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

Abstract

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