Studies of Anomalous Hall Effect and Magnetic Structure of Nd₂Mo₂O₇ –Test of Chirality Mechanism–

Abstract

Neutron scattering studies have been carried out under the magnetic fields\nH//[0_11] and H//[001] on a single crystal of Nd2Mo2O7, whose Hall\nresistivity(rhoH) exhibits quite unusual H- and temperature(T)-dependences.\nMaterial parameters such as the single ion anisotropies of the Mo- and Nd-\nmoments and exchange coupling constants among the Mo-Mo, Mo-Nd and Nd-Nd\nmoments, have been determined to reproduce various kinds of experimental data\ntaken as a function of H and T. For example, the neutron Bragg intensities,\nmagnetization curves and the magnetic specific heats have been reproduced by\nthe common parameters. By using the magnetic structure reproduced by these\nparameters, the spin chirality (chi) of Mo spins or the fictitious magnetic\nflux Phi proportional to chi has been calculated as a function of H and T by\nusing equation chi=<S1.S2x S3>, where the bracket means the statistical\naverage. (Note that we do not use the equation chi=<S1><S2>x<S3>, because the\nlocal nature of the chirality should be correctly considered.) Comparing the\ncalculated results with the observed rhoH, we can conclude that the unusual\nbehavior of rH cannot be understood consistently only by the chirality\nmechanism.\n