| Project/Area Number |
18360143
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Hokkaido University |
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Principal Investigator |
YAMAMOTO Masafumi Hokkaido University, Graduate School of Information Science and Technology, Professor. (10322835)
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| Co-Investigator(Kenkyū-buntansha) |
UEMURA Tetsuya Hokkaido University, Graduate School of Information Science and Technology, Associate Prof. (20344476)
MATSUDA Ken-ichi Hokkaido Univ, Graduate School of Information Science and Techonlogy, Assistant Prof. (80360931)
SAITO Toshiaki Toho University, Faculty of Science, Department of Physics, Professor (80170512)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥16,650,000 (Direct Cost: ¥14,700,000、Indirect Cost: ¥1,950,000)
Fiscal Year 2007: ¥8,450,000 (Direct Cost: ¥6,500,000、Indirect Cost: ¥1,950,000)
Fiscal Year 2006: ¥8,200,000 (Direct Cost: ¥8,200,000)
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| Keywords | half-metallic ferromagnets / Heusler alloy / ferromagnetic tunnel junctions / tunnel magnetoresistnce / spintonics / スピントロニクス / ホイスラー合金薄膜 |
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| Research Abstract |
The purpose of the present study was to develop spintronic devices utilizing the half-metallicity of Co-based Heusler alloys (Co_2YZ). Fully epitaxial magnetic tunnel junctions (MTJs) with a Co_2YZ thin film or Co_2YZ thin films and a MgO barrier featuring abrupt and extremely smooth interfaces were fabricated. Furthermore, high tunnel magnetoresistance (TMR) ratios were demonstrated at room temperature (RT) for fabricated Co_2YZ/MgO-based MTJs. The main results are summarized as follows.
1) The Heusler alloy-based MTJ device technology was developed. This device technology features the followings: a) all layers in the MTJ trilayer structures are epitaxial and single-crystalline, b) abrupt and atomically flat interfaces between a Co_2YZ (Co_2Cr_<0.6>Fe_<0.4>Al (CCFA), Co_2MnSi (CMS), or Co_2MnGe) thin film and a MgO tunnel barrier, and c) the interface region of CMS thin films underneath a MgO barrier is not oxidized.
2) The fabricated CCFA/MgO/Co_<50>Fe_<50> MTJs demonstrated a high TMR ratio of 109 % at RT (317% at 4.2 K).
3) Fully epitaxial exchange-biased MTJs with CMS thin films as both lower and upper electrodes and with a MgO barrier were fabricated.
The TMR ratios at both RT and 4.2 K increased with increasing the in-situ annealing temperature (T_a) just after the deposition of the upper CMS electrode. Furthermore, a high TMR ratio of 179% at RT (683% at 4.2 K) was demonstrated.
In summary, it was demonstrated that epitaxial, single-crystalline heterostructures consisting of Co_2YZ thin films and a MgO barrier are highly promising for spintronic devices that utilize the half-metallicity of Co-based Heusler alloys.
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