成果報告書詳細
管理番号20090000000120
タイトル*平成20年度中間年報 平成20年度スピントロニクス不揮発性機能技術プロジェクト2
公開日2009/9/17
報告書年度2008 - 2008
委託先名国立大学法人東北大学
プロジェクト番号P06016
部署名電子・情報技術開発部
和文要約以下本編抜粋:1. 研究開発の内容及び成果等 超高集積で高速な不揮発性メモリとして期待されるスピンRAM のための基盤技術を開発する為に、東北大学では、1.記憶層材料の探索・TMR 素子構造の最適化、および、2.スピン注入磁化反転ダイナミクスの研究を行なった。また、トランジスタへの不揮発性機能の付与を目指して、3.ハーフメタル電極方式のスピントランジスタの開発研究を行った。平成20年度の成果を以下の通りまとめた。いずれの研究テーマについても、当初の研究計画どおりに進展が見られ、次年度以降に更に研究を進めることで、最終目標の実現が可能であると考えられる。
英文要約Report of research and development and results In order to develop fundamental technologies for spin-RAM which is expected to be Gbit and very fast non-volatile memory, we have carried out the following research: 1. Search for memory layer materials and optimization of TMR device stacking structure 2. Investigation of spin injection magnetization switching. And also, in order to realize non-volatile transistor, we performed: 3. Development of Spin transistor with Half-metal electrodes.  These researches and developments were in progress as we planed originally, and we consider our aims of this project can be achieved by further researches planed in next year. We summarized the results obtained in 2008 as follows. 1. Search for memory layer materials and optimization of TMR device stacking structure In order to optimize TMR device stacking structure, magnetic property for CoNiPt alloys, which has large crystalline magnetic anisotropy, are investigated systematically and we examined if CoNiPt alloys are candidate of reference layer material for TMR devices. We have succeeded to reduce the thickness of CoNiPt alloy down to 2.6 nm. For CoPt alloy with addition of 37.5% Ni, ferromagnetic transition temperature (Tc) was quite low and around 120℃. 2. Investigation of spin injection magnetization switching By using an angular variation measurement of ferromagnetic resonance, which has beendeveloped in last year, we clarified magnetic damping constant for several materials with high magnetic anisotropy, which supported to enhance performance of the memory layer material. In addition, we have developed angular and field variation measurement of optical pump-probe method and we have succeeded to evaluate magnetic damping constant for various materials which have been developed by Tohoku Univ., AIST, and Toshiba and had large magnetic anisotropy constant of 2-20 Merg/cc. 3. Development of Spin transistor with Half-metal electrodes.  Research aims in the plan of this year are as follows; Development of half-metal materials which has spin polarization close to unity, Fabrication of prototype spin transistor device, Investigation of switching property induced by on/off gate voltage, and clarifying subject for realizing spin transistor using half-metals. To increase spin polarization of Co2MnSi Heusler alloys which has been developed till the end of last year, Fe element was substituted into Mn site in Co2MnSi. We succeeded to obtain TMR ratio of 170% in Co2Fe0.4Mn0.6Si/Al-oxide/CoFe magnetic tunnel junction (MTJ) at low temperature. Spin polarization of Co2Fe0.4Mn0.6Si was evaluated to be 92% from TMR ratio, which is the highest value of those obtained in the other Heusler alloys developed until now and corresponds to TMR ratio of 1100% as Co2Fe0.4Mn0.6Si is used for both electrodes in MTJs. We fabricated prototype devices of spin transistor and evaluated device performances. The devises exhibited the on/off current ratio of 320% by changing magnetizations alignment.
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