Room temperature spin-orbit torque switching induced by a topological insulator

Abstract

Recent studies on the topological insulators have attracted great attention due to the rich spin-orbit physics and promising applications in spintronic devices. The strongly spin-moment coupled electronic states have been extensively pursued to realize efficient spin-orbit torque switching. However, so far current-induced magnetic switching with topological insulators has been observed only at cryogenic temperatures. Whether the topologically protected electronic states in topological insulators can benefit to spintronic applications at room temperature remains a controversial issue. In this thesis, spin-orbit-torque-induced magnetic switching is realized in topological insulator/ferrimagnet heterostructure at room temperature. Ferrimagnetic CoTb alloy with robust bulk perpendicular magnetic anisotropy is directly grown on a classical topological insulator Bi2 Se3. The low switching current density provides definitive proof of the high spin-orbit torque efficiency from topological insulators. The comparison between Bi2Se3 and (Bi,Sb)2Te3 with less bulk conductivity suggests the surface states plays a significant role in generated the efficient spin-orbit torques. Furthermore, the effective spin Hall angle of topological insulators is determined to be several times larger than commonly used heavy metals. These results demonstrate the robustness of topological insulators as a spin-orbit torque switching material and provide an avenue towards applicable topological insulator-based spintronic devices.