JP3585629B2 - Magnetoresistive element and magnetic information reading method - Google Patents
Magnetoresistive element and magnetic information reading method Download PDFInfo
- Publication number
- JP3585629B2 JP3585629B2 JP06958196A JP6958196A JP3585629B2 JP 3585629 B2 JP3585629 B2 JP 3585629B2 JP 06958196 A JP06958196 A JP 06958196A JP 6958196 A JP6958196 A JP 6958196A JP 3585629 B2 JP3585629 B2 JP 3585629B2
- Authority
- JP
- Japan
- Prior art keywords
- ferromagnetic
- ferromagnetic conductive
- magnetization
- conductive layer
- layer
- 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
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/3254—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
Description
【０００１】
【発明の属する技術分野】
本発明は磁気抵抗効果素子及びこれを用いた磁気情報読み出し方法に関する。
【０００２】
【従来の技術】
１９８８年に、磁性体と非磁性金属を積層した金属人工格子膜において、巨大な磁気抵抗効果が現れることが発見され（Ｂａｉｂｉｃｈ 他、Ｐｈｙｓ． Ｒｅｖ． Ｌｅｔｔ． ６１ （１９８８）２４７２頁〜２４７５頁）、それ以来、この現象に関連した研究がさかんになされるようになってきた。
【０００３】
最近は、これらの巨大な磁気抵抗を示す人工格子膜を用いた様々な応用が研究されており、例えば、磁気センサーや記録素子としての応用研究があり、特に、高速かつ高密度で不揮発メモリとして利用したもの（ＭＲＡＭ）が注目されている。
【０００４】
また、トンネル絶縁膜を介して磁性層を積層した強磁性トンネル接合でも磁気抵抗効果がみいだされている。
例えば、ＦｅとＡｌ２ Ｏ３ を用いた強磁性トンネル接合において両側のＦｅ膜の保磁力が異なるように作成されている場合、磁化過程中に両側のＦｅ膜の磁化が平行状態から反平行状態に変化し、トンネル抵抗が変化することで磁気抵抗効果が生じることが示されている（宮崎ら、Ｊｏｕｒｎａｌ ｏｆ Ｍａｇｎｅｔｉｓｍ ａｎｄ Ｍａｇｎｅｔｉｃ Ｍａｔｅｒｉａｌｓ １３９（１９９５） Ｌ２３１−Ｌ２３４ ）。特にこの系では、室温においても２０％以上の大きな磁気抵抗効果がある。
【０００５】
また、最近Ｍｏｏｄｅｒａ ら（Ｐｈｙｓ． Ｒｅｖ． Ｌｅｔｔ． ７４（１９９５）３２７３ 頁〜３２７６頁）によりＣｏＦｅ／Ａｌ２ Ｏ３ ／Ｃｏという組み合わせの強磁性トンネル接合においても接合の作成方法を改良することで、室温で１０％以上の磁気抵抗が得られることが示されている。
【０００６】
このように、強磁性トンネル接合に関しても大きな磁気抵抗効果が得られるようになってきたが、これについての応用研究はいまだほとんどなされておらず、磁気センサーや情報記憶素子としての応用例はほとんど報告されていない。
【０００７】
【発明が解決しようとする課題】
この様に強磁性トンネル接合の磁気抵抗効果を用いた応用、特に記録素子としての応用は検討されてはいない状況にある。
本発明は以上の点を考慮してなされたもので、強磁性トンネル接合を用いて、非破壊若しくは多値の記録／読出しが行なえる新規な磁気抵抗効果素子及び磁気情報読み出し方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明は、第１の強磁性導電層と、第２の強磁性導電層と、前記第１及び第２の強磁性導電層の間に介在する第１のトンネル絶縁層と、第３の強磁性導電層と、前記第２及び第３の強磁性導電層の間に介在する第２のトンネル絶縁層と、前記第１及び第３の強磁性導電層の外側にそれぞれ設けられた第１及び第２の反強磁性層とを具備し、前記第２の強磁性導電層の保磁力が前記第１及び第３の強磁性導電層の保磁力よりも小さく、前記第１乃至第３の強磁性導電層のうちの隣り合う層の磁化の向きが実質的に互いに同じかまたは逆であることを特徴とする磁気抵抗効果素子である。例えば、前記第１及び第３の強磁性導電層の磁化の向きが実質的に互いに同じであり、前記第２の強磁性導電層の磁化の向きが前記第１及び第３の強磁性導電層の磁化の向きと実質的に互いに同じかまたは逆である磁気抵抗効果素子である。
【０００９】
また、本発明は、第１の強磁性導電層と、第２の強磁性導電層と、前記第１及び第２の強磁性導電層の間に介在する第１のトンネル絶縁層と、第３の強磁性導電層と、前記第２及び第３の強磁性導電層の間に介在する第２のトンネル絶縁層と、前記第１及び第３の強磁性導電層の外側にそれぞれ設けられた第１及び第２の反強磁性層とを備え、前記第２の強磁性導電層の保磁力が前記第１及び第３の強磁性導電層の保磁力よりも小さく、前記第１乃至第３の強磁性導電層のうちの隣り合う層の磁化の向きが実質的に互いに同じかまたは逆である磁気抵抗効果素子の磁気情報読み出し方法であって、前記第２の強磁性導電層の磁化の向きを変化可能とし、前記第１及び第２のトンネル絶縁層を流れるトンネル電流に基づいて、前記第１乃至第３の強磁性導電層それぞれの磁化の向きの相対的関係を磁気情報として読み出すことを特徴とする磁気情報読み出し方法である。例えば、前記第１及び第３の強磁性導電層の磁化の向きが実質的に互いに同じであり、前記第２の強磁性導電層の磁化の向きが前記第１及び第３の強磁性導電層の磁化の向きと実質的に互いに同じかまたは逆であり、前記第１及び第３の強磁性導電層の磁化の向きと前記第２の強磁性導電層の磁化の向きとの相対的関係を磁気情報として読み出す磁気情報読み出し方法である。
【００１０】
【発明の実施の形態】
図１を用いて本発明の原理を説明する。磁性積層体（６）は、第１の強磁性導電層（１），第１のトンネル絶縁層（２），第２の強磁性導電層（３），第２のトンネル絶縁層（４）及び第３の強磁性導電層（５）が順次積層された構造を採る。
【００１１】
ここでは第２の強磁性導電層が（３）の保磁力が、第１及び第３の強磁性導電層（１）（５）の保磁力より小さいものとする。
磁気記録は第１及び第３の強磁性導電層（１）（５）を同じ方向に磁化することで行う。この図では上向きの磁化状態を“０”，下向きの磁化状態を“１”とする。
【００１２】
第２の強磁性導電層（３）の磁化の向きは不定である。ただし第２の強磁性導電層（３）の保磁力（Ｈ２ ）は第１及び第３の強磁性導電層の保磁力（Ｈ１ ， Ｈ３ ）よりも小とする。すなわちＨ１ ，Ｈ３ ＞Ｈ＞Ｈ２ の磁化を印加することで中間に位置する第２の強磁性導電層（３）の磁化方向のみを制御することができる。
【００１３】
まず“０”の状態の読み出しである。
電流磁界を用いて第２の強磁性導電層の磁化の向きを制御するものとする。すなわちこの磁性積層体に近接して導体格を設け、これに電流を流すことで磁界を印加するのである。正パルスをいれた場合は“０”と同方向に、負パルスをいれた場合は“１”と同方向に磁化の向きが定まるとする。
【００１４】
正パルスを入力する前の第２の強磁性導電層の磁化の向きは不定であるが、便宜上“０”と同方向であるとする。なお必要に応じ正パルスを印加して初期状態を“０”の向きにしておいても良い。また逆でも良い。
【００１５】
正パルスを印加した場合、第１，第２及び第３の強磁性導電層の磁化は同方向となり、磁性積層体（６）にはトンネル電流が流れ易くなる。一方、負パルスを印加した場合は、第１及び第２の強磁性導電膜の磁化に向きは逆であり、また第２及び第３の強磁性導電膜の磁化の向きは逆である。従って磁性積層体にはトンネル電流が非常に流れ難くなる。
【００１６】
図１（ａ）には正負パルス印加のタイミングを示し、図１（ｂ）は“０”の記録をもっている場合の磁化の向きを示し、それに伴い図１（ｃ）はトンネル電流の大きさを示す。正パルスを印加した時はトンネル電流が流れ、負パルスを印加した時はトンネル電流が流れ難いことを示している。この図では正パルスと負パルス間を離しているが、連続させても良い。
【００１７】
同図では正負パルスがないときの第２の強磁性導電層の磁化の向きは直前にかけられたパルスの状態が保持されることにしているが、第１及び第３の強磁性導電層との静磁接合等の影響で反転する可能性もある。従って、正負パルス印加時のトンネル電流を検出すれば良い。なお、電圧検出を行えば図１（ｃ）のチャートは逆になることは言うまでもない。
【００１８】
“１”の場合は“０”と逆で（図１（ｄ），（ｅ））、トンネル電流が小から大に変化することになる。
“０”，“１”の場合夫々正パルスを印加したときの磁性積層体（６）の両端に生じる電圧を基準とすれば、上述の例で電圧が上昇する場合（＋ΔＶの変位）は“０”、下降する場合（−ΔＶの変位）は“１”と判断できる。すなわち出力の絶対量ではなく変位の符号で“０”，“１”が判断でき、Ｓ／Ｎ比に優れた読出しが可能になる。
【００１９】
更に、この場合非破壊の読出しができる。
図２に３値データ“０”（図２（ｂ）（ｃ）），“１”（図２（ｄ）（ｅ）），“２”（図２（ｆ）（ｇ））を再生する場合について説明する。
【００２０】
例えば、第１及び第３の強磁性導電層の磁化の向きが上向きの場合を“０”，下向きの場合を“２”，異なる場合を“１”とする。図１の例と同様に第２の強磁性導電層の磁化の向きは上向きを初期状態とする。図２（ａ）に外部磁場発生用の電流パルスの例を示し、図１と同様に同図（ａ）（ｅ）（ｇ）はタイミングをあわせて記載されている。
【００２１】
正パルスを印加して第２の強磁性導電層の磁化を上向きとした場合、“０”のときは第１乃至第３の強磁性導電層の磁化がそろうのでトンネル電流が流れ易くなり、出力電圧は低く（ＶＬ ）、その他の場合は磁化がそろっていないのでトンネル電流が流れにくくなり、出力電圧は高く（ＶＨ ）なる。
【００２２】
続いて負パルスを印加した場合、“２”のときは下向きに磁化がそろいＶＬ となるが、その他はＶＨ となる。
従って、正負のパルスを加えた場合、ＶＬ →ＶＨ となる場合が“０”、ＶＨ →ＶＨ となる場合が“１”、ＶＨ →ＶＬ となる場合が“２”と判断できる。
【００２３】
この様に多値記録も可能である。しかも、読み出し前後で第１及び第３の強磁性導電層のスピンの向きは変わらず非破壊の読み出しができる。
第３に４値データ“０”（図３（ｂ）（ｃ）），“１”（図３（ｄ）（ｅ）），“２”（図３（ｆ）（ｇ）），“３“（図３（ｈ）（ｉ））を再生する場合について説明する。
【００２４】
例えば、第１及び第３の強磁性導電層の磁化の向きが上向きの場合を“０”，下向きの場合を“３”，異なる場合を第１の強磁性層の磁化が上向きのとき“１”下向きのときを“２”とする。
【００２５】
図１の例と同様に第２の強磁性導電層の磁化の向きは上向きを初期状態とする。図３（ａ）に外部磁場発生用の電流パルスの例を示し、図２と同様に同図（ａ）（ｅ）（ｇ）（ｉ）はタイミングをあわせて記載されている。
【００２６】
なお、図１，２の場合、Ｈ１ ，Ｈ３ ＞Ｈ（読み出し）＞Ｈ２ であったが、Ｈ１ ＞Ｈ３ の関係を更に付加する。更に読み出し用として振幅小と大を用意し、Ｈ１ ＞Ｈ（大）＞Ｈ３ ＞Ｈ（小）＞Ｈ２ とする。
【００２７】
正パルス（振幅小）を印加して第２の強磁性導電層の磁化を上向きとした場合、“０”のときは第１乃至第３の強磁性導電層の磁化がそろうのでトンネル電流が流れ易くなり、出力電圧は低く（ＶＬ ）、その他の場合は磁化がそろっていないのでトンネル電流が流れにくくなり、出力電圧は高く（ＶＨ ）なる。
【００２８】
続いて負パルスを印加した場合、“４”のときは下向きに磁化がそろいＶＬ となるが、その他はＶＨ となる。
更に正パルス（大）を印加すると第３の強磁性層は記録状態によらず上向きとなるので“２”“３”以外はＶＨ となる。
【００２９】
従って、正（小）負正（大）のパルスを加えた場合、ＶＬ →ＶＨ →ＶＬ となる場合が“０”、ＶＨ →ＶＨ →ＶＬ となる場合が“１”，ＶＨ →ＶＨ →ＶＨ が“２”，ＶＨ →ＶＬ →ＶＨ となる場合が“３”と判断できる。
【００３０】
この様に破壊読出しではあるが４値記録も可能である。
本発明素子は例えば以下の様にして作成される。
強磁性層として、Ｆｅ、Ｃｏ、Ｎｉ等の強磁性体やパーマロイ等の磁性合金、あるいは、ホイスラー合金等の半金属を用い、絶縁体層としてＮｉＯ、Ａｌ２ Ｏ３ などの酸化物を用いることができる。ここで、強磁性層の膜厚は１ｎｍから５００ｎｍが好ましく、絶縁層の膜厚は１ｎｍから４０ｎｍが好ましい。
【００３１】
接合の作成方法を、強磁性層としてＦｅ、絶縁体層としてＡｌ２ Ｏ３ を用いた場合について説明すると以下のようになる。
強磁性トンネル接合をガラス基板上に作成する。強磁性層はイオンビームスパッタ法により作成する。この際、チェンバ内を１×１０−６Ｔｏｒｒ以下の真空状態とした後、Ａｒを１×１０−４Ｔｏｒｒ導入し、Ａｒイオンの加速電圧を６００Ｖとして製膜を行う。また、第１と第３の強磁性層の膜厚は１００ｎｍ、第２の強磁性層の膜厚は５０ｎｍとして、第２の強磁性層の保磁力が第１と第３の強磁性層の保磁力より小さくなるようにした。絶縁体層は、Ａｌをイオンビームスパッタ法により膜厚５ｎｍから２５ｎｍに製膜し、大気中で２４時間自然酸化させてＡｌ２ Ｏ３ を形成する。
【００３２】
接合の作成方法を、強磁性層としてＦｅ、絶縁体層としてＡｌ２Ｏ３を用いた場合について説明すると以下のようになる。強磁性トンネル接合をガラス基板上に作成する。強磁性層はイオンビームスパッタ法により作成する。この際、チェンバ内を１×１０−６Torr以下の真空状態とした後、Ａｒを１×１０−４Torr導入し、Ａｒイオンの加速電圧を６００Ｖとして製膜を行う。また、第１と第３の強磁性層の膜厚は１００ｎｍ、第２の強磁性層の膜厚は５０ｎｍとして、第２の強磁性層の保磁力が第１と第３の強磁性層の保磁力より小さくなるようにした。絶縁体層は、Ａｌをイオンビームスパッタ法により膜厚５ｎｍから２５ｎｍに製膜し、大気中で２４時間自然酸化させてＡｌ２Ｏ３を形成する。
【００３３】
一層の絶縁体によって分けられた２種の強磁性層からなる強磁性トンネル接合については、Ｓｌｏｎｃｚｅｗｓｋｉ により理論的解析が行われている（Ｐｈｙｓ． Ｒｅｖ． Ｂ３９ （１９８９）６９９５頁〜７００２頁）。これによると、トンネルコンダクタンス（Ｇ）は、絶縁体が無限に厚い極限では接合の透過係数に比例する。
【００３４】
すなわち、Ｇは（１＋εｃｏｓ θ）に比例する。θは二つの強磁性層の磁化のなす角度を表わし、εは物質に依存した定数であり、０＜ε≦１の値をとる。従って、強磁性層の磁化が平行の時（θ＝０）コンダクタンスが最大値をとり、反平行のとき（θ＝π）最小値となる。ホイスラー合金などの半金属を用いた場合はε＝１である。
【００３５】
本発明では、強磁性層が３層含まれており、二つのトンネル接合の組み合わせとなっている。全体の透過係数は、各トンネル接合の透過係数により表すことができ、特に、各トンネル接合の透過係数Ｔが小さい場合には、Ｔのトータルは Ｔ２ に比例する。
【００３６】
従って、トンネル・コンダクタンス（Ｇｔｏｔａｌ ）は（１＋εｃｏｓ θ）２ に比例することになる。
従って３層の磁性層を有する方が磁場に関するコンダクタンスの微係数が大きくなることがわかる。図４にε＝１の場合に比例係数を正規化して示す。従って、磁場の変化に対するトンネル電流の変化の検出が容易になり、磁気センサーに適している。
【００３７】
さらに、第１と第３の強磁性層の磁化への外部磁場からの影響を小さくするために外側にＦｅＭｎのような反強磁性層を備えて、これらとの相互作用により第１と第３の強磁性層の磁化を固着することも考えられる。
【００３８】
【発明の効果】
以上説明したように本発明によれば強磁性トンネル接合を用いた新規な磁気抵抗効果素子を得ることができ、多値若しくは非破壊読出しが可能な磁気記録方式を得ることができる。
【図面の簡単な説明】
【図１】本発明の概略図。
【図２】本発明の概略図。
【図３】本発明の概略図。
【図４】本発明の特性図。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetoresistance effect element and a method for reading magnetic information using the same.
[0002]
[Prior art]
In 1988, it was discovered that a giant magnetoresistance effect appeared in a metal artificial lattice film in which a magnetic material and a nonmagnetic metal were laminated (Baibich et al., Phys. Rev. Lett. 61 (1988) pp. 2472 to 2475). Since then, research related to this phenomenon has been actively conducted.
[0003]
Recently, various applications using artificial lattice films exhibiting these giant magnetoresistances have been studied.For example, there is application research as a magnetic sensor or a recording element. What has been used (MRAM) has attracted attention.
[0004]
Also, a magnetoresistance effect has been found in a ferromagnetic tunnel junction in which magnetic layers are stacked via a tunnel insulating film.
For example, in a ferromagnetic tunnel junction using Fe and Al 2 O 3 , when the coercive forces of the Fe films on both sides are different, the magnetization of the Fe films on both sides changes from a parallel state to an anti-parallel state during the magnetization process. It has been shown that a magnetoresistance effect is caused by a change in tunnel resistance (Miyazaki et al., Journal of Magnetics and Magnetic Materials 139 (1995) L231-L234). In particular, this system has a large magnetoresistance effect of 20% or more even at room temperature.
[0005]
Also recently, according to Moodera et al. (Phys. Rev. Lett. 74 (1995) pp. 3273 to 3276), the method of forming a ferromagnetic tunnel junction of the combination of CoFe / Al2O3 / Co is improved by improving the method of forming the junction at room temperature. It is shown that a magnetic resistance of 10% or more can be obtained.
[0006]
As described above, a large magnetoresistance effect has also been obtained for ferromagnetic tunnel junctions, but there has been little application research on this, and there have been almost no applications for magnetic sensors and information storage devices. It has not been.
[0007]
[Problems to be solved by the invention]
As described above, the application of the ferromagnetic tunnel junction using the magnetoresistance effect, particularly the application as a recording element has not been studied.
The present invention has been made in consideration of the above points, and provides a novel magnetoresistive element and a magnetic information reading method capable of performing non-destructive or multi-value recording / reading using a ferromagnetic tunnel junction. With the goal.
[0008]
[Means for Solving the Problems]
The present invention includes a first ferromagnetic conductive layer, a second ferromagnetic conductive layer, a first tunnel insulating layer interposed between the first and second ferromagnetic conductive layer, the third strong a magnetic conductive layer, and a second tunnel insulating layer interposed between the second and third ferromagnetic conductive layer, first and respectively provided on the outer side of the first and third ferromagnetic conductive layer and a second antiferromagnetic layer, said coercive force of the second ferromagnetic conductive layer rather smaller than the coercive force of the first and third ferromagnetic conductive layer, the first to third The magneto-resistance effect element is characterized in that adjacent magnetization directions of the ferromagnetic conductive layers are substantially the same or opposite to each other . For example, the magnetization directions of the first and third ferromagnetic conductive layers are substantially the same as each other, and the magnetization directions of the second ferromagnetic conductive layer are the first and third ferromagnetic conductive layers. Are magnetoresistive elements whose directions of magnetization are substantially the same as or opposite to each other.
[0009]
The present invention also provides a first ferromagnetic conductive layer, a second ferromagnetic conductive layer, a first tunnel insulating layer interposed between the first and second ferromagnetic conductive layers, , A second tunnel insulating layer interposed between the second and third ferromagnetic conductive layers, and first and third ferromagnetic conductive layers provided outside the first and third ferromagnetic conductive layers, respectively. A first antiferromagnetic layer and a second antiferromagnetic layer, wherein the coercive force of the second ferromagnetic conductive layer is smaller than the coercive force of the first and third ferromagnetic conductive layers. A method for reading magnetic information of a magnetoresistive element, wherein the magnetization directions of adjacent layers of the ferromagnetic conductive layers are substantially the same or opposite to each other, wherein the magnetization direction of the second ferromagnetic conductive layer is Can be changed, and based on the tunnel current flowing through the first and second tunnel insulating layers, the first through third A magnetic information reading method characterized by reading the relative relationship of ferromagnetic conductive layers each of the magnetization directions as magnetic information. For example, the magnetization directions of the first and third ferromagnetic conductive layers are substantially the same as each other, and the magnetization directions of the second ferromagnetic conductive layer are the first and third ferromagnetic conductive layers. And the magnetization directions of the first and third ferromagnetic conductive layers and the magnetization direction of the second ferromagnetic conductive layer are substantially the same or opposite to each other. This is a magnetic information reading method for reading as magnetic information.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The principle of the present invention will be described with reference to FIG. The magnetic laminate (6) includes a first ferromagnetic conductive layer (1), a first tunnel insulating layer (2), a second ferromagnetic conductive layer (3), a second tunnel insulating layer (4), A structure in which the third ferromagnetic conductive layer (5) is sequentially laminated is adopted.
[0011]
Here, it is assumed that the coercive force of the second ferromagnetic conductive layer (3) is smaller than the coercive force of the first and third ferromagnetic conductive layers (1) and (5).
Magnetic recording is performed by magnetizing the first and third ferromagnetic conductive layers (1) and (5) in the same direction. In this figure, the upward magnetization state is “0” and the downward magnetization state is “1”.
[0012]
The direction of magnetization of the second ferromagnetic conductive layer (3) is undefined. However, the coercive force (H 2 ) of the second ferromagnetic conductive layer (3) is smaller than the coercive force (H 1 , H 3 ) of the first and third ferromagnetic conductive layers. That H 1, H 3> H> second ferromagnetic conductive layer located intermediate by applying a magnetization of H 2 (3) can be controlled magnetization direction only.
[0013]
First, reading of the state of “0” is performed.
It is assumed that the direction of magnetization of the second ferromagnetic conductive layer is controlled using the current magnetic field. That is, a conductor is provided close to the magnetic laminate, and a magnetic field is applied by passing a current through the conductor. It is assumed that the direction of magnetization is determined in the same direction as “0” when a positive pulse is applied and in the same direction as “1” when a negative pulse is applied.
[0014]
The direction of magnetization of the second ferromagnetic conductive layer before the input of the positive pulse is undefined, but is assumed to be the same direction as “0” for convenience. If necessary, a positive pulse may be applied to set the initial state to the direction of “0”. The reverse is also possible.
[0015]
When a positive pulse is applied, the magnetizations of the first, second, and third ferromagnetic conductive layers have the same direction, and a tunnel current easily flows through the magnetic laminate (6). On the other hand, when a negative pulse is applied, the magnetization directions of the first and second ferromagnetic conductive films are opposite, and the magnetization directions of the second and third ferromagnetic conductive films are opposite. Therefore, it becomes very difficult for a tunnel current to flow through the magnetic laminate.
[0016]
FIG. 1A shows the timing of the application of the positive and negative pulses, FIG. 1B shows the direction of the magnetization in the case of recording “0”, and FIG. 1C shows the magnitude of the tunnel current accordingly. Show. When a positive pulse is applied, a tunnel current flows, and when a negative pulse is applied, a tunnel current hardly flows. Although the positive pulse and the negative pulse are separated in this figure, they may be continuous.
[0017]
In the figure, the direction of magnetization of the second ferromagnetic conductive layer when there is no positive / negative pulse is to maintain the state of the pulse applied immediately before. There is also a possibility of inversion due to the influence of magnetostatic joining or the like. Therefore, it is sufficient to detect the tunnel current when the positive and negative pulses are applied. Needless to say, if the voltage detection is performed, the chart of FIG.
[0018]
In the case of "1", it is opposite to "0" (FIGS. 1 (d) and (e)), and the tunnel current changes from small to large.
In the case of "0" and "1", when the voltage generated at both ends of the magnetic laminate (6) when a positive pulse is applied is used as a reference, when the voltage rises (displacement of + ΔV) in the above-described example, 0 ", and when descending (-ΔV displacement), it can be determined as" 1 ". That is, "0" and "1" can be determined not by the absolute amount of the output but by the sign of the displacement, and reading with an excellent S / N ratio becomes possible.
[0019]
Further, in this case, nondestructive reading can be performed.
In FIG. 2, ternary data "0" (FIGS. 2B and 2C), "1" (FIGS. 2D and 2E), and "2" (FIGS. 2F and 2G) are reproduced. The case will be described.
[0020]
For example, when the magnetization directions of the first and third ferromagnetic conductive layers are upward, “0” is set, when they are downward, “2”, and when they are different, “1”. As in the example of FIG. 1, the magnetization direction of the second ferromagnetic conductive layer is initially set to the upward direction. FIG. 2A shows an example of a current pulse for generating an external magnetic field, and FIGS. 2A, 2E, and 2G are described with the same timing as in FIG.
[0021]
When a positive pulse is applied to make the magnetization of the second ferromagnetic conductive layer upward, when "0", the magnetizations of the first to third ferromagnetic conductive layers are aligned, so that a tunnel current flows easily, and the output is increased. In other cases, the voltage is low (V L ), and in other cases, the magnetization is not uniform, so that the tunnel current becomes difficult to flow, and the output voltage becomes high (V H ).
[0022]
Subsequently, when a negative pulse is applied, in the case of “2”, the magnetization becomes VL in which the magnetization is uniform downward, but in other cases, it becomes VH .
Therefore, determination if the addition of positive and negative pulse, when the V L → V H is "0", if the V H → V H "1" , if the V H → V L "2" it can.
[0023]
In this way, multi-value recording is also possible. Moreover, the spin directions of the first and third ferromagnetic conductive layers do not change before and after reading, and non-destructive reading can be performed.
Third, quaternary data “0” (FIGS. 3 (b) and (c)), “1” (FIGS. 3 (d) and (e)), “2” (FIGS. 3 (f) and (g)), and “3” The case of reproducing “(FIG. 3 (h) (i))” will be described.
[0024]
For example, when the magnetization directions of the first and third ferromagnetic conductive layers are upward, “0” is set, when the magnetization directions are downward, “3”, and when they are different, “1” is set when the magnetization of the first ferromagnetic layer is upward. "Downward is defined as" 2 ".
[0025]
As in the example of FIG. 1, the magnetization direction of the second ferromagnetic conductive layer is initially set to the upward direction. FIG. 3A shows an example of a current pulse for generating an external magnetic field, and FIGS. 3A, 3E, 3G, and 3I are described with the same timing as in FIG.
[0026]
In addition, in the case of FIGS. 1 and 2, H 1 , H 3 > H (read)> H 2 , but the relationship of H 1 > H 3 is further added. Further, small and large amplitudes are prepared for reading, and H 1 > H (large)> H 3 > H (small)> H 2 .
[0027]
When a positive pulse (small amplitude) is applied to make the magnetization of the second ferromagnetic conductive layer upward, a tunnel current flows when the value is “0” because the magnetizations of the first to third ferromagnetic conductive layers are aligned. In other cases, the output voltage is low (V L ), and in other cases, since the magnetization is not uniform, the tunnel current is difficult to flow, and the output voltage is high (V H ).
[0028]
Subsequently, when a negative pulse is applied, in the case of "4", the magnetization becomes VL in which the magnetization is uniform downward, but the others become VH .
Further, when a positive pulse (large) is applied, the third ferromagnetic layer is directed upward regardless of the recording state, so that the voltage becomes VH except for "2" and "3".
[0029]
Therefore, positive (small) negative-positive cases plus pulse (large), if the V L → V H → V L "0", if the V H → V H → V L "1", The case where VH → VH → VH becomes “2” and the case where VH → VL → VH becomes “3” can be determined.
[0030]
Although destructive reading is thus performed, four-level recording is also possible.
The device of the present invention is produced, for example, as follows.
A ferromagnetic material such as Fe, Co, or Ni, a magnetic alloy such as Permalloy, or a semimetal such as a Heusler alloy is used for the ferromagnetic layer, and an oxide such as NiO or Al 2 O 3 is used for the insulating layer. Can be. Here, the thickness of the ferromagnetic layer is preferably 1 nm to 500 nm, and the thickness of the insulating layer is preferably 1 nm to 40 nm.
[0031]
The method of forming the junction will be described below in the case where Fe is used as the ferromagnetic layer and Al 2 O 3 is used as the insulator layer.
A ferromagnetic tunnel junction is created on a glass substrate. The ferromagnetic layer is formed by an ion beam sputtering method. At this time, after the inside of the chamber is evacuated to 1 × 10 −6 Torr or less, Ar is introduced at 1 × 10 −4 Torr, and the film is formed at an acceleration voltage of Ar ions of 600 V. The first and third ferromagnetic layers have a thickness of 100 nm, the second ferromagnetic layer has a thickness of 50 nm, and the coercive force of the second ferromagnetic layer is equal to that of the first and third ferromagnetic layers. It was made smaller than the coercive force. The insulator layer is formed by forming Al to a thickness of 5 nm to 25 nm by an ion beam sputtering method, and is naturally oxidized in the air for 24 hours to form Al 2 O 3 .
[0032]
The method of forming the junction will be described below in the case where Fe is used as the ferromagnetic layer and Al 2 O 3 is used as the insulator layer. A ferromagnetic tunnel junction is created on a glass substrate. The ferromagnetic layer is formed by an ion beam sputtering method. At this time, after the inside of the chamber is evacuated to 1 × 10 −6 Torr or less, Ar is introduced at 1 × 10 −4 Torr, and an acceleration voltage of Ar ions is set to 600 V to form a film. The first and third ferromagnetic layers have a thickness of 100 nm, the second ferromagnetic layer has a thickness of 50 nm, and the coercive force of the second ferromagnetic layer is equal to that of the first and third ferromagnetic layers. It was made smaller than the coercive force. The insulator layer is formed by forming Al to a thickness of 5 nm to 25 nm by an ion beam sputtering method, and is naturally oxidized in the air for 24 hours to form Al 2 O 3 .
[0033]
The theoretical analysis of a ferromagnetic tunnel junction composed of two types of ferromagnetic layers separated by one insulator has been performed by Slonczewski (Phys. Rev. B39 (1989) pp. 6995 to 7002). According to this, the tunnel conductance (G) is proportional to the transmission coefficient of the junction in the limit where the insulator is infinitely thick.
[0034]
That is, G is proportional to (1 + εcos θ). θ represents the angle between the magnetizations of the two ferromagnetic layers, ε is a substance-dependent constant, and takes a value of 0 <ε ≦ 1. Therefore, the conductance takes the maximum value when the magnetization of the ferromagnetic layer is parallel (θ = 0), and takes the minimum value when the magnetization of the ferromagnetic layer is antiparallel (θ = π). When a semimetal such as a Heusler alloy is used, ε = 1.
[0035]
In the present invention, three ferromagnetic layers are included, which is a combination of two tunnel junctions. The overall transmission coefficient can be represented by the transmission coefficient of each tunnel junction. In particular, when the transmission coefficient T of each tunnel junction is small, the total of T is proportional to T 2 .
[0036]
Therefore, the tunnel conductance (G total ) is proportional to (1 + εcos θ) 2 .
Therefore, it can be seen that having three magnetic layers increases the differential coefficient of the conductance with respect to the magnetic field. FIG. 4 shows the proportionality coefficient normalized when ε = 1. Therefore, it is easy to detect a change in the tunnel current with respect to a change in the magnetic field, which is suitable for a magnetic sensor.
[0037]
Further, an antiferromagnetic layer such as FeMn is provided on the outside to reduce the influence of an external magnetic field on the magnetization of the first and third ferromagnetic layers, and the first and third ferromagnetic layers are interacted with these layers. It is also conceivable to fix the magnetization of the ferromagnetic layer.
[0038]
【The invention's effect】
As described above, according to the present invention, a novel magnetoresistance effect element using a ferromagnetic tunnel junction can be obtained, and a magnetic recording system capable of multi-valued or non-destructive reading can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of the present invention.
FIG. 2 is a schematic diagram of the present invention.
FIG. 3 is a schematic diagram of the present invention.
FIG. 4 is a characteristic diagram of the present invention.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06958196A JP3585629B2 (en) | 1996-03-26 | 1996-03-26 | Magnetoresistive element and magnetic information reading method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06958196A JP3585629B2 (en) | 1996-03-26 | 1996-03-26 | Magnetoresistive element and magnetic information reading method |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2004198732A Division JP4346517B2 (en) | 2004-07-06 | 2004-07-06 | Magnetoresistive effect element and information storage element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09260743A JPH09260743A (en) | 1997-10-03 |
| JP3585629B2 true JP3585629B2 (en) | 2004-11-04 |
Family
ID=13406931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06958196A Expired - Fee Related JP3585629B2 (en) | 1996-03-26 | 1996-03-26 | Magnetoresistive element and magnetic information reading method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3585629B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10418101B1 (en) | 2018-03-20 | 2019-09-17 | Toshiba Memory Corporation | Semiconductor memory device and method of controlling the same |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6611405B1 (en) | 1999-09-16 | 2003-08-26 | Kabushiki Kaisha Toshiba | Magnetoresistive element and magnetic memory device |
| US6469926B1 (en) * | 2000-03-22 | 2002-10-22 | Motorola, Inc. | Magnetic element with an improved magnetoresistance ratio and fabricating method thereof |
| JP2002246567A (en) | 2001-02-14 | 2002-08-30 | Toshiba Corp | Magnetic random access memory |
| JP3576111B2 (en) | 2001-03-12 | 2004-10-13 | 株式会社東芝 | Magnetoresistance effect element |
| US6590803B2 (en) | 2001-03-27 | 2003-07-08 | Kabushiki Kaisha Toshiba | Magnetic memory device |
| US6593608B1 (en) * | 2002-03-15 | 2003-07-15 | Hewlett-Packard Development Company, L.P. | Magneto resistive storage device having double tunnel junction |
| JP5540180B2 (en) * | 2007-12-14 | 2014-07-02 | 国立大学法人東北大学 | Magnetic field detection element and magnetic field detection device |
| WO2010041719A1 (en) * | 2008-10-10 | 2010-04-15 | 株式会社アルバック | Storage element |
| JP6069705B2 (en) * | 2013-05-20 | 2017-02-01 | 富士通株式会社 | Memory device |
-
1996
- 1996-03-26 JP JP06958196A patent/JP3585629B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10418101B1 (en) | 2018-03-20 | 2019-09-17 | Toshiba Memory Corporation | Semiconductor memory device and method of controlling the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09260743A (en) | 1997-10-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Daughton | Magnetoresistive memory technology | |
| Grünberg | Layered magnetic structures: History, highlights, applications | |
| US4949039A (en) | Magnetic field sensor with ferromagnetic thin layers having magnetically antiparallel polarized components | |
| KR100344030B1 (en) | Magnetic element, magnetic memory device, magnetoresistance effect head, and magnetic storage system | |
| JP2001195878A (en) | Magnetic resistance effective memory, reproducing method for information stored in the memory, and its reproducing device | |
| KR20050083957A (en) | Spin-injection device and magnetic device using spin-injection device | |
| JPH09139068A (en) | Information recording/reproducing method and information storage | |
| JP3556457B2 (en) | Spin-dependent conductive element and electronic and magnetic components using the same | |
| JPH1041132A (en) | Magnetic resistance effect film | |
| JP3585629B2 (en) | Magnetoresistive element and magnetic information reading method | |
| JP3691898B2 (en) | Magnetoresistive effect element, magnetic information reading method, and recording element | |
| JP2001156358A (en) | Magneto-resistance effect element and magnetic memory element | |
| US20010022373A1 (en) | Magnetic memory element and magnetic memory using the same | |
| JP3547974B2 (en) | Magnetic element, magnetic head and magnetic storage device using the same | |
| US5773156A (en) | Magnetoresistance effect element | |
| JP3455055B2 (en) | Magnetic element, magnetic head and magnetic storage device using the same | |
| JP3593463B2 (en) | Ferromagnetic tunnel effect element and magnetic device using the same | |
| JPH113585A (en) | Magnetic thin film memory element and its recording and reproducing method | |
| JP4346517B2 (en) | Magnetoresistive effect element and information storage element | |
| JP4136028B2 (en) | Magnetic thin film memory element, magnetic thin film memory using the same, and recording / reproducing method thereof | |
| JP3677107B2 (en) | Magnetoresistive effect element | |
| JP3350311B2 (en) | Magnetic thin film memory element and magnetic thin film memory | |
| JP2003197872A (en) | Memory using magneto-resistance effect film | |
| Zheng et al. | 3-D FEM micromagnetic modeling of spin-valve sensors | |
| Hathaway et al. | Resource letter STMN-1: Spin transport in magnetic nanostructures |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20040427 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20040507 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20040706 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20040730 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20040804 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20070813 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080813 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090813 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090813 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100813 Year of fee payment: 6 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100813 Year of fee payment: 6 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110813 Year of fee payment: 7 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110813 Year of fee payment: 7 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120813 Year of fee payment: 8 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120813 Year of fee payment: 8 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130813 Year of fee payment: 9 |
|
| LAPS | Cancellation because of no payment of annual fees |