Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co₂MnGa

Abstract

Spin-orbit torque (SOT) is receiving tremendous attention from both fundamental and application-oriented aspects. Co2MnGa, a Weyl ferromagnet that is in a class of topological quantum materials, possesses cubic-based high structural symmetry, the L21 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 Co2MnGa. The magnitude of the SOT is comparable to that of heavy metal/ferromagnet bilayer systems, despite the high inversion symmetry of the Co2MnGa 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.

Current-Induced Magnetization Switching Behavior in Perpendicular Magnetized L10-MnAl/B2-CoGa Bilayer

“…By integrating the known SOT efficiencies of CoGa (𝑡CoGa = 5 nm, 𝜉DL = 0.042) and Co2MnGa (𝑡Co 2 MnGa = 10 nm, 𝜉DL = −0.052), [54] we have estimated the SOT efficiency of 1.5nm-thick Co2MnGa as −0.006, assuming 𝜆s to be 3 nm. [55] For the 3-nm-thick CoGa layer, the efficiency has been determined to be 0.023. Moreover, theoretical studies have demonstrated that 𝜎𝑧 can be generated in the IMA layer when the direction of the applied current is parallel to its magnetic moment.…”