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

We propose and demonstrate a quantitative noncontact measurement method for the thermal Hall effect (THE) based on magnetic-field-modulated lock-in thermography (LIT). This method enables visualization of THE-induced temperature change and quantitative estimation of the thermal Hall angle \ensuremath{\theta}${}_{\mathrm{THE}}$ 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 \ensuremath{\kappa}${}_{xx}$, we also quantify the transverse thermal conductivity \ensuremath{\kappa}${}_{xy}$. We validate our measurement methods by estimating \ensuremath{\theta}${}_{\mathrm{THE}}$, \ensuremath{\kappa}${}_{xx}$, and \ensuremath{\kappa}${}_{xy}$ in a ferromagnetic Heusler alloy ${\mathrm{Co}}_{2}\mathrm{Mn}\mathrm{Ga}$ slab showing large THE.