| Project/Area Number |
16K14228
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| Research Category |
Grant-in-Aid for Challenging Exploratory Research
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| Allocation Type | Multi-year Fund |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
PHAM NAM HAI 東京工業大学, 工学院, 准教授 (50571717)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
Fiscal Year 2018: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2017: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2016: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
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| Keywords | SOT-MRAM / トポロジカル絶縁体 / スピン軌道トルク / スピンホール効果 / MRAM |
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| Outline of Final Research Achievements |
In this research, we developed a high-performance pure spin current source using BiSb topological insulator thin films for the next generation spin-orbit torque (SOT) MRAM. We developed growth techniques for high quality BiSb thin films with both high electrical conductivity and high spin Hall angle. We found that BiSb(012) thin films have a giant spin Hall angle of 52 at room temperature. We further demonstrated current-induced magnetization switching of a MnGa ferromagnetic thin film with a current density as low as 1.5 MA/square cm. This value is one to two orders of magnitudes lower than those of heavy metal/MnGa bilayers. Furthermore, the spin Hall conductivity of BiSb is 30 times higher than that of Pt, and 100 times higher than that of other topological insulators, such as Bi2Se3. Our results show that BiSb is very promising for SOT-MRAM.
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| Academic Significance and Societal Importance of the Research Achievements |
スピン軌道トルク磁気抵抗メモリ(SOT-MRAM)は、スピンホール効果による純スピン流を用いて、高速で書き込みができる次世代の不揮発メモリ技術である。しかし、従来から純スピン流源として使われている重金属は、スピンホール角が低い。本研究では、BiSbトポロジカル絶縁体薄膜を評価したところ、金属並みの高い電気伝導率と超巨大なスピンホール角を示すことを発見した。さらにBiSbを用いて、従来よりも1桁～2桁少ない電流密度でMnGa垂直磁性膜の磁化反転を実証した。BiSbをSOT-MRAMへ応用すると、書き込み電流を1桁、エネルギーを2桁低減でき、さらに記録速度を20倍、記録密度を1桁向上させられる。
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