  Neutron diffraction studies have been carried out in the applied magnetic
field H(//[011]) on a single crystal of pyrochlore ferromagnet Nd2Mo2O7, whose
Hall resistivity(r_H) 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 r_H
has been calculated by using the chiral order mechanism. By comparing the
result with the H-dependence of the observed r_H, it is found that the chiral
order mechanism does not work well in the present system.
