Field-Free Perpendicular Magnetization Switching Through Topological Surface State in Type-II Dirac Semimetal Pt₃Sn

Spin-orbit torque (SOT) induced by current is a promising approach for electrical manipulation of magnetization in advancing next-generation memory and logic technologies. Conventional SOT-driven perpendicular magnetization switching typically requires an external magnetic field for symmetry breaking, limiting practical applications. Recent research has focused on achieving field-free switching through out-of-plane SOT, with the key challenge being the exploration of new spin source materials that can generate z-polarized spins with high charge-to-spin conversion efficiency, structural simplicity, and scalability for large-scale production. This study demonstrates field-free perpendicular switching using an ultrathin type-II Dirac semimetal Pt₃Sn layer with a topological surface state. Density functional theory calculations reveal that the unconventional SOT originates from a spin texture with C_3v symmetry, leading to significant z-polarized spin accumulation in the Pt₃Sn (111) surface, enabling the deterministic switching of perpendicular magnetization. These results highlight the potential of Dirac semimetals like Pt₃Sn as scalable and efficient spin sources, facilitating the development of low-power, high-density spintronic memory and logic devices.