Investigation of sub-configurations reveals stable spin-orbit torque switching polarity in polycrystalline Mn₃Sn

Previous studies have demonstrated the switching of the octupole moment in Mn₃Sn driven by spin-orbit torque (SOT). However, they did not account for the polycrystalline nature of the sample when explaining the switching mechanism. In this work, we use samples with various atomic orientations to capture this polycrystalline nature. The samples are classified into three different configurations based on the relative alignment between the Kagome plane, the spin polarization, and the external magnetic field. We thoroughly investigate their SOT-induced spin dynamics and demonstrate that different configurations lead to distinct outcomes. Our findings reveal that the configuration where the Kagome plane is perpendicular to the spin polarization exhibits robust switching with stable polarity, whereas the signals from the configuration where the Kagome plane is parallel to the spin polarization will cancel each other out. By comparing our findings with experimental results, we pinpoint the primary sources contributing to the measured anomalous Hall effect signals. Additionally, we establish a dynamic balance model that incorporates the unique properties of Mn₃Sn to elucidate these observations. Our study highlights the essential role of the polycrystalline nature in understanding SOT switching. By clarifying the underlying physical mechanisms, our work resolves the long-standing puzzle regarding the robust SOT switching observed in Mn₃Sn.