Magnetotransport phenomena in a metallic ferromagnet on the verge of Mott transition: Sm2Mo2O7

Abstract

Magnetotransport phenomena have been investigated for a metallic ferromagnet, ${\mathrm{Sm}}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{7},$ locating on the verge of Mott transition. Large negative magnetoresistance (MR) is observed around the Curie temperature ${(T}_{C})$ for a single crystal, and well below ${T}_{C}$ as well for a polycrystalline sample. The low-temperature MR observed in the polycrystalline sample is ascribed to the tunneling MR across grain boundaries. The MR in the single crystal above ${T}_{C}$ is proportional to the square of the field-induced magnetization. The MR magnitude correlated with the carrier density roughly obeys the general tendency among ferromagnetic metals, recently derived by Majumdar et al. Both ordinary and anomalous Hall coefficients show sign reversal just below ${T}_{C},$ perhaps due to the change of Fermi-surface topology with increasing spin polarization.