Aoki Motomi, Yin Yuefeng, Granville Simon, Zhang Yao, Medhekar Nikhil V, Leiva Livio, Ohshima Ryo, Ando Yuichiro, Shiraishi Masashi
Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto 615-8510, Japan.
Center for Spintronics Research Network, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-011, Japan.
Nano Lett. 2023 Aug 9;23(15):6951-6957. doi: 10.1021/acs.nanolett.3c01573. Epub 2023 Jul 21.
Spin-orbit torque (SOT) is receiving tremendous attention from both fundamental and application-oriented aspects. CoMnGa, a Weyl ferromagnet that is in a class of topological quantum materials, possesses cubic-based high structural symmetry, the L2 crystal ordering, which should be incapable of hosting anisotropic SOT in conventional understanding. Here we show the discovery of a gigantic anisotropy of self-induced SOT in CoMnGa. The magnitude of the SOT is comparable to that of heavy metal/ferromagnet bilayer systems, despite the high inversion symmetry of the CoMnGa structure. More surprisingly, a sign inversion of the self-induced SOT is observed for different crystal axes. This finding stems from the interplay of the topological nature of the electronic states and their strong modulation by external strain. Our research enriches the understanding of the physics of self-induced SOT and demonstrates a versatile method for tuning SOT efficiencies in a wide range of materials for topological and spintronic devices.
自旋轨道扭矩（SOT）在基础研究和应用研究方面都受到了极大的关注。CoMnGa是一种属于拓扑量子材料类别的外尔铁磁体，具有基于立方的高结构对称性，即L2晶体有序性，按照传统理解，它应该无法承载各向异性的SOT。在此，我们展示了在CoMnGa中发现的巨大的自感应SOT各向异性。尽管CoMnGa结构具有高反演对称性，但其SOT的大小与重金属/铁磁体双层系统相当。更令人惊讶的是，对于不同的晶轴，观察到了自感应SOT的符号反转。这一发现源于电子态的拓扑性质及其受外部应变的强烈调制之间的相互作用。我们的研究丰富了对自感应SOT物理机制的理解，并展示了一种在拓扑和自旋电子器件的广泛材料中调节SOT效率的通用方法。
