Spin-orbit torques and magnetotransport properties of $α$-Sn and $β$-Sn heterostructures

Abstract

Topological insulators have emerged as an important material class for efficient spin-charge interconversion. Most topological insulators considered to date are binary or ternary compounds, with the exception of α-Sn. Here we report a comprehensive characterization of the growth, magnetotransport properties, and current-induced spin-orbit torques of α-Sn and β-Sn-based ferromagnetic heterostructures. We show that α-Sn grown with a Bi surfactant on CdTe(001) promotes large spin-orbit torques in a ferromagnetic FeCo layer at room temperature, comparable to Pt, whereas α-Sn grown without Bi surfactant and the non-topological phase, β-Sn, induce lower torques. The dampinglike and fieldlike spin-orbit torque efficiency in α-Sn with Bi are 0.12 and 0.18, respectively.Further, we show that α-Sn grown with and without Bi presents a spin Hall-like magnetoresistance comparable to that found in heavy metal/ferromagnet bilayers. Our work demonstrates direct and efficient charge-to-spin conversion in α-Sn ferromagnetic heterostructures, showing that α-Sn is a promising material for current-induced magnetization control in spintronic devices.