Room-Temperature Spin-Orbit Torque Switching Induced by a Topological Insulator

Abstract

Recent studies on the magneto-transport properties of topological insulators (TI) 1-7 have attracted great attention due to the rich spin-orbit physics and promising applications in spintronic devices. Particularly the strongly spinmoment coupled electronic states have been extensively pursued to realize efficient spin-orbit torque (SOT) switching. However, so far current-induced magnetic switching with TI has only been observed at cryogenic temperatures. It remains a controversial issue whether the topologically protected electronic states in TI could benefit spintronic applications at room temperature. In this work, we report full SOT switching in a TI/ferromagnet bilayer heterostructure with perpendicular magnetic anisotropy at room temperature. The low switching current density provides a definitive proof on the high SOT efficiency from TI. The effective spin Hall angle of TI is determined to be several times larger than commonly used heavy metals. Our results demonstrate the robustness of TI as an SOT switching material and provide a direct avenue towards applicable TI-based spintronic devices.Spin-orbit coupling has been extensively studied for the conversion between charge current and spin current 8 . When neighbored with a ferromagnet (FM), non-equilibrium spins induced by the spin-orbit coupling can exert torques onto magnetic moments (Fig.

Manipulation of Magnetization by Spin–Orbit Torque

“…The effective field to current ratio and the spin Hall angle were detected by second‐harmonic methods and were found to be much larger than for HM/FM systems. Similar phenomena in topological insulator/ferromagnet systems were also observed by other groups . The ultralow‐power SOT switching by topological insulators has been shown by N. H. D. Khang et al .…”

The spin Hall effect of Bi-Sb alloys driven by thermally excited Dirac-like electrons

“…BiSb , we studied devices with three different t CoFeB (∼2, 3.4, and 4.3 nm). We find ξ DL of Bi 0.53 Sb 0.47 is of the same sign with that of Pt[45] and is consistent with previous reports on MBE-grown Bi 0.9 Sb 0.1[31] and stoichiometric Bi 2 Se 3[23,29] topological insulators. At t BiSb ∼8 nm, ξ DL reaches a maximum of ∼ 0.65.…”

Towards microscopic control of the magnetic exchange coupling at the surface of a topological insulator

“…The top axis in each panel shows the average distance between adatoms, corresponding to the measured coverage range within a statistical distribution [49] of 3d adatoms on the Bi 2 Te 3 (111) surface. In the case of Mn/Bi 2 M Te , 3 0 eff is already larger than the total magnetic moment at the lowest coverage, but it increases considerably in the range 0.01n0.03 ML, where it reaches values far beyond what can be expected for a single Mn atom, with a peak at n≈0.016 ML where M 0 eff reaches a value of 8.95 μ B . This is in stark contrast with the decrease of the magnitude of the XMCD and the consequent decrease of the total magnetic moment (see figure 5(a)) observed in the same coverage range.…”

“…Topological insulators (TIs) define a novel state of electronic matter, characterized by the coexistence of a bulk insulating gap and a non-degenerate metallic surface band. The interplay between TIs and magnetism is of great interest for future spintronics and low power devices [1][2][3][4]. In particular the discovery of the quantum anomalous Hall effect (QAHE) [5] led to intense research activities in magnetically doped TIs.…”