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

TL;DR

This study investigates the magnetic structure and anomalous Hall effect in Nd2Mo2O7 using neutron scattering, revealing that the chirality mechanism alone cannot explain the observed Hall resistivity behavior.

Contribution

The paper provides detailed neutron scattering analysis and material parameters for Nd2Mo2O7, and critically tests the chirality mechanism against experimental Hall effect data.

Findings

Neutron scattering data successfully reproduced by the proposed parameters.

Calculated spin chirality does not fully account for the Hall resistivity behavior.

Chirality mechanism alone is insufficient to explain the anomalous Hall effect in Nd2Mo2O7.

Abstract

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