Quantitative noncontact measurement of thermal Hall angle and transverse thermal conductivity by lock-in thermography

TL;DR

This paper introduces a noncontact, lock-in thermography-based method to quantitatively measure the thermal Hall effect, including the thermal Hall angle and transverse thermal conductivity, in magnetic materials.

Contribution

The authors develop and validate a novel noncontact measurement technique combining lock-in thermography with magnetic field modulation to quantify thermal Hall parameters.

Findings

Successfully measured thermal Hall angle in Co₂MnGa alloy.

Quantified transverse thermal conductivity using the proposed method.

Demonstrated visualization of THE-induced temperature changes.

Abstract

We propose and demonstrate a quantitative noncontact measurement method for the thermal Hall effect (THE) based on magnetic-field-modulated lock-in thermography. This method enables visualization of THE-induced temperature change and quantitative estimation of the thermal Hall angle $\theta_{\rm THE}$ by applying periodic magnetic fields to a sample and obtaining the first harmonic response of thermal images. By combining this method with LIT-based measurement techniques for the longitudinal thermal conductivity $\kappa_{xx}$, we also quantify the transverse thermal conductivity $\kappa_{xy}$. We validate our measurement methods by estimating $\theta_{\rm THE}$, $\kappa_{xx}$, and $\kappa_{xy}$ in a ferromagnetic Heusler alloy Co$_2$MnGa slab showing large THE.