Spin-Orbit Torque and Nernst Effect in Bi-Sb/Co Heterostructures

TL;DR

This study investigates the Nernst effect in Bi-Sb/Co heterostructures, revealing its potential to mimic spin-orbit torque signals and thus affect the accuracy of spin-Hall angle measurements.

Contribution

It demonstrates that the ordinary Nernst effect can produce signals similar to spin-orbit torque, highlighting the need for careful interpretation in spintronic experiments.

Findings

Large second harmonic voltage due to Nernst effect observed

Nernst effect mimics spin-orbit torque angular dependence

Potential overestimation of spin-Hall angle in measurements

Abstract

Harmonic measurements of the longitudinal and transverse voltages in Bi-Sb/Co bilayers are presented. A large second harmonic voltage signal due to the ordinary Nernst effect is observed. In experiments where a magnetic field is rotated in the film plane, the ordinary Nernst effect shows the same angular dependence in the transverse voltage as the damping-like spin-orbit torque and in the longitudinal voltage as the unidirectional spin-Hall magneto-resistance respectively. Therefore, the ordinary Nernst effect can be a spurious signal in spin-orbit torque measurements, leading to an overestimation of the spin-Hall angle in topological insulators or semimetals.