Enhancement of the Unconventional Spin–Orbit Torque Efficiency through Kagome Orientation Engineering in Epitaxial Noncollinear Antiferromagnet Mn 3 Sn

Noncollinear antiferromagnets show great potential for next-generation spintronic devices due to their unique spin textures and ultrafast dynamics, with Kagome-lattice Mn 3 Sn 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 Mn 3 Sn, confirming z -direction polarized spin current and unconventional spin polarization in the material. Strikingly, (112̅0)-oriented Mn 3 Sn films exhibit 13-fold higher unconventional SOT efficiency ξ z 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 Mn 3 Sn as a versatile platform for energy-efficient antiferromagnetic spintronic devices.