Neutron scattering studies of pyrochlore compound Nd₂Mo ₂O₇ in magnetic field

Neutron diffraction studies have been carried out in the applied magnetic field H(|| [011]) on a single crystal of pyrochlore ferromagnet Nd ₂Mo₂O₇, whose Hall resistivity (PH) has been reported to have quite unusual magnetic field (H)- and temperature (T)-dependences. The intensities of the observed magnetic reflections have been reproduced at 1.6 K as a function of H, by considering the change of the magnetic structure with H, where effects of the exchange fields at the Mo and Nd sites induced by the Mo-Mo and Mo-Nd exchange interactions and the single ion anisotropies of Mo- and Nd-moments are considered. From the H-dependent magnetic structure, the H-dependence of PH has been calculated by using the chiral order mechanism. By comparing the result with the H-dependence of the observed PH, it is found that the chiral order mechanism does not work well in the present system.