of the magnetosensitive part of the magneto-impedance effect element is reduced, the absolute value (Hp) of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetosensitive part. It can be seen that also becomes smaller. In the graph of FIG. 3, the element length of the magnetic sensing part is fixed to 4 mm or 6 mm, and the aspect ratio of the magnetic sensing part is changed by changing the element width.
[0136]
For example, when the element length of the magnetic sensing portion is 6 mm and the aspect ratio (W / L) is about 0.1 or less, the absolute magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing portion The value (Hp) is 320 (A / m) (4 (Oe)) or less. In addition, even when the element length of the magnetic sensing portion is 4 mm, when the aspect ratio (W / L) is about 0.1 or less, the absolute value (Hp) of the magnitude of the external magnetic field that maximizes the output voltage is 320 (A / m) (4 (Oe)) or less.
[0137]
When the element length of the magnetic sensing portion is 6 mm and the aspect ratio (W / L) is about 0.05 or less, the absolute value (Hp) of the magnitude of the external magnetic field that maximizes the output voltage is 160 ( A / m) (2 (Oe)) or less.
[0138]
Since the magnetosensitive part 25 of the magneto-impedance effect element M of the present embodiment shown in FIG. 1 has an element length of 6 mm and an aspect ratio of 0.017, the output voltage is maximized from the graph of FIG. It can be seen that the absolute value of the magnitude of the external magnetic field is in the range of approximately 0 to 24 (A / m) (0.3 (Oe)).
[0139]
FIG. 11 is a conceptual diagram for explaining the magneto-impedance effect characteristics of the magneto-impedance effect element of the present embodiment.
[0140]
An external magnetic field Hex is applied in the element longitudinal direction of the magneto-impedance effect element M in a state where a drive AC current is applied from the electrode parts 26 and 26 of the magneto-impedance effect element M in FIG. When the output voltage Emi is measured while changing the magnitude of the applied external magnetic field Hex, a graph as shown in FIG. 11 is obtained.
[0141]
The conceptual diagram showing the magneto-impedance effect characteristic of FIG. 11 shows that the magnitude of the external magnetic field Hex is Hp.₊Or Hp_-A bimodal shape having a vertex indicating a value indicating the value of the output voltage Emi at the time of. Hp₊And Hp_-The absolute values of are almost equal and approximately 0 to 24 (A / m) (0.3 (Oe)).
[0142]
In FIG. 11, the magnitude of the external magnetic field Hex is Hp.₊Or Hp_-As the value approaches, the rate of change of the output voltage Emi increases. That is, the detection sensitivity of the external magnetic field Hex is such that the magnitude of the external magnetic field Hex is Hp.₊Or Hp_-Good when near.
[0143]
Hp₊Or Hp_-In order to improve the detection sensitivity of the external magnetic field Hex in the vicinity of the external magnetic field Hex = 0, when the absolute value of the magnitude of is approximately 0 to 24 (A / m) (0.3 (Oe)) The magnitude of the bias magnetic field applied in the element longitudinal direction of the portion 25 is, for example, H_B= 0 to 80 (A / m) (1 (Oe)) is sufficient. In the examples described later, a graph of magneto-impedance effect characteristics based on actual measurement values of the magneto-impedance effect element will be described.
[0144]
Hp₊Or Hp_-Is not more than 400 (A / m) (5 (Oe)), preferably not more than 320 (A / m) (4 (Oe)), more preferably not more than 160 (A / m) (2Oe) If so, the magnitude of the bias magnetic field applied in the longitudinal direction of the element of the magnetosensitive portion 25 is 400 (A / m) (5 (Oe)) or less, preferably 320 (A / m) (4 (Oe)) or less. , More preferably 160 (A / m) (2Oe) or less.
[0145]
If the required bias magnetic field applied in the longitudinal direction of the element of the magnetic sensing part 25 can be 400 (A / m) or less, a hard magnetic material formed around the magnetic sensing part 25, or A magnetic field generated from a magnetic film made of a hard magnetic material or an antiferromagnetic material formed so as to overlap the magnetic sensing portion 25 can be used as a bias magnetic field.
[0146]
Further, the magnitude of the bias magnetic field applied in the longitudinal direction of the element of the magnetic sensing portion 25 is 400 (A / m) (5 (Oe)) or less, preferably 320 (A / m) (4 (Oe)) or less. Preferably, if it can be set to 160 (A / m) (2 Oe) or less, in order to apply a bias magnetic field to the magnetic sensing portion 25, the number of turns of the coil wound around the magnetic sensing portion 25 is reduced, and the magneto-impedance effect element The process at the time of manufacturing can be simplified. In addition, it is easy to reduce the size required when the magneto-impedance effect element M is applied to a magnetic head or a weak magnetic field detector. Further, since the direct current applied to the coil for generating the bias magnetic field can be reduced, the power saving of the magneto-impedance effect element M is facilitated.
[0147]
If the ratio (aspect ratio) W / L of the element width W and the element length L of the magnetosensitive element of the magnetoimpedance effect element is reduced, the effect of improving the magnetic field detection sensitivity of the magnetoimpedance effect element can be obtained. The reason is as follows.
[0148]
Since the magnetic sensitive part is excited by a high frequency alternating current, the skin effect appears strongly. At this time, the element width W, element length L, specific resistance ρ, excitation frequency ω, magnetic permeability μ in the element width direction and impedance magnitude | Z | There is a relationship represented by the following (Equation 2).
[0149]
[Expression 2]

From (Equation 2), when the element width W, element length L, specific resistance ρ, and excitation frequency ω of the magnetosensitive part are constant, the magnitude | Z | of the magnetosensitive part is the element width direction. It can be seen that this is proportional to the 1/2 power of the magnetic permeability μ.
[0150]
When an external magnetic field is applied in the element longitudinal direction of the magnetosensitive part that is given an alternating current in the element longitudinal direction and excited in the element width direction, the magnetic permeability μ in the element width direction of the magnetosensitive part changes. However, the magnitude | Z | of the magnetosensitive part changes. The external magnetic field applied to the magnetic sensitive part is detected by measuring the change in the magnitude | Z | of the magnetic sensitive part.
[0151]
As the aspect ratio W / L decreases, the rate of change of the impedance magnitude | Z | with respect to the change in the magnetic permeability μ in the element width direction increases. That is, the change in the magnitude of the output voltage drawn from both ends of the magnetic sensing part is increased, and the magnetic field detection sensitivity of the magneto-impedance effect element is improved.
[0152]
FIG. 12 is a conceptual plan view showing an example of the magnetic domain structure of the soft magnetic thin film constituting the magnetic sensing part of the magneto-impedance effect element.
[0153]
FIG. 12 shows the magnetic domain structure of the soft magnetic thin film 22 among the soft magnetic thin films 22 and 24 constituting the magnetic sensing portion 25 of the magneto-impedance effect element M shown in FIG. The magnetic domain structure is almost the same as the magnetic domain structure of the soft magnetic thin film 22. The soft magnetic thin film 22 has a magnetic anisotropy in the element width direction by being formed in a static magnetic field or by using a soft magnetic material having strong anisotropy. Therefore, the magnetic domain 22a in which the magnetic moment is oriented in the element width direction is formed. Note that the element width of the soft magnetic thin film 22 in FIG.
[0154]
On the other hand, the magnetic domain 22b in which the magnetic moment is oriented in the longitudinal direction of the element of the soft magnetic thin film 22 is formed by the shape magnetic anisotropy.
[0155]
When the aspect ratio of the soft magnetic thin film 22 is large, the total area of the magnetic domains 22b in which the magnetic moment is aligned in the element longitudinal direction is significantly narrower than the total area of the magnetic domains 22a in which the magnetic moment is aligned in the element width direction. Become.
[0156]
FIG. 13 is a conceptual plan view showing another magnetic domain structure of the soft magnetic thin film 22 of the magneto-impedance effect element M. FIG.
[0157]
For example, the aspect ratio of the soft magnetic thin film 22 is made smaller than 0.1 by making the element width of the soft magnetic thin film 22 smaller than W1.
[0158]
In FIG. 13, the magnetic domain 22b is a magnetic domain in which the component in the element longitudinal direction is larger when the component in the element longitudinal direction of the magnetic moment is compared with the component in the element width direction. This component is a larger magnetic domain. In FIG. 13, the total area of the magnetic domains 22b is almost the same as the total area of the magnetic domains 22b of FIG. 12, and the total area of the magnetic domains 22a is smaller than the total area of the magnetic domains 22a of FIG. The area values are equal. As a result, the direction of magnetic anisotropy of the soft magnetic thin film 22 as a whole becomes substantially isotropic.
[0159]
When the total area of the magnetic domains 22b, which are magnetic domains having a larger component in the element longitudinal direction, and the total area of the magnetic domains 22a, which are magnetic domains having a larger component in the element width direction, antagonize, that is, the element width direction and the element longitudinal direction. When the magnetic anisotropy energy is balanced, the soft magnetic thin film 22 becomes almost isotropic as a whole in the direction of magnetic anisotropy. That is, the magnetic moment of the soft magnetic thin film 22 is difficult to be fixed in a certain direction, and the direction of the magnetic moment is easily changed when excited by an alternating current. That is, the magnetic permeability μ in the element width direction of the soft magnetic thin film 22 is increased.
[0160]
When the magnetic permeability μ in the element width direction of the soft magnetic thin film 22 takes the maximum value, the magnitude Z of the impedance of the soft magnetic thin film 22 is maximized, and the output voltage from both ends of the soft magnetic thin film 22 is also maximized.
[0161]
In FIG. 13, when an external magnetic field is not applied, the soft magnetic thin film 22 is in a state in which the direction of magnetic anisotropy is close to an isotropic state as a whole.
[0162]
Therefore, the direction of the magnetic anisotropy of the soft magnetic thin film 22 as a whole is almost isotropic without applying the external magnetic field Hex or slightly applying the external magnetic field Hex in the longitudinal direction of the element of the soft magnetic thin film 22. Thus, the magnetic permeability μ in the element width direction of the soft magnetic thin film 22 can be maximized, and the output voltage Emi from both ends of the soft magnetic thin film 22 can be maximized.
[0163]
That is, when the external magnetic field Hex is applied to the soft magnetic thin film 22 to which the drive AC current is applied, the absolute value Hp of the magnitude of the external magnetic field Hex that maximizes the output voltage Emi from the soft magnetic thin film 22 is decreased. be able to.
[0164]
The soft magnetic thin film 22 may have a single magnetic domain structure, and the component in the element longitudinal direction and the component in the element width direction of the magnetic moment may be balanced in each magnetic domain.
[0165]
Further, in the magneto-impedance effect element of the present invention, as shown in FIG. 14, the total area of the magnetic domain 22b, which is a magnetic domain having a larger component in the element longitudinal direction, is a magnetic domain having a larger component in the element width direction. Even when it is larger than the total area of a certain magnetic domain 22a, the direction of the magnetic anisotropy of the soft magnetic thin film 22 can be made close to an isotropic state as a whole, and the total area of the magnetic domains 22b and the total of the magnetic domains 22a can be made. Magnetic field detection sensitivity equivalent to that of the magneto-impedance effect element having the soft magnetic thin film 22 having a magnetic domain structure in which the area is antagonized can be obtained.
[0166]
In the magneto-impedance effect element of the present embodiment, the magnetic field detection sensitivity can be at least 0.3 (mV · m / A) (25 mV / Oe), which is a practical range for a magnetic field sensor.
[0167]
In addition, the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing unit 25 can be reduced.
[0168]
15 to 17 are longitudinal sectional views of a magneto-impedance effect element that can apply a bias magnetic field by a thin film magnetic material as an embodiment of the magneto-impedance effect element of the present invention.
[0169]
The magneto-impedance effect element shown in FIG. 15 has a magnetic sensing portion 94 made of a soft magnetic thin film 91, a conductive thin film 92, and a soft magnetic thin film 93 formed on a substrate 21, and electrodes are provided at both ends of the magnetic sensing portion 94 in the longitudinal direction of the element. 95 and 95 are further provided, and hard magnetic layers 96 and 96 which are magnetic thin films that are in contact with both ends of the magnetic sensing portion 94 are provided. The hard magnetic layers 96 and 96 are made of a hard magnetic material such as CoPt.
[0170]
The magnitude of the bias magnetic field that can be applied by the hard magnetic layers 96, 96 is about 400 A / m at the maximum. In the magneto-impedance effect element according to the present embodiment, the bias magnetic field is applied in the element longitudinal direction of the magnetosensitive part 94. Since the necessary bias magnetic field can be made 400 (A / m) or less, a sufficient bias magnetic field is applied to the magnetic sensing portion 94 by the hard magnetic layers 96 and 96 as shown in FIG. Can do. That is, since it is not necessary to use a winding coil through which a direct current flows in order to apply a bias magnetic field, the magneto-impedance effect element can be reduced in size and power consumption.
[0171]
Further, as shown in FIG. 16, hard magnetic layers 96 and 96 are formed at both ends in the element longitudinal direction of the magnetic sensing portion 94, and electrodes 95 and 95 are formed on the hard magnetic layers 96 and 96. May be.
[0172]
Alternatively, as shown in FIG. 17, antiferromagnetic layers 97 and 97 are laminated on the upper and lower layers of the magnetic sensing part 94, and the soft magnetic thin films 91 and 93 and the antiferromagnetic layers 97 and 97 of the magnetic sensing part 94 are stacked. It is also possible to give a necessary bias magnetic field to the magnetic sensing part 94 by the exchange anisotropic magnetic field generated at the interface of the magnetic field.
[0173]
18 and 19 are perspective views for explaining a method of manufacturing the magneto-impedance effect element shown in FIG.
[0174]
In FIG. 18, a soft magnetic thin film 22, a conductive thin film 23 and a soft magnetic thin film 24 are sequentially sputtered, vapor deposited or plated on a substrate 21 made of a nonmagnetic material such as alumina titanium carbide, glass, ceramic, crystallized glass or the like. It is a perspective view which shows the state which formed into a film by the method etc. and was laminated | stacked.
[0175]
The soft magnetic thin films 22 and 24 have, for example, a composition formula of Fe_71.4Al_5.8Si_13.1Hf_3.3C_4.5Ru_1.9This is a microcrystalline soft magnetic alloy thin film mainly composed of bcc-Fe crystal grains.
[0176]
T—X—M—Z—Q system other than this composition (the element T is an element containing one or both of Fe and Co, and the element X is one or both of Si and Al) The element M is one or more elements selected from Ti, Zr, Hf, V, Nb, Ta, Mo, and W, and the element Z is one of C and N Alternatively, Q is an element including both, and Q is a microcrystalline soft magnetic alloy thin film of one or more elements selected from Cr, Re, Ru, Rh, Ni, Pd, Pt, and Au), Co-T —M—X—O system (the element T is an element containing one or both of Fe and Ni, and the element M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Si, One selected from P, C, W, B, Al, Ga, Ge and rare earth elements or X is a composition of one or more elements selected from Au, Ag, Cu, Ru, Rh, Os, Ir, Pt, and Pd), and bcc-Fe, bcc A microcrystal composed of a crystal phase composed of FeCo, bcc-Co or the like and having an average crystal grain size of 10 to 30 nm and an amorphous phase containing M oxide, and the amorphous phase occupies 50% or more of the entire structure Soft magnetic alloy thin film, Fe-MO system (M is one or more elements selected from Ti, Zr, Hf, V, Nb, Ta, W and rare earth elements), Microcrystalline soft magnetism composed of a crystal phase mainly composed of bcc-Fe and having an average crystal grain size of 10 to 30 nm and an amorphous phase containing M oxide, and the amorphous phase accounts for 50% or more of the entire structure. As the alloy thin film, soft magnetic thin films 22 and 24 may be formed.
[0177]
Alternatively, the soft magnetic thin films 22 and 24 may be formed as a Co—Ta—Hf amorphous soft magnetic alloy thin film or a Co—Zr—Nb amorphous soft magnetic alloy thin film.
[0178]
The conductive thin film 23 is formed of a conductive material such as Cu, Ni, Ti, or Cr. The material used to form the conductive thin film 23 may be any material as long as it has a lower specific resistance than the soft magnetic thin films 22 and 24. For example, it may be a ferromagnetic material containing Fe or Co or an antiferromagnetic material such as NiO or CoO. However, the specific resistance of the material used to form the conductive thin film 23 is preferably a material having a specific resistance of 1/10 or less of the specific resistance of the material used to form the soft magnetic thin films 22 and 24.
[0179]
In this embodiment, the soft magnetic thin film 22, the conductive thin film 23, and the soft magnetic thin film 24 are formed using an RF magnetron sputtering apparatus. The conditions during film formation are in the following range.
[0180]
High frequency power: 200 to 400 (W)
Ar gas pressure: 50 (sccm)
Deposition pressure: 3-7 (mTorr)
Static magnetic field strength during film formation: 790 or more (A / m)
Deposition rate: 10-33.5 (nm / min)
The standard conditions are: high frequency power is 400 (W), Ar gas pressure is 50 (sccm), film forming pressure is 7 (mTorr), film forming static magnetic field strength is 4740 (A / m), film forming speed. Is 33.5 (nm / min). The substrate was cooled by indirect cooling.
[0181]
Next, the magnetic sensitive portion 25 is formed by patterning the soft magnetic thin film 22, the conductive thin film 23, and the soft magnetic thin film 24 by photolithography and etching as shown in FIG. At this time, the magnetosensitive part 25 is patterned in a substantially rectangular shape so that the ratio W / L (aspect ratio) of the element width W and the element length L is 0.1 or less.
[0182]
The magnetic sensitive part 25 is formed, for example, with an element width W of 100 μm and an element length L of 6 mm. Therefore, the aspect ratio of the magnetic sensing portion 25 of the magneto-impedance effect element M of the present embodiment is W / L = 0.177.
[0183]
In addition, although the magnetic sensitive part 25 is formed in the one surface on the board | substrate 21, only one part is shown in FIG.
[0184]
In the present embodiment, after patterning the magnetic sensing part 25, a static magnetic field H2 is applied in the element width direction of the magnetic sensing part 25 and subjected to heat treatment.
[0185]
When the soft magnetic thin film 22 and the soft magnetic thin film 24 are formed, the static magnetic field H1 may be applied in the direction of the arrow in FIG. 18 which is the element width direction when the magnetoimpedance effect element in FIG. 1 is completed. When film formation is performed in a magnetic field as described above, the heat treatment process in a static magnetic field after film formation can be omitted. Alternatively, after film formation in a magnetic field, heat treatment in a rotating magnetic field or no magnetic field may be performed instead of heat treatment in a static magnetic field.
[0186]
The conditions for the heat treatment in a static magnetic field, or the heat treatment in a rotating magnetic field or no magnetic field are in the following ranges.
[0187]
Static magnetic field strength: 0 to 79000 (A / m)
Heat treatment temperature: 540-675 (° C)
Heat treatment time: 20-30 (min)
Temperature increase rate: 10-14 (° C / min)
Standard conditions are a static magnetic field strength of 79000 (A / m), a heat treatment temperature of 575 (° C.), a heat treatment time of 30 (min), and a temperature increase rate of 13.6 (° C./min).
[0188]
In the present embodiment, after the soft magnetic thin film 22, the conductive thin film 23, and the soft magnetic thin film 24 are sequentially formed as shown in FIG. 18, the magnetic sensitive portion 25 is patterned as shown in FIG. In the static magnetic field, after the soft magnetic thin film 22, the conductive thin film 23, and the soft magnetic thin film 24 are formed, before the magnetic sensitive portion 25 is patterned, that is, in the state of FIG. A heat treatment in a static magnetic field may be performed, and then the magnetosensitive portion 25 may be patterned.
[0189]
Heat treatment in a static magnetic field, a rotating magnetic field, or no magnetic field substantially antagonizes the shape magnetic anisotropy generated in the longitudinal direction of the element of the soft magnetic thin film and the magnetic anisotropy in the element width direction, thereby This is performed to make the direction of the magnetic anisotropy of the magnetic part almost isotropic as a whole.
[0190]
That is, the film formation and heat treatment steps in the magnetic field are performed in order to keep the permeability μ in the element width direction high even when the aspect ratio W / L is reduced. It is not just for giving magnetic anisotropy in the direction.
[0191]
After patterning the magnetic sensitive portion 25 and performing heat treatment in a magnetic field, as shown in FIG. 1, electrode portions 26 made of a conductive material such as Cu, Ni, Ti, Cr are formed on both ends of the magnetic sensitive portion 25, as shown in FIG. 26 is formed by sputtering, photolithography, and etching.
[0192]
After forming the electrode parts 26, 26, the substrate 21 is cut to obtain individual magneto-impedance effect elements M as shown in FIG.
[0193]
When the magneto-impedance effect element as shown in FIG. 2 is manufactured, the soft magnetic thin film 32 and the conductive thin film 33 are patterned on the substrate 21, and then the soft magnetic thin film 34 is formed. The soft magnetic thin film 34 is magnetically connected at both ends in the element width direction.
[0194]
When the magneto-impedance effect element as shown in FIG. 3 is manufactured, the soft magnetic thin film 42, the conductive thin film 43, and the soft magnetic thin film are formed on the substrate 21 made of a nonmagnetic material such as alumina titanium carbide, glass, ceramic, or crystallized glass. 44 are sequentially formed by sputtering, vapor deposition, plating, or the like to form a multilayer film similar to that shown in FIG. 18, and then a photoresist is laminated on the soft magnetic thin film 44. The photoresist is formed in the same shape and size as the magnetic sensitive part 45 to be formed. For example, it is formed in a substantially rectangular shape having a width of 100 μm and a length of 6 mm.
[0195]
Next, the magnetosensitive portion 45 is patterned by performing an etching process on the multilayer film on which the photoresist is laminated using an acidic aqueous solution containing hydrofluoric acid, hydrogen peroxide solution, or the like. With this etching process, the element width direction (X direction) dimension is gradually shortened as the magnetic sensitive part 45 is separated from the surface of the substrate 21, that is, tapered surfaces 45c at both ends in the element width direction as shown in FIG. , 45c can be formed.
[0196]
When manufacturing the magneto-impedance effect element shown in FIGS. 7 and 8, after patterning the soft magnetic thin film 81 on the substrate 21, the insulating layer 82, the conductive thin film 83, and the insulating layer 84 are sequentially stacked. The electrode portions 87 and 87 that are electrically connected only to the conductive thin film 83 may be formed.
[0197]
In FIG. 19, the magnetosensitive part 25 of the magneto-impedance effect element has a structure in which a soft magnetic thin film 22 and a soft magnetic thin film 24 are laminated on top and bottom of a conductive thin film 23. The step of laminating the conductive thin film and the soft magnetic thin film may be repeated.
[0198]
When manufacturing the magneto-impedance effect element shown in FIG. 2 to FIG. 8, after forming the magnetic sensitive portions 35, 45, 55, 67, 74, 86, the magnetic sensitive portions 35, 45, 55, A static magnetic field is applied in the element width direction of 67, 74, 86.
[0199]
When forming the soft magnetic thin film included in the magnetic sensitive portions 35, 45, 55, 67, 74, 86, a static magnetic field may be applied in the direction that is the element width direction of the magnetic sensitive portion. When film formation is performed in a magnetic field as described above, the heat treatment process in a static magnetic field after film formation can be omitted. Alternatively, after film formation in a magnetic field, heat treatment in a rotating magnetic field or no magnetic field may be performed instead of heat treatment in a static magnetic field.
[0200]
Further, the magnetic sensitive portions 25, 35, 45, 55, 67, 74, 86 may be patterned in a U shape or a zigzag shape. When the magnetic sensing parts 25, 35, 45, 55, 67, 74, 86 are formed in a U-shape and a zigzag shape, the elements of the magnetic sensing parts 25, 35, 45, 55, 67, 74, 86 The sum of the lengths of the portions facing the longitudinal direction is the element length L. When the magnetic sensitive parts 25, 35, 45, 55, 67, 74, 86 are formed in a U-shape or a bent shape, the magnetic sensitive parts 25, 35, 45, 55, 67, 74, 86 The extension direction of the longest straight line portion is the element longitudinal direction, and this direction coincides with the direction perpendicular to the excitation direction of the magnetic field generated by the drive AC current.
[0201]
The magnetic sensing portions 25, 35, 45, 55, 67, 74, 86 are formed, for example, with an element width W of 0.10 mm and an element length L of 6 mm. At this time, the aspect ratio of the magnetic sensitive portions 25, 35, 45, 55, 67, 74, 86 of the magneto-impedance effect element is W / L = 0.177.
[0202]
At this time, when the external magnetic field is applied to the longitudinal direction of the elements of the magnetosensitive parts 25, 35, 45, 55, 67, 74 and 86 after applying the magneto-impedance effect element, an external magnetic field is applied. The absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of 25, 35, 45, 55, 67, 74, and 86 is 400 (A / m) or less.
[0203]
By forming the magnetic sensitive portions 25, 35, 45, 55, 67, 74, 86 in a static magnetic field, the soft portions included in the magnetic sensitive portions 25, 35, 45, 55, 67, 74, 86 are provided. The shape magnetic anisotropy energy in the element longitudinal direction (X direction) and the magnetic anisotropy energy in the element width direction (Y direction) of the magnetic thin film can be substantially balanced. That is, as shown in FIG. 13, the total area of the magnetic domain 22b, which is a magnetic domain having a larger component in the element longitudinal direction, is equal to the total area of the magnetic domain 22a, which is a magnetic domain having a larger component in the element width direction. As shown in FIG. 14, the total area of the magnetic domains 22b having a larger component in the element longitudinal direction is equal to that of the magnetic domain 22a having a larger component in the element width direction. What has a magnetic domain structure larger than the total area is obtained.
[0204]
FIG. 20 is a configuration diagram showing the internal structure of the RF magnetron sputtering apparatus used in the present embodiment.
[0205]
As shown in FIG. 20, in the chamber 102 of the magnetron sputtering apparatus 101, an electrode part 105 for attaching the targets 103, 104 and a substrate holding part 106 are provided at positions facing the targets 103, 104. ing. A substrate 21 is placed on the substrate holding unit 106.
[0206]
The target 103 is made of a soft magnetic material, and the target 104 is made of a conductive material. In addition, a shielding plate 107 is provided between the target 103 and the target 104.
[0207]
A discharge magnet (not shown) is provided in the electrode portion 105, and an erosion region (not shown) is formed on the surfaces of the targets 103 and 104 by a magnetic field generated from the discharge magnet. .
[0208]
Further, the chamber 102 is provided with a gas introduction port 108 and a gas exhaust port 109, and Ar (argon) gas is introduced from the gas introduction port 108.
[0209]
When a high frequency is applied to the electrode unit 105 from a high frequency power source (RF power source) 110, a magnetron discharge is generated by the interaction between the electric field and the magnetic field, and the targets 103 and 104 are sputtered.
[0210]
When the substrate 21 on which the thin film is laminated is in the region A under the target 103 made of the soft magnetic material, the soft magnetic thin film is formed, and when it is in the region B under the target 104 made of the conductive material, the conductive material A thin film is formed.
[0211]
First, the substrate 21 is disposed in the region A under the target 103 made of a soft magnetic material. The substrate holder 106 rotates in the direction of the arrow. When the substrate holding unit 106 rotates, the soft magnetic thin film 22 is formed on the substrate 21, and the substrate 21 moves to the region B under the target 104 made of a nonmagnetic material. The thin film 23 is formed. The substrate holder 106 continues to rotate further, the substrate 21 moves again to the region A under the target 103, and the soft magnetic thin film 24 is formed on the conductive thin film 23, resulting in the state of FIG.
[0212]
Furthermore, by continuously operating the RF magnetron sputtering apparatus and continuing to rotate the substrate holding unit 106, it is possible to stack an arbitrary number of conductive thin films and soft magnetic thin films.
[0213]
In the case of performing film formation in a magnetic field, a magnet for applying a static magnetic field to the soft magnetic thin film being formed is provided with the substrate holder 106 interposed therebetween. The magnet is made of, for example, a hard magnetic material such as Sm—Co or an electromagnet.
[0214]
As the sputtering apparatus, in addition to the RF magnetron sputtering apparatus 101 as shown in FIG. 20, an existing apparatus such as an RF bipolar sputtering apparatus, an RF tripolar sputtering apparatus, an ion beam sputtering apparatus, or an opposed target sputtering apparatus is arbitrarily used. You can do it.
[0215]
In addition to the sputtering method, the soft magnetic thin film and the conductive thin film in the present invention may be formed by vapor deposition, MBE (molecular beam epitaxy), ICB (ion-cluster beam), or plating. May be used.
[0216]
Moreover, when forming the magnetic sensitive part 25 using a soft magnetic ribbon, the liquid quenching apparatus C shown in FIG. 21 is used, for example.
[0217]
First, an Fe—Co—Si—B-based soft magnetic material is put into a nozzle 111 made of quartz, and is heated and melted by a heater 112 provided around the nozzle 111. The molten alloy 113 is injected onto the cooling roll 114 rotating at a high speed by the pressure applied from the upper part of the nozzle, and the soft magnetic ribbon 115 is formed by contact quenching.
[0218]
The obtained soft magnetic ribbon 115 is cut into a substantially rectangular shape so that the ratio (aspect ratio) W / L of the element width W to the element length L is 0.1 or less. A conductive thin film is formed on at least one surface of the soft magnetic ribbon 115 by a method such as sputtering or vapor deposition.
[0219]
Next, at least two soft magnetic ribbons having the conductive thin film sequentially laminated on the substrate are bonded and laminated to form a magnetosensitive part, and then the magnetosensitive part is subjected to heat treatment in a static magnetic field in the element width direction. Call.
[0220]
Further, when electrode portions are formed at both ends of the magnetic sensitive portion, a magneto-impedance effect element as shown in FIG. 1 is obtained.
[0221]
22 to 25 are schematic views of the soft magnetic thin film 24 of the magnetosensitive part 25 of the magneto-impedance effect element shown in FIG. 1 observed with a Kerr effect polarization microscope and photographed.
[0222]
In FIG. 22, the magnetosensitive portion 25 is formed with a length L = 2 mm in the element longitudinal direction (X direction) and a length W = 100 μm in the element width direction (Y direction), that is, an aspect ratio W / L = 0.05. The magnetic domain structure of the soft magnetic thin film 24 is shown. 23 and 24, the magnetic sensitive portion 25 is formed with the length L in the element longitudinal direction L = 4 mm and the element width direction dimension W = 100 μm, that is, the aspect ratio W / L = 0.025. The magnetic domain structure is shown.
[0223]
22 and 23, the total area of the magnetic domains in which the magnetic moment is aligned in the element width direction and the total area of the magnetic domains in which the magnetic moment is aligned in the element longitudinal direction are in an antagonistic state. The magnetic anisotropy energy in the element width direction and the element longitudinal direction balance, and the direction of magnetic anisotropy is almost isotropic as a whole.
[0224]
In FIG. 24, the total area of the magnetic domains in which the magnetic moment is oriented in the element longitudinal direction is larger than the total area of the magnetic domains in which the magnetic moment is oriented in the element width direction. However, the magnetic anisotropy energy in the element width direction and the element longitudinal direction balance and the direction of magnetic anisotropy is almost isotropic as a whole.
[0225]
That is, in any of the soft magnetic thin films 24 shown in FIGS. 22 to 24, the magnetic moment is difficult to be fixed in a certain direction, and the direction of the magnetic moment is easily changed when excited by an alternating current. . That is, the magnetic permeability μ in the element width direction of the magnetic sensing portion 25 is increased, and the magnetic field detection sensitivity of the magneto-impedance effect element is increased. In addition, the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing unit 25 can be reduced, and the required magnitude of the bias magnetic field can be reduced.
[0226]
In FIG. 25, the magnetosensitive part is formed with a length L in the element longitudinal direction (X direction) of 4 mm and a length W in the element width direction (Y direction) of 500 μm, that is, an aspect ratio W / L = 0.125. The magnetic domain structure of the soft magnetic thin film 24 is shown.
[0227]
In FIG. 25, magnetic domains in which the magnetic moment is oriented in the element width direction dominate, and the direction of magnetic anisotropy faces the element width direction.
[0228]
That is, the magnetic permeability μ in the element width direction of the magnetic sensing portion is small, and the magnetic field detection sensitivity of the magneto-impedance effect element is small. In addition, the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing part is large, and the required bias magnetic field is also large.
[0229]
22 to 25 has a FeAlSiHfCRu-based composition, is formed of a microcrystalline soft magnetic alloy thin film mainly composed of bcc-Fe crystal grains, and the thickness of the magnetosensitive part. Is formed at 4 μm.
[0230]
22 to 25 show the magnetic domain structure of the soft magnetic thin film 24 in the uppermost layer of the magnetosensitive part 25 of the magneto-impedance effect element in FIG. 1, but the soft magnetic thin film 22 in the lowermost layer also has the same magnetic domain structure. Indicated.
[0231]
【Example】
26 and 27 are graphs showing the results of measuring the magnetoimpedance effect characteristics using the magnetoimpedance effect element shown in FIG.
[0232]
An external magnetic field Hex is applied in the element longitudinal direction of the magneto-impedance effect element M in a state where a driving AC current is applied to both ends of the magneto-sensitive part 25 from the electrode portions 26 and 26 of the magneto-impedance effect element M in FIG. The output voltage Emi was measured while changing the magnitude of the applied external magnetic field Hex.
[0233]
FIG. 26 shows that the magnetosensitive part is formed of a microcrystalline soft magnetic alloy thin film mainly composed of bcc-Fe crystal grains having a FeAlSiHfCRu-based composition, and the length of the magnetosensitive part 25 in the element longitudinal direction is 4 mm. This is a result when the thickness is 4 μm and the dimension in the element width direction is changed.
[0234]
Referring to FIG. 26, when the element width direction dimension of the magnetosensitive part 25 is 1000 μm (W / L = 0.25) and 500 μm (W / L = 0.125), the magnitude of the external magnetic field is changed. Sometimes there is almost no change in the output voltage, indicating that it does not function as a magnetic field sensor. The absolute value of the magnitude of the external magnetic field that maximizes the output voltage exceeds 400 (A / m).
[0235]
On the other hand, when the dimension in the element width direction of the magnetic sensing portion 25 is 100 μm (W / L = 0.025), the change in the output voltage becomes 200 mV or more at the maximum when the magnitude of the external magnetic field is changed. It can be seen that it functions as a sensitive magnetic field sensor. The absolute value of the magnitude of the external magnetic field that maximizes the output voltage is 160 (A / m).
[0236]
When the element width direction dimension of the magnetic sensitive portion 25 is 100 μm (W / L = 0.025), the soft magnetic thin film constituting the magnetic sensitive portion 25 has a single domain structure or a multi-domain structure. When the component in the element longitudinal direction of the magnetic moment in the magnetic domain is compared with the component in the element width direction, the total area of the magnetic domain in which the component in the element longitudinal direction is larger and the component of the magnetic domain in which the component in the element width direction is larger The total area of the magnetic domains having the same total area or the larger component in the element longitudinal direction is larger than the total area of the magnetic domains having the larger component in the element width direction.
[0237]
In FIG. 27, the magnetosensitive part 25 is formed of a microcrystalline soft magnetic alloy thin film having a FeAlSiHfCRu-based composition and mainly composed of bcc-Fe crystal grains, and the length of the magnetosensitive part 25 in the longitudinal direction of the element is 6 mm. The results are obtained when the thickness is 4 μm and the dimension in the element width direction is changed.
[0238]
Referring to FIG. 27, when the element width direction dimension of the magnetosensitive part 25 is 1000 μm (W / L = 0.17), the output voltage hardly changes when the magnitude of the external magnetic field is changed. It turns out that it does not function as a magnetic field sensor. The absolute value of the magnitude of the external magnetic field that maximizes the output voltage exceeds 400 (A / m).
[0239]
On the other hand, when the element width direction dimension of the magnetic sensing portion 25 is 500 μm (W / L = 0.08), the change in the output voltage is 50 mV or more at the maximum when the magnitude of the external magnetic field is changed. It can be seen that it can function as a sensor. The absolute value of the magnitude of the external magnetic field that maximizes the output voltage is 320 (A / m). Further, when the element width direction dimension of the magnetic sensing portion 25 is 100 μm (W / L = 0.177), the change of the output voltage becomes 600 mV or more at the maximum when the magnitude of the external magnetic field is changed. It can be seen that it can function as a highly sensitive magnetic field sensor. The absolute value of the magnitude of the external magnetic field that maximizes the output voltage is 0 to 24 (A / m).
[0240]
When the element width direction dimension of the magnetic sensing portion 25 is 500 μm or 100 μm, the soft magnetic thin film constituting the magnetic sensing portion 25 has a single domain structure or a multi-domain structure, and a magnetic moment element in each magnetic domain. When comparing the component in the longitudinal direction and the component in the element width direction, the total area of the magnetic domains having the larger component in the element longitudinal direction is equal to the total area of the magnetic domains having the greater component in the element width direction. In other words, the total area of magnetic domains having a larger component in the element longitudinal direction is larger than the total area of magnetic domains having a larger component in the element width direction.
[0241]
FIG. 28 shows the application of the aspect ratio and the external magnetic field of the magnetosensitive portion 25 using a magneto-impedance effect element in which the length of the magnetosensitive portion 25 in the element longitudinal direction is fixed to 3 mm and the element width direction dimensions are variously changed. It is a graph which shows the result of having investigated the relationship with the variation | change_quantity of the output voltage at the time of doing.
[0242]
The change amount of the output voltage shown in FIG. 28 is a change amount of voltage when the external magnetic field is changed by 320 (A / m).
[0243]
When the magneto-impedance effect element is used as a magnetic field sensor, it is preferable to set the output change amount in the graph of FIG. 28 to 100 mV or more. Therefore, it can be seen that the aspect ratio (W / L) of the magnetic sensitive portion is preferably 0.004 or more.
[0244]
In FIG. 28, the aspect ratio of the magnetosensitive portion when the output change amount takes the maximum value is 0.017.
[0245]
【The invention's effect】
As described above, according to the present invention described in detail, the magnetosensitive part of the magneto-impedance effect element has a structure in which the soft magnetic body part and the conductor part having a lower specific resistance than the soft magnetic body part are in contact with each other. Therefore, when a driving AC current is applied to the magnetic sensing part, the driving AC current flows in a manner divided into a current flowing in the soft magnetic body part and a current flowing in the soft magnetic body part, When the drive AC current flows, the DC resistance value of the magnetic sensing portion is reduced, and the power consumption of the magneto-impedance effect element can be reduced.
[0246]
In the present invention, since the magnetic sensitive part has a structure in which a soft magnetic part having a high magnetic permeability and a conductive part having a high conductivity are in contact with each other, the drive AC current flowing in the magnetic sensitive part can be reduced. The skin thickness is reduced and a large magneto-impedance effect can be generated. Therefore, a sufficient amount of change in the output voltage with respect to the magnetic field can be obtained even with a low driving voltage.
[Brief description of the drawings]
FIG. 1 is a perspective view of a magneto-impedance effect element showing a first embodiment of the invention,
FIG. 2 is a cross-sectional view of a magneto-impedance effect element showing a second embodiment of the present invention;
FIG. 3 is a sectional view of a magneto-impedance effect element showing a third embodiment of the present invention;
FIG. 4 is a sectional view of a magneto-impedance effect element showing a fourth embodiment of the present invention;
FIG. 5 is a cross-sectional view of a magneto-impedance effect element showing a fifth embodiment of the present invention;
FIG. 6 is a sectional view of a magneto-impedance effect element showing a sixth embodiment of the present invention;
[Fig. 7]Reference exampleThe perspective view of the magneto-impedance effect element which shows the form of
[Fig. 8]FIG.Sectional drawing of the magneto-impedance effect element which shows the form of
FIG. 9 is a graph showing the relationship between the aspect ratio of the magnetosensitive part of the magneto-impedance effect element and the magnetic field detection sensitivity;
FIG. 10 is a graph showing the relationship between the aspect ratio of the magnetic sensing part of the magneto-impedance effect element and the absolute value Hp of the magnitude of the external magnetic field that maximizes the output voltage Emi from both ends of the magnetic sensing part;
FIG. 11 is a conceptual diagram showing magneto-impedance effect characteristics of the magneto-impedance effect element of the present embodiment;
FIG. 12 is a conceptual plan view showing a magnetic domain structure of a magnetosensitive part of a magneto-impedance effect element;
FIG. 13 is a conceptual plan view showing a magnetic domain structure of a magnetosensitive part of a magneto-impedance effect element;
FIG. 14 is a conceptual plan view showing a magnetic domain structure of a magnetosensitive part of a magneto-impedance effect element;
FIG. 15 is a cross-sectional view showing a magneto-impedance effect element provided with a hard magnetic material layer for applying a bias magnetic field as an embodiment of the magneto-impedance effect element of the present invention;
FIG. 16 is a sectional view showing a magneto-impedance effect element provided with a hard magnetic material layer for applying a bias magnetic field as an embodiment of the magneto-impedance effect element of the present invention;
FIG. 17 is a sectional view showing a magneto-impedance effect element provided with an antiferromagnetic layer for applying a bias magnetic field as an embodiment of the magneto-impedance effect element of the present invention;
FIG. 18 is a perspective view showing a state in which a soft magnetic thin film and a conductive thin film serving as a magnetic sensitive part are formed on a substrate made of a nonmagnetic material such as alumina titanium carbide;
FIG. 19 is a perspective view showing a state in which a magnetic sensitive part is formed by patterning the multilayer film of FIG. 18 by photolithography and etching;
FIG. 20 is a cross-sectional view of an RF magnetron sputtering apparatus that can be used for carrying out the method of manufacturing a magneto-impedance effect element of the present invention;
FIG. 21 is a perspective view showing a liquid quenching device for forming a soft magnetic ribbon;
FIG. 22 is a schematic diagram of a magnetic sensing part of the magneto-impedance effect element of the present invention observed with a Kerr effect polarization microscope and photographed;
FIG. 23 is a schematic diagram of a magneto-sensitive effect element according to the present invention observed and photographed with a Kerr-effect polarization microscope;
FIG. 24 is a schematic diagram of a magnetosensitive effect element according to the present invention observed and photographed with a Kerr effect polarization microscope,
FIG. 25 is a schematic diagram of a magnetic sensing part of the magneto-impedance effect element of the present invention observed with a Kerr effect polarization microscope and photographed;
FIG. 26 is a graph showing measured values of magneto-impedance effect characteristics of the magneto-impedance effect element of the present invention;
FIG. 27 is a graph showing measured values of magneto-impedance effect characteristics of the magneto-impedance effect element of the present invention;
FIG. 28 is a graph showing the relationship between the aspect ratio of the magnetosensitive part of the magneto-impedance effect element and the output change amount;
FIG. 29 is a perspective view showing a conventional magneto-impedance effect element;
FIG. 30 is a circuit diagram showing a method for applying a driving AC current to a magneto-impedance effect element and applying an external magnetic field;
[Explanation of symbols]
21 Substrate
22, 24, 32, 34, 42, 44, 52, 54, 62, 64, 66, 72, 81, 85 Soft magnetic thin film
23, 33, 43, 53, 63, 65, 73, 83 Conductive thin film
25, 35, 45, 55, 67, 74, 86
26, 87 Electrode section

Claims (19)

In a magneto-impedance effect element provided on a substrate made of a non-magnetic material with a magneto-sensitive part having a magneto-impedance effect and an electrode part that gives a driving alternating current to the magneto-sensitive part,
The magnetic sensitive part has a soft magnetic part formed of a soft magnetic material, a conductor part having a lower specific resistance than the soft magnetic part, and the soft magnetic part and the conductor part are: At least partially touching ,
The ratio (aspect ratio) W / L of the element width W and the element length L of the magnetosensitive part is 0.1 or less,
The soft magnetic part has a single-domain structure or a multi-domain structure, and when the component in the element longitudinal direction of the magnetic moment in each magnetic domain is compared with the component in the element width direction, the component in the element longitudinal direction is more A magneto-impedance effect element , wherein a total area of large magnetic domains is equal to a total area of magnetic domains having a larger component in the element width direction . In a magneto-impedance effect element provided on a substrate made of a non-magnetic material, a magneto-sensitive part having a magneto-impedance effect, and an electrode part for applying a driving AC current to the magneto-sensitive part,
  The magnetic sensitive part has a soft magnetic part formed of a soft magnetic material, a conductor part having a lower specific resistance than the soft magnetic part, and the soft magnetic part and the conductor part are: At least partially touching,
  The ratio (aspect ratio) W / L of the element width W and the element length L of the magnetosensitive part is 0.1 or less,
The soft magnetic body portion has a single magnetic domain structure or a multi-domain structure, and when the component in the element longitudinal direction of the magnetic moment in each magnetic domain is compared with the component in the element width direction, the component in the element longitudinal direction is more A magneto-impedance effect element, wherein the total area of the large magnetic domains is larger than the total area of the magnetic domains having a larger component in the element width direction. The magneto-impedance effect element according to claim 1, wherein the soft magnetic body portion and the conductor portion are alternately laminated. 4. The magnetic impedance according to claim 3 , wherein the uppermost layer and the lowermost layer are the soft magnetic body portions, and the uppermost layer and the lowermost soft magnetic body portions are magnetically coupled at least at an end in the element width direction. Effect element. Element width dimension of the upper surface of the sensing section is a magnetic impedance effect element according to any one of the to short claims 1 than the element width direction dimension of the bottom surface of the magnetic sensitivity 4. The magneto-impedance effect element according to claim 5 , wherein the dimension of the element width direction gradually decreases as the magnetic sensing part moves away from the surface of the substrate.   The absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensitive part when an external magnetic field is applied in the longitudinal direction of the element of the magnetic sensitive part to which a driving AC current is applied is 400. The magneto-impedance effect element according to claim 1, wherein the magneto-impedance effect element is (A / m) or less.   The magneto-impedance effect element according to claim 7, wherein the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing part is 320 (A / m) or less.   The magneto-impedance effect element according to claim 7, wherein the absolute value of the magnitude of the external magnetic field that maximizes the output voltage from both ends of the magnetic sensing part is 160 (A / m) or less. 10. The magneto-impedance effect element according to claim 1, wherein a ratio (aspect ratio) W / L of an element width W and an element length L of the magnetosensitive part is 0.05 or less. 10. The magneto-impedance effect element according to claim 1, wherein a ratio (aspect ratio) W / L of an element width W and an element length L of the magnetosensitive part is 0.03 or less. Magneto-impedance effect element according to any one of claims 1 to 11 having a magnetic body for applying a bias magnetic field to the longitudinal direction of the element parallel to the direction of the magnetic sensitivity surfaces. The soft magnetic material part, represented by a compositional formula of Fe _h M _i O _j, the magneto-impedance effect element according to any one of claims 1 to 12 is microcrystalline soft magnetic alloy thin film mainly composed of amorphous structure.
However, M is one or more elements selected from Ti, Zr, Hf, V, Nb, Ta, W and rare earth elements, and h, i, and j are at% and 45 ≦ h ≦ 70. The relationship of 5 ≦ i ≦ 30, 10 ≦ j ≦ 40, h + i + j = 100 is satisfied. The soft magnetic material part, magnetic impedance according to any of the composition formula _{(Co 1-c T c)} x M y X z O claims 1 microcrystalline soft magnetic alloy thin film represented by _w 12 Effect element.
However, the element T is an element containing one or both of Fe and Ni, and the element M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Si, P, C, W, One or more elements selected from B, Al, Ga, Ge and rare earth elements, and X is one selected from Au, Ag, Cu, Ru, Rh, Os, Ir, Pt, Pd or It is an element of two or more, and the composition ratio is such that c is 0 ≦ c ≦ 0.7, x, y, z, and w are at%, 3 ≦ y ≦ 30, 0 ≦ z ≦ 20, 7 ≦ w The relationship of ≦ 40, 20 ≦ y + z + w ≦ 60 is satisfied, and the balance is x. The soft magnetic material part, represented by a compositional formula of _{T 100-defg X d M e} Z f Q g, and mainly bcc-Fe, bcc-FeCo, one or more of crystal grains of the bcc-Co magneto-impedance effect element according to any one of claims 1 to 12 the microcrystalline soft magnetic alloy thin film.
However, the element T is an element containing one or both of Fe and Co, the element X is an element containing either one or both of Si and Al, and the element M is Ti, Zr, One or more elements selected from Hf, V, Nb, Ta, Mo, and W. The element Z is an element including one or both of C and N. Q is Cr, It is one or more elements selected from Re, Ru, Rh, Ni, Pd, Pt, and Au, and d, e, f, and g are at%, and 0 ≦ d ≦ 25, 1 ≦ e ≦ 10 , 0.5 ≦ f ≦ 15 and 0 ≦ g ≦ 10 are satisfied. The soft magnetic material part, represented by a compositional formula of _{T 100-pqefg Si p Al q} M e Z f Q g, bcc-Fe, bcc-FeCo, one or more of crystal grains of the bcc-Co magneto-impedance effect element according to any one of claims 1 microcrystalline soft magnetic alloy thin film containing mainly 12.
However, the element T is an element containing one or both of Fe and Co, and the element M is one or more selected from Ti, Zr, Hf, V, Nb, Ta, Mo, and W. The element Z is an element containing one or both of C and N, and Q is one or two selected from Cr, Re, Ru, Rh, Ni, Pd, Pt, and Au. P, q, e, f, and g are at%, 8 ≦ p ≦ 15, 0 ≦ q ≦ 10, 1 ≦ e ≦ 10, 0.5 ≦ f ≦ 15, 0 ≦ g The relationship of ≦ 10 is satisfied. The soft magnetic material portion, composition formula _{(Fe 1-a Co a)} 100-xy (Si 1-b B b) according to claim 1 which is amorphous soft magnetic alloy thin film or ribbon represented by _x M _y Thru | or 12 magneto-impedance effect element in any one of.
However, M is an element containing one or both of Cr and Ru, and a and b representing the composition ratio are 0.05 ≦ a ≦ 0.1 and 0.2 ≦ b ≦ 0.8. , X and y satisfy the relationship of 10 ≦ x ≦ 35 and 0 ≦ y ≦ 7 in at%. The soft magnetic material part, represented by a compositional formula of Co _l Ta _m Hf _n, magneto-impedance effect element according to any one of claims 1 to 12 is an amorphous soft magnetic alloy thin film mainly the amorphous structure .
However, l, m, and n are at% and satisfy the relations of 70 ≦ l ≦ 90, 5 ≦ m ≦ 21, 6.6 ≦ n ≦ 15, and 1 ≦ m / n ≦ 2.5. The soft magnetic body section, the magneto-impedance effect element according to any one formula is Co _a Zr _b Nb claims 1 an amorphous soft magnetic alloy thin film mainly composed of amorphous structure represented by _c 12 .
However, a, b, and c are at% and satisfy the relationship of 78 ≦ a ≦ 91 and 0.5 ≦ b / c ≦ 0.8.

Images