Microscopic origin of spin-orbit torque in ferromagnetic heterostructures: A first-principles approach
Microscopic origin of spin-orbit torque in ferromagnetic heterostructures: A first-principles approach
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DOI：
10.1103/physrevb.101.060405
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发表时间：
2020-02
影响因子：
3.7
通讯作者：
F. Mahfouzi;Rahul Mishra;Po-Hao Chang;Hyunsoo Yang;N. Kioussis
中科院分区：
文献类型：
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作者：
F. Mahfouzi;Rahul Mishra;Po-Hao Chang;Hyunsoo Yang;N. Kioussis
我们提出了一个基于从头计算的理论框架，阐明了正常金属（NM）/铁磁体（FM）异质结构中的自旋轨道矩（SOT）的起源。SOT被分解为两个贡献，即自旋霍尔和自旋轨道组件。我们发现（i）类场（FL）SOT主要由自旋轨道分量决定;（ii）在厚Pt膜的限制下，这两个分量对类阻尼（DL）力矩的贡献大小相当。自旋-轨道分量对DL-SOT的贡献仅存在于具有强SOC耦合强度的NM中。我们证明了FL-SOT可以用非平衡自旋分辨轨道矩积累来表示。计算结果表明，Pt/Co双层膜中氧诱导的FL-SOT符号反转是由于界面NM原子上的多数自旋轨道矩积累显著减少所致.
We present an ab initio based theoretical framework which elucidates the origin of the spin-orbit torque (SOT) in normal-metal (NM)/ferromagnet (FM) heterostructures. The SOT is decomposed into two contributions, namely, spin-Hall and the spin-orbital components. We find that (i) the fieldlike (FL) SOT is dominated by the spin-orbital component and (ii) both components contribute to the dampinglike (DL) torque with comparable magnitude in the limit of thick Pt film. The contribution of the spin-orbital component to the DL-SOT is present only for NMs with strong SOC coupling strength. We demonstrate that the FL-SOT can be expressed in terms of the nonequilibrium spin-resolved orbital moment accumulation. The calculations reveal that the experimentally reported oxygen-induced sign reversal of the FL-SOT in Pt/Co bilayers is due to the significant reduction of the majority-spin orbital moment accumulation on the interfacial NM atoms.