Spin wave measurements over the full Brillouin zone of multiferroic BiFeO3

TL;DR

This study comprehensively measures spin wave dispersion in multiferroic BiFeO3 using neutron scattering, revealing that a simple Heisenberg model with specific interactions accurately describes its magnetic excitations.

Contribution

First detailed spin wave dispersion measurement over the full Brillouin zone of BiFeO3 with a simple Heisenberg Hamiltonian model.

Findings

Spin waves extend up to 72.5 meV.

Heisenberg model with specific parameters explains the data.

Provides fundamental magnetic interaction parameters for BiFeO3.

Abstract

Using inelastic neutron scattering technique, we measured the spin wave dispersion over the entire Brillouin zone of room temperature multiferroic BiFeO3 single crystals with magnetic excitations extending to as high as 72.5 meV. The full spin waves can be explained by a simple Heisenberg Hamiltonian with a nearest neighbor exchange interaction (J=4.38 meV), a next nearest neighbor exchange interaction (J'=0.15 meV), and a Dzyaloshinskii-Moriya-like term (D=0.107 meV). This simple Hamiltonian determined, for the first time, for BiFeO3 provides a fundamental ingredient for understanding of the novel magnetic properties of BiFeO3.