Spin-orbit torques and magnetotransport properties of $\alpha$-Sn and $\beta$-Sn heterostructures

TL;DR

This study demonstrates that $ ext{α}$-Sn, especially when grown with Bi surfactant, exhibits large spin-orbit torques and efficient charge-to-spin conversion, making it a promising material for spintronic applications.

Contribution

It provides a comprehensive characterization of $ ext{α}$-Sn and $eta$-Sn heterostructures, highlighting $ ext{α}$-Sn's potential for efficient spin-charge interconversion in spintronics.

Findings

$ ext{α}$-Sn with Bi induces large spin-orbit torques comparable to Pt.

$ ext{α}$-Sn exhibits spin Hall-like magnetoresistance similar to heavy metal/ferromagnet bilayers.

$ ext{β}$-Sn induces lower torques than $ ext{α}$-Sn with Bi.

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 $\alpha$-Sn. Here we report a comprehensive characterization of the growth, magnetotransport properties, and current-induced spin-orbit torques of $\alpha$-Sn and $\beta$-Sn-based ferromagnetic heterostructures. We show that $\alpha$-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 $\alpha$-Sn grown without Bi surfactant and the non-topological phase, $\beta$-Sn, induce lower torques. The dampinglike and fieldlike spin-orbit torque efficiency in $\alpha$-Sn with Bi are 0.12 and 0.18, respectively. Further, we show that $\alpha$-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 $\alpha$-Sn ferromagnetic heterostructures, showing that $\alpha$-Sn is a promising material for current-induced magnetization control in spintronic devices.