Room temperature magnetization switching in topological insulator-ferromagnet heterostructures by spin-orbit torques.

Abstract

Topological insulators with spin-momentum-locked topological surface states are expected to exhibit a giant spin-orbit torque in the topological insulator/ferromagnet systems. To date, the topological insulator spin-orbit torque-driven magnetization switching is solely reported in a Cr-doped topological insulator at 1.9 K. Here we directly show giant spin-orbit torque-driven magnetization switching in a Bi₂Se₃/NiFe heterostructure at room temperature captured using a magneto-optic Kerr effect microscope. We identify a large charge-to-spin conversion efficiency of ~1-1.75 in the thin Bi₂Se₃ films, where the topological surface states are dominant. In addition, we find the current density required for the magnetization switching is extremely low, ~6 × 10⁵ A cm^-2, which is one to two orders of magnitude smaller than that with heavy metals. Our demonstration of room temperature magnetization switching of a conventional 3d ferromagnet using Bi₂Se₃ may lead to potential innovations in topological insulator-based spintronic applications.