State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China.
College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing, 100049, China.
Nat Commun. 2023 Mar 30;14(1):1778. doi: 10.1038/s41467-023-37506-9.
Spin-orbit torques (SOTs) have been widely understood as an interfacial transfer of spin that is independent of the bulk properties of the magnetic layer. Here, we report that SOTs acting on ferrimagnetic FeTb layers decrease and vanish upon approaching the magnetic compensation point because the rate of spin transfer to the magnetization becomes much slower than the rate of spin relaxation into the crystal lattice due to spin-orbit scattering. These results indicate that the relative rates of competing spin relaxation processes within magnetic layers play a critical role in determining the strength of SOTs, which provides a unified understanding for the diverse and even seemingly puzzling SOT phenomena in ferromagnetic and compensated systems. Our work indicates that spin-orbit scattering within the magnet should be minimized for efficient SOT devices. We also find that the interfacial spin-mixing conductance of interfaces of ferrimagnetic alloys (such as FeTb) is as large as that of 3d ferromagnets and insensitive to the degree of magnetic compensation.
自旋轨道扭矩（SOT）被广泛理解为一种界面自旋转移，与磁性层的体性质无关。在这里，我们报告说，作用在亚铁磁 FeTb 层上的 SOT 在接近磁补偿点时会减小并消失，因为由于自旋轨道散射，自旋转移到磁化强度的速率比自旋弛豫到晶格的速率慢得多。这些结果表明，磁性层内竞争自旋弛豫过程的相对速率在确定 SOT 的强度方面起着关键作用，这为铁磁体和补偿系统中各种甚至看似令人困惑的 SOT 现象提供了统一的理解。我们的工作表明，为了实现高效的 SOT 器件，应该最小化磁体内的自旋轨道散射。我们还发现，亚铁磁合金（如 FeTb）界面的界面自旋混合电导与 3d 铁磁体一样大，并且不受磁补偿程度的影响。
