Anomalous Nernst Effects in Pyrochlore Molybdates with Spin Chirality

Abstract

The transverse thermoelectric (Nernst) effect on pyrochlore molybdates is investigated experimentally. In ${\mathrm{Nd}}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Sm}}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{7}$ with the spin chirality, the Nernst signal, which mostly arises from the transverse heat current (or equivalently the transverse Peltier coefficient ${\ensuremath{\alpha}}_{xy}$), shows a low-temperature (20--30 K) positive extremum, whereas it is absent in $({\mathrm{Gd}}_{0.95}{\mathrm{Ca}}_{0.05}{)}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{7}$ with no single-spin anisotropy of the rare-earth ion and hence with no spin chirality. The correlation between the Hall conductivity ${\ensuremath{\sigma}}_{xy}$ and ${\ensuremath{\alpha}}_{xy}$ in ${\mathrm{Nd}}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{7}$ also indicates the spin chirality plays a significant role in the spontaneous (anomalous) Nernst effect.