Giant Hall Switching by Surface-State-Mediated Spin-Orbit Torque in a Hard Ferromagnetic Topological Insulator

Topological insulators (TI) and magnetic topological insulators (MTI) can apply highly efficient spin-orbit torque (SOT) and manipulate the magnetization with their unique topological surface states (TSS) with ultrahigh efficiency. Here, efficient SOT switching of a hard MTI, V-doped (Bi,Sb)2Te3 (VBST), with a large coercive field that can prevent the influence of an external magnetic field, is demonstrated. A giant switched anomalous Hall resistance of 9.2 k Omega is realized, among the largest of all SOT systems, which makes the Hall channel a good readout and eliminates the need to fabricate complicated magnetic tunnel junction (MTJ) structures. The SOT switching current density can be reduced to 2.8 x 105 A cm-2, indicating its high efficiency. Moreover, as the Fermi level is moved away from the Dirac point by both gate and composition tuning, VBST exhibits a transition from edge-state-mediated to surface-state-mediated transport, thus enhancing the SOT effective field to (1.56 +/- 0.12) x 10-6 T A-1 cm2 and the interfacial charge-to-spin conversion efficiency to 3.9 +/- 0.3 nm-1. The findings establish VBST as an extraordinary candidate for energy-efficient magnetic memory devices. Highly efficient current-driven spin-orbit torque (SOT) switching is observed in a hard ferromagnetic topological insulator (TI), V-doped (Bi,Sb)2Te3 (VBST), with a record large switched anomalous Hall resistance of 9.2 k Omega by current. The SOT efficiency is significantly enhanced by Fermi level tuning, as VBST exhibits a transition from edge-state-mediated to surface-state-mediated transport. image