Anomalous Hall Effect of Pyrochlore Molybdate Nd_<b>2</b>Mo_<b>2</b>O_<b>7</b>

Abstract

Hall resistivity ρ H has been investigated for single crystals of pyrochlore molybdate Nd 2 Mo 2 O 7 . With decreasing temperature T , the anomalous Hall effect appears at around the Curie temperature T C (∼95 K). In the relatively high temperature region ( T > 60 K), ρ H can be described by the well-known equation ρ H = R 0 H +4 π R s M , where R 0 and R s are the ordinary and anomalous Hall coefficients, respectively, and M is the net magnetization predominantly contributed by the Mo spins. With further decreasing T , the ordering of the Nd moments, which is confirmed by neutron diffraction studies carried out by the present authors' group, induces marked change in the behavior of the anomalous part of ρ H . The behavior in the low temperature region has been found to be simply described by the equation ρ H = R 0 H +4 π R s M Mo +4π R s ' M Nd , where M Mo and M Nd are the net magnetizations of the Mo- and Nd-moments, respectively. This result and the T -dependence of R s and R s ' are quite different from those known for ordinary ferromagnets and might be related to the nonzero spin chirality observed in the present system.