Deterministic Field-Free Switching of Perpendicular Magnetization by Bulk Mirror Symmetry Broken Bi_{1- x}Sb_x (012) with...

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 $\sim 1.12\times {10}^5\frac{\hslash }{2e}{\Omega }^{-1}{m}^{-1}$ (for x = 0.2), which is 5.6 times larger than that of TaIrTe₄. Our results establish bulk mirror-symmetry engineering as an effective strategy for designing energy-efficient field-free spin-orbit torque devices.