Large anomalous Nernst effect in thin films of the Weyl semimetal Co2MnGa

TL;DR

This study reveals that Co2MnGa thin films exhibit a large anomalous Nernst effect at room temperature, with its magnitude strongly dependent on film thickness and temperature, highlighting potential for spin-caloritronic applications.

Contribution

It provides the first systematic analysis of the temperature-dependent anomalous Nernst effect in Co2MnGa thin films, comparing different thicknesses and elucidating possible microscopic mechanisms.

Findings

Co2MnGa thin films show a large anomalous Nernst effect of -2μV/K at 300K.

The Nernst effect varies significantly with temperature and film thickness.

The microscopic origin involves complex contributions from skew-scattering, side-jump, or Berry phase.

Abstract

The magneto-thermoelectric properties of Heusler compound thin films are very diverse. Here, we discuss the anomalous Nernst response of Co$_2$MnGa thin films. We systematically study the anomalous Nernst coefficient as a function of temperature, and we show that unlike the anomalous Hall effect, the anomalous Nernst effect in Co$_2$MnGa strongly varies with temperature. We exploit the on-chip thermometry technique to quantify the thermal gradient, which enables us to directly evaluate the anomalous Nernst coefficient. We compare these results to a reference CoFeB thin film. We show that the 50-nm-thick Co$_2$MnGa films exhibit a large anomalous Nernst effect of -2$\mu$V/K at 300 K, whereas the 10-nm-thick Co$_2$MnGa film exhibits a significantly smaller anomalous Nernst coefficient despite having similar volume magnetizations. These findings suggest that the microscopic origin of the anomalous Nernst effect in Co$_2$MnGa is complex and may contain contributions from skew-scattering, side-jump or intrinsic Berry phase. In any case, the large anomalous Nernst coefficent of Co$_2$MnGa thin films at room temperature makes this material system a very promising candidate for efficient spin-caloritronic devices.