Deterministic Field-Free Switching of Perpendicular Magnetization by Bulk Mirror Symmetry Broken Bi1- xSbx (012) with High Spin Hall Conductivity.

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 Bi1- xSbx (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 Bi1- xSbx (012), yielding an out-of-plane spin Hall conductivity of ∼ 1.12 × 10 5 ℏ 2 e Ω - 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.