Enhancement of the Unconventional Spin-Orbit Torque Efficiency through Kagome Orientation Engineering in Epitaxial Noncollinear Antiferromagnet Mn3Sn.

Noncollinear antiferromagnets show great potential for next-generation spintronic devices due to their unique spin textures and ultrafast dynamics, with Kagome-lattice Mn3Sn a key spin-orbit torque (SOT) candidate enabled by room-temperature unconventional spin polarization. However, the impact of crystal orientation on its SOT efficiency remains unaddressed. Herein, we combine experiments and first-principles calculations to investigate Kagome-facet-dependent unconventional out-of-plane SOT in Mn3Sn, confirming z-direction polarized spin current and unconventional spin polarization in the material. Strikingly, (112̅0)-oriented Mn3Sn films exhibit 13-fold higher unconventional SOT efficiency ξz associated with z-direction spin polarization than (0002)-oriented counterparts, a behavior governed by Kagome lattice symmetry and facet-dependent spin transport. First-principles calculations further verify the Kagome plane's critical role in enhancing anisotropic spin textures and transport properties. This crystal-facet engineering strategy resolves the longstanding ambiguity in SOT anisotropy of noncollinear antiferromagnets and establishes Mn3Sn as a versatile platform for energy-efficient antiferromagnetic spintronic devices.