JPH0577345B2 - - Google Patents
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- Publication number
- JPH0577345B2 JPH0577345B2 JP63089551A JP8955188A JPH0577345B2 JP H0577345 B2 JPH0577345 B2 JP H0577345B2 JP 63089551 A JP63089551 A JP 63089551A JP 8955188 A JP8955188 A JP 8955188A JP H0577345 B2 JPH0577345 B2 JP H0577345B2
- Authority
- JP
- Japan
- Prior art keywords
- oxide superconducting
- superconducting material
- magnetic memory
- magnetic
- oxide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- Crystals, And After-Treatments Of Crystals (AREA)
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Description
【発明の詳細な説明】
「発明の利用分野」
本発明は超伝導体、特に高い臨界温度（以下
Tcという）を有する酸化物超伝導体のバルクあ
るいは薄膜を用いて形成される超伝導素子に関す
る。特に酸化物超伝導体において生じる粒界や格
子欠陥を積極的に利用することに特徴を持つ超伝
導素子についてのものである。すなわち超伝導体
の粒界や格子欠陥に外部からの印加磁場の磁束が
トラツプされるという性質によつて動作する超伝
導記憶素子に関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention relates to superconductors, particularly those with high critical temperatures (
This invention relates to a superconducting device formed using a bulk or thin film of an oxide superconductor (referred to as Tc). In particular, it concerns superconducting elements that are characterized by the active use of grain boundaries and lattice defects that occur in oxide superconductors. In other words, it relates to a superconducting memory element that operates due to the property that the magnetic flux of an externally applied magnetic field is trapped in the grain boundaries and lattice defects of a superconductor.
「従来の技術」
超伝導体の特異な磁気的性質を利用した記憶素
子には、従来、トンネル型やマイクロブリツジ型
のジヨセフソン接合を用いて外部からの印加磁場
をトラツプすることによつて記憶する素子が知ら
れていた。しかし、これらの従来素子はTcの低
い（約30K付近）ニオブ等の材料が使われていた
ため、液体ヘリウムが必要でコストがかかりすぎ
るという問題があつた。一方、近年液体窒素温度
以上の高温で超伝導を示す酸化物超伝導体（例え
ばYBa2Cuu3O7-xやBi2（Sr、Ca）3Cu2O9-x等）が
発見され、これらをデバイスに利用する研究がな
されている。``Prior art'' Storage elements that utilize the unique magnetic properties of superconductors have conventionally used tunnel-type or microbridge-type Josephson junctions to trap externally applied magnetic fields. Elements that do this were known. However, these conventional elements used materials such as niobium that had a low Tc (approximately 30K), so they required liquid helium, which was costly. On the other hand, in recent years, oxide superconductors (such as YBa 2 Cuu 3 O 7-x and Bi 2 (Sr, Ca) 3 Cu 2 O 9-x ) that exhibit superconductivity at temperatures above liquid nitrogen temperature have been discovered. Research is being conducted to utilize these in devices.
しかしながら、これらの酸化物超伝導体は高温
（500℃以上）での加工処理が必要が必要であるば
かりか、他の金属・非金属元素と非常に反応し易
いため、数百オングストロームのサイズのジヨセ
フソン接合をこの酸化物超伝導体を用いて、形成
することは非常に困難であつた。 However, these oxide superconductors not only require high-temperature processing (above 500°C) but also react very easily with other metals and non-metallic elements, so they cannot be fabricated with a size of several hundred angstroms. It was extremely difficult to form a Josephson junction using this oxide superconductor.
「発明の構成」
本発明人はこの酸化物超伝導体において外部か
ら磁場を印加すると酸化物超伝導体の粒界に磁束
が侵入し、印加磁場を取り去つた後でも磁束がト
ラツプされているという現象を見出した。さら
に、このような状態では侵入した磁束によつて超
伝導経路が狭められ超伝導臨界電流値が大きく減
少し、比較的小さな電流によつても電圧を生じる
こと、および、この状態は印加磁場を取り去つた
後でも変わらないことを発見した。このような現
象は超伝導特性のよくない試料ほど顕著であるこ
とが分り、本発明人はその原因が格子欠陥である
と考えた。さらに、本発明人は磁性に敏感な格子
欠陥を導入することによつて磁束をより強く安定
にトラツプできることを見いだした。そこで、そ
のような条件を満たす格子欠陥を導入するために
酸化物超伝導体の構成元素である銅を、他の遷移
金属で磁性を示し、かつ、銅のサイトに置換しう
る元素で置き換えることを考案した。その結果わ
ずか10ガウスの外部磁場によつて抵抗を発生し、
磁場を取り去つた後もひきつづき抵抗を示す素子
を再現性よく作成することが出来た。これによつ
て酸化物超伝導体においてもジヨセフソン接合を
用いたのと同様な記憶素子を作成することができ
た。以下実施例を示し動作原理等に詳細に説明す
る。"Structure of the Invention" The present inventor discovered that when an external magnetic field is applied to this oxide superconductor, magnetic flux invades the grain boundaries of the oxide superconductor, and even after the applied magnetic field is removed, the magnetic flux is trapped. We discovered this phenomenon. Furthermore, in such a state, the superconducting path is narrowed by the invading magnetic flux, and the superconducting critical current value is greatly reduced, and even a relatively small current generates a voltage. I discovered that it didn't change even after I removed it. It was found that such a phenomenon was more pronounced in samples with poor superconducting properties, and the inventors believed that the cause was lattice defects. Furthermore, the inventors have discovered that magnetic flux can be trapped more strongly and stably by introducing lattice defects that are sensitive to magnetism. Therefore, in order to introduce lattice defects that meet these conditions, it is necessary to replace copper, which is a constituent element of the oxide superconductor, with an element that exhibits magnetism in other transition metals and can substitute at copper sites. devised. As a result, an external magnetic field of only 10 Gauss creates resistance,
We were able to create an element with good reproducibility that continues to exhibit resistance even after the magnetic field is removed. As a result, it was possible to create a memory element similar to that using a Josephson junction using an oxide superconductor. Examples will be shown below and the operating principles will be explained in detail.
実施例 １
原材料として酸化イツトリウム（Y2O3）、炭酸
バリウム（BaCO3）、酸化銅（CuO）、酸化鉄
（Fe2O3）の粉末（いずれも純度は99.99％）をイ
ツトリウムバリウム、銅、鉄各原子のモル比が
１：２：2.9：0.1となるようにはかりと混合し
た。十分に混合した後、空気中900℃で12時間焼
成した。焼成後、反応生成物をとりだし、細かく
粉砕し、1000Kg/cm2圧力でペレツトに成形した。
このペレツトを再び、空気中900℃で３時間焼結
した後、10℃／minで徐冷した。このペレツトか
ら10mm×１mm×１mmの直方体を切出し、銀ペース
トで電極をつけた。４端子法による抵抗測定の結
果、第１図のような抵抗−温度曲線が得られた。
これを第２図のようにコイルの横に置きコイルと
試料は液体窒素中に置いた。コイルに電流を流さ
ない時の試料の電圧−電流曲線は第３図ａで示さ
れた。次にコイルに電流を流して試料に磁場を印
加したところ電圧−電流曲線は第３図ｂのように
なつた。このとき試料表面の磁場の強さは10ガウ
スであつた。さらに、コイルに流れている電流を
切り、試料に磁場がかからないようにしたときの
電圧−電流曲線は第３図ｃのようになつた。この
特性はコイルの電流を切つて数時間放置しても変
わらなかつた。Example 1 As raw materials, powders of yttrium oxide (Y 2 O 3 ), barium carbonate (BaCO 3 ), copper oxide (CuO), and iron oxide (Fe 2 O 3 ) (all purity 99.99%) were used as yttrium barium, Copper and iron were mixed in a balance so that the molar ratio of each atom was 1:2:2.9:0.1. After thorough mixing, it was baked in air at 900°C for 12 hours. After calcination, the reaction product was taken out, finely pulverized, and formed into pellets at a pressure of 1000 Kg/cm 2 .
This pellet was sintered again in air at 900°C for 3 hours, and then slowly cooled at 10°C/min. A rectangular parallelepiped of 10 mm x 1 mm x 1 mm was cut out from this pellet and electrodes were attached with silver paste. As a result of resistance measurement using the four-terminal method, a resistance-temperature curve as shown in FIG. 1 was obtained.
This was placed next to the coil as shown in Figure 2, and the coil and sample were placed in liquid nitrogen. The voltage-current curve of the sample when no current is applied to the coil is shown in Figure 3a. Next, when a current was passed through the coil and a magnetic field was applied to the sample, the voltage-current curve became as shown in Figure 3b. At this time, the strength of the magnetic field on the sample surface was 10 Gauss. Furthermore, when the current flowing through the coil was cut off so that no magnetic field was applied to the sample, the voltage-current curve became as shown in Figure 3c. This characteristic remained unchanged even after the coil current was turned off and the coil was left for several hours.
この現象は次のように理解できる。即ち、外部
磁場の印加によつて磁束が侵入し、磁性イオンで
ある鉄イオンと磁束との相互作用によつて局所的
な磁気的秩序が形成されその部分は非超伝導化す
る。これによつて超伝導電流の経路が狭まり臨界
電流値が大きく減少するそのため磁場をかけなか
つたときには抵抗はゼロ、磁場をかけると有限の
抵抗が発生するまた、一旦侵入した磁束は超伝導
体内にトラツプされてしまうので、外部磁場を絶
つた後も抵抗が残る磁性イオンを銅イオンの位置
に置いたのはそこが超伝導電流の通路だからであ
る。かくして、一度弱い磁場を印加するだけで半
永久的に記憶が保たれる素子を製作することが出
来た。この素子は、定電流を流すことによつて電
圧が生ずれば“１”、電圧が生じなければ“０”
としてデジタル記憶素子として動作する。記憶は
素子をTc以上の温度にすることによつて簡単に
消すことが出来る。 This phenomenon can be understood as follows. That is, magnetic flux enters by applying an external magnetic field, and local magnetic order is formed by the interaction between iron ions, which are magnetic ions, and the magnetic flux, and that part becomes non-superconducting. This narrows the path of the superconducting current and greatly reduces the critical current value.Therefore, when no magnetic field is applied, the resistance is zero, and when a magnetic field is applied, a finite resistance is generated.Furthermore, once the magnetic flux has entered the superconductor, The reason why magnetic ions, which will remain trapped and have some resistance even after the external magnetic field is cut off, was placed in the position of the copper ions is because this is the path for the superconducting current. In this way, we were able to create an element that retains memory semi-permanently by simply applying a weak magnetic field once. This element is "1" if a voltage is generated by flowing a constant current, and "0" if no voltage is generated.
It operates as a digital storage element. Memory can be easily erased by heating the element to a temperature above Tc.
実施例 ２
YBa2Cu2.9Fe0.1O7-x薄膜を用いて上述の素子を
作成した。薄膜はrfスパツタ法によつて酸化マグ
ネシウム単結晶状に形成され、Tcは80Kであつ
た。この薄膜を機械的にパターニングして長さ10
mm、幅0.2mmの短冊状にして電極を付け、磁場印
加における電圧−電流特性を調べた結果実施例１
と同様な特性を示した。Example 2 The above device was fabricated using a YBa 2 Cu 2.9 Fe 0.1 O 7-x thin film. The thin film was formed in the form of a magnesium oxide single crystal by the RF sputtering method, and its Tc was 80K. This thin film was mechanically patterned to a length of 10
Example 1 Results of investigating the voltage-current characteristics when applying a magnetic field by attaching electrodes to strips of 0.2 mm width and 0.2 mm width.
showed similar characteristics.
「効果」
本発明構成により、酸化物超伝導体によつて、
新規な不揮発性を有するメモリーを現実すること
が可能となつた。"Effect" With the configuration of the present invention, the oxide superconductor provides
It has become possible to realize a new non-volatile memory.
第１図 素子の抵抗−温度曲線、第２図 素子
とコイルの配置、第３図 素子の電流−電圧曲
線、ａ…磁場を印加する前、ｂ…磁場（10ガウ
ス）を印加しているとき、ｃ…磁場を取り去つた
後。
Fig. 1 Resistance-temperature curve of the element, Fig. 2 Arrangement of the element and coil, Fig. 3 Current-voltage curve of the element, a... before applying a magnetic field, b... when applying a magnetic field (10 Gauss) , c... after removing the magnetic field.
Claims (1)
料を用いた超伝導磁気メモリーであつて、 前記酸化物超伝導材料はその構成元素である銅
の一部が他の遷移金属でありかつ磁性を持つ元素
によつて置き換えられており、 前記超伝導磁気メモリーは、前記酸化物超伝導
材料に磁場を印加する手段と、 前記酸化物超伝導材料に電流を流す手段と、 前記電流により生じる電圧を検出する手段と、 を有していることを特徴とする超伝導磁気メモリ
ー。 ２ 構成元素である銅の一部が他の遷移金属であ
りかつ磁性を持つ元素によつて置き換えられて構
成されている酸化物超伝導材料を用いた超伝導磁
気メモリーの動作方法であつて、 前記磁気メモリーに情報を読み込ませるため
に、前記酸化物超伝導材料に磁場を印加し、前記
酸化物超伝導材料中に磁束をトラツプさせる動作
と、 前記磁気メモリーから情報を読みだすために、
前記酸化物超伝導材料に電流を流し、前記酸化物
超伝導材料中の前記磁束がトラツプされた領域に
電圧を生じさせ該電圧を検出する動作と、 を有することを特徴とする超伝導磁気メモリーの
動作方法。 ３ 超伝導磁気メモリーの作製方法であつて、 銅をその構成元素として含む酸化物超伝導材料
を、その構成元素である銅の一部を他の遷移金属
で磁性を持つ元素で置き換えて形成する工程と、 前記酸化物超伝導材料に磁場を印加する手段を
形成する工程と、 前記酸化物超伝導材料に電流を流す手段を形成
する工程と、 前記酸化物超伝導材料において電圧を検出する
手段を形成する工程と、 を有することを特徴とする超伝導磁気メモリーの
作製方法。[Scope of Claims] 1. A superconducting magnetic memory using an oxide superconducting material containing copper as a constituent element, wherein the oxide superconducting material has a part of its constituent copper that undergoes other transitions. The superconducting magnetic memory is replaced by an element that is a metal and has magnetism, and the superconducting magnetic memory includes means for applying a magnetic field to the oxide superconducting material, and means for passing an electric current through the oxide superconducting material. A superconducting magnetic memory comprising: means for detecting a voltage generated by the current. 2. A method of operating a superconducting magnetic memory using an oxide superconducting material in which a part of the constituent copper is replaced by another transition metal and magnetic element, comprising: In order to read information into the magnetic memory, a magnetic field is applied to the oxide superconducting material to trap magnetic flux in the oxide superconducting material; and in order to read information from the magnetic memory,
A superconducting magnetic memory comprising the following steps: passing a current through the oxide superconducting material, generating a voltage in a region in the oxide superconducting material where the magnetic flux is trapped, and detecting the voltage. How it works. 3. A method for producing a superconducting magnetic memory, in which an oxide superconducting material containing copper as a constituent element is formed by replacing a part of the constituent copper with a magnetic element of another transition metal. a step of forming a means for applying a magnetic field to the oxide superconducting material; a step of forming a means for passing a current through the oxide superconducting material; and a step of detecting a voltage in the oxide superconducting material. A method for producing a superconducting magnetic memory, comprising: a step of forming a superconducting magnetic memory;
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63089551A JPH01260867A (en) | 1988-04-12 | 1988-04-12 | Superconducting magnetic memory |
| US07/719,040 US5377141A (en) | 1988-04-12 | 1991-06-21 | Superconducting magnetic memory device having intentionally induced non-superconducting regions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63089551A JPH01260867A (en) | 1988-04-12 | 1988-04-12 | Superconducting magnetic memory |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01260867A JPH01260867A (en) | 1989-10-18 |
| JPH0577345B2 true JPH0577345B2 (en) | 1993-10-26 |
Family
ID=13973959
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63089551A Granted JPH01260867A (en) | 1988-04-12 | 1988-04-12 | Superconducting magnetic memory |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01260867A (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61195390A (en) * | 1985-02-26 | 1986-08-29 | 株式会社島津製作所 | Superconducting shield body |
| JPS61287181A (en) * | 1985-06-13 | 1986-12-17 | Nec Corp | Josephson integrated circuit |
-
1988
- 1988-04-12 JP JP63089551A patent/JPH01260867A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01260867A (en) | 1989-10-18 |
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