Magnetization switching by asymmetric topological surfaces.

The development of spin-orbit-torque (SOT) devices has sparked considerable research interest, particularly in the quest for novel materials that exhibit high spin-to-charge conversion efficiencies for effective magnetic switching. However, optimizing structure and improving efficiency necessitate theoretical insights and material innovations. In this study, we employ first-principles calculations to investigate the persistent spin current in magnetic topological material MnSb2Te4. The weakly asymmetric topological surface states ensure that the spin currents in this system do not cancel out while facilitating high spin-to-charge conversion efficiency through spin-moment locking, thus unprecedentedly enabling SOT switching within a single layer. In experiments, we demonstrate a low critical current density of 7.3 × 105 A/cm2 for switching in epitaxial MnSb2Te4 thin films, alongside a substantial SOT efficiency of ∼41 at 6 K, consistent with micromagnetic simulations. Additionally, the development of in-situ epitaxial heterostructures of MnSb2Te4/FeTe0.9 allows for the extraction of an exchange-bias-induced effective field, thereby enabling field-free SOT switching within these heterostructures.