Clarifying physical mechanism of a very fast current-induced domain wall motion at low current density in RE-TM nanowire attributed to spin orbital torque.

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K14128
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Toyota Technological Institute
• Principal Investigator: Van Thach Pham 豊田工業大学, 工学(系)研究科(研究院), ポストドクトラル研究員 (70807809)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Keywords: スピン軌道トルク / 磁性細線メモリ / ジャロシンスキー守谷相互作用 / 磁壁駆動速度 / 希土類・遷移金属合金 / フェリ磁性材料 / 電流磁壁駆動 / 臨界電流密度

Outline of Final Research Achievements

IBM's Parkin et al. succeeded to inprove the domain wall velocity of 750m/sec using a complicated three-layer structure of ferromagnet/nonmagnetic material/ferromagnetic magnetic wire. The important key point is that the two magnetic layers are antiferromagnetically coupled. On the other hand, the GdFeCo single layer film is a ferrimagnetic material, and it is considered that the single GdFeCo layer is similar to antiferromagnetic material. Therefore, I prepared a GdFeCo/Pt heterointerface magnetic wire and investigated whether the domain wall motion velocity is improved. When the current pulse width was set to 100 nsec, the domain wall speed increased to 600 m/sec, approaching the IBM value. It was confirmed that the domain wall speed was improved to 2600 m/sec by using shortening the pulse width to 3 nsec (half-value width 6 nsec). Thus, ferrimagnetic wires are attractive because they have a simpler structure and can improve the domain wall speed.

Free Research Field

スピントロニクス

Academic Significance and Societal Importance of the Research Achievements

磁性細線メモリにとって重要な電流駆動磁壁移動速度を2600m/secに高めることに成功した。これはパルス半値幅6nsecでの値であるが、実際には設定値の3nsecでの駆動と考えると、磁壁移動速度は倍の5200m/secになる。この速度は驚異的で、このような早さを制御できる電子回路が無いので有効活用できないが、電子回路の進展具合では超高速低消費電力磁性細線メモリの実用化が期待できる結果である。また、パルス幅を100nsecから3nsecに変えると、駆動電力は2.5倍増えたが、磁壁移動速度は4倍に増えた。磁壁移動速度/駆動電力比をおよそ倍にすることができた。これも省電力化に貢献できる結果である。