Anomalous-Hall heat current and Nernst effect in the ferromagnet CuCr_2Se_{4-x}Br_x

TL;DR

This paper investigates the anomalous-Hall heat current and Nernst effect in the ferromagnet CuCr2Se4-xBrx, revealing how the off-diagonal Peltier term varies with hole density and lifetime, and challenging existing models.

Contribution

It provides experimental measurements of the anomalous-Hall heat current's dependence on hole density and lifetime, and identifies a fixed microscopic geometric area influencing its magnitude.

Findings

α_xy is independent of τ at low temperatures

The magnitude of α_xy is determined by a geometric area ~34 Ų

Results challenge some existing models of the Nernst effect in ferromagnets

Abstract

In a ferromagnet, an anomalous-Hall heat current, given by the off-diagonal Peltier term $\alpha_{xy}$, accompanies the anomalous Hall current. By combining Nernst, thermopower and Hall experiments, we have measured how $\alpha_{xy}$ varies with hole density and lifetime $\tau$ in $\rm CuCr_2Se_{4-x}Br_x$. At low temperatures $T$, we find that $\alpha_{xy}$ is independent of $\tau$, consistent with anomalous-velocity theories. Its magnitude is fixed by a microscopic geometric area ${\cal A}\sim 34 \mathrm{\AA}^2$. Our results are incompatible with some models of the Nernst effect in ferromagnets.