Enhancement of spin orbit torque by introducing the broken inversion symmetry and development of 3-dimensional magenetic memory

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02182
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: Nagoya University
• Principal Investigator: Kato Takeshi 名古屋大学, 未来材料・システム研究所, 教授 (50303665)
• Co-Investigator(Kenkyū-buntansha): 大島 大輝 名古屋大学, 工学研究科, 助教 (60736528)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 電子・電気材料 / 磁性材料 / スピントロニクス

Outline of Final Research Achievements

Spin Orbit Torque (SOT) switching is considered as a promising way of the next generation writing scheme of the magnetic random access memories. This study focused on the relationship between SOT switching current density and structural inversion symmetry of the magnetic materials, and Gd/FeCo multilayers with graded layered thickness and Tb/Gd/FeCo multilayers were investigated. The SOT switching current density of Gd/FeCo multilayers decreased with increasing the gradient of the layer thickness of the multilayer. Moreover, in Tb/Gd/FeCo multilayers, the SOT switching current density decreased with increasing Tb layer thickness, even though the effective perpendicular anisotropy increased. These results suggest the increase of the broken inversion symmetry along film normal direction decreases the SOT switching current density.

Free Research Field

磁性薄膜工学

Academic Significance and Societal Importance of the Research Achievements

スピン軌道トルク（Spin orbit torque: SOT）は，Society 5.0を支える大容量磁気ランダムアクセスメモリ（MRAM）の新規磁化反転手法として期待されているが，磁化反転の臨界電流密度の低減が求められている．本研究ではメモリの機能を果たす磁性膜に膜厚方向の空間反転対称性の破れを人工的に導入し，この空間対称性の破れがスピン軌道トルク磁化反転の臨界電流密度を低減する可能性があることを示した．磁性膜の空間反転対称性の破れとスピン軌道トルクとの相関は未解明な部分も多く，今後も継続的に研究を進め，MRAMの飛躍的高密度化，低消費電力化を可能とする技術を探求する必要がある．