Spin wave spectrum of the quantum ferromagnet on the pyrochlore lattice Lu2V2O7

TL;DR

This study uses neutron scattering to analyze the spin wave spectrum of Lu2V2O7, revealing well-defined magnons and quantifying key Hamiltonian parameters, including exchange and Dzyaloshinskii-Moriya interactions.

Contribution

It provides the first detailed experimental determination of the spin wave spectrum and Hamiltonian parameters for the quantum ferromagnet Lu2V2O7 on the pyrochlore lattice.

Findings

Observed well-defined spin waves at all energies and wavevectors.

Quantified the nearest-neighbor Heisenberg exchange J and Dzyaloshinskii-Moriya interaction D.

Found D/J ratio consistent with magnon Hall effect models, but larger than ab initio predictions.

Abstract

Neutron inelastic scattering has been used to probe the spin dynamics of the quantum (S=1/2) ferromagnet on the pyrochlore lattice Lu2V2O7. Well-defined spin waves are observed at all energies and wavevectors, allowing us to determine the parameters of the Hamiltonian of the system. The data are found to be in excellent overall agreement with a minimal model that includes a nearest- neighbour Heisenberg exchange J = 8:22(2) meV and a Dzyaloshinskii-Moriya interaction (DMI) D =1:5(1) meV. The large DMI term revealed by our study is broadly consistent with the model developed by Onose et al. to explain the magnon Hall effect they observed in Lu2V2O7 [1], although our ratio of D=J = 0:18(1) is roughly half of their value and three times larger than calculated by ab initio methods [2].