Deterministic Field‐Free Switching of Perpendicular Magnetization by Bulk Mirror Symmetry Broken Bi 1− x Sb x (012) with High Spin Hall Conductivity

ABSTRACT Out‐of‐plane spin–orbit torque generation in mirror‐symmetry‐broken materials is a promising approach for current‐induced field‐free magnetization switching. However, the key challenge lies in identifying materials with high in‐plane spin Hall conductivity that simultaneously generate large out‐of‐plane spin–orbit torque for low‐power spintronic applications. Previously studied low‐symmetry materials, in which mirror‐symmetry breaking is confined to the surface and the spin Hall conductivity is low, have not resolved this challenge. Here, we demonstrate deterministic field‐free magnetization switching enabled by the bulk‐mirror‐symmetry‐broken topological material Bi 1− x Sb x (012) with high in‐plane spin Hall conductivity. The power consumption is two orders of magnitude lower than that of heavy‐metal‐based devices. Spin‐torque ferromagnetic resonance measurements confirm the bulk origin of the out‐of‐plane spin–orbit torque in Bi 1− x Sb x (012), yielding an out‐of‐plane spin Hall conductivity of (for x = 0.2), which is 5.6 times larger than that of TaIrTe 4 . Our results establish bulk mirror‐symmetry engineering as an effective strategy for designing energy‐efficient field‐free spin–orbit torque devices.