Temperature-Dependent Interplay of Dzyaloshinskii-Moriya Interaction and Single-Ion Anisotropy in Multiferroic BiFeO$_3$

TL;DR

This study investigates how temperature influences magnon excitations in multiferroic BiFeO$_3$, revealing the interplay of Dzyaloshinskii-Moriya interaction and single-ion anisotropy through neutron scattering and spin-wave analysis.

Contribution

It provides detailed temperature-dependent measurements of magnon spectra and elucidates the relationship between spin Hamiltonian parameters and structural changes in BiFeO$_3$.

Findings

Magnon spectra show features linked to Dzyaloshinskii-Moriya interaction and anisotropy.

Temperature affects exchange interactions and magnetic anisotropy.

Results connect spin Hamiltonian parameters with physical and structural properties.

Abstract

Low-energy magnon excitations in multiferroic BiFeO$_3$ were measured in detail as a function of temperature around several Brillouin zone centers by inelastic neutron scattering experiments on single crystals. Unique features around 1 meV are directly associated with the interplay of the Dzyaloshinskii-Moriya interaction and a small single-ion anisotropy. The temperature dependence of these and the exchange interactions were determined by fitting the measured magnon dispersion with spin-wave calculations. The spectra best fits an easy-axis type magnetic anisotropy and the deduced exchange and anisotropy parameters enable us to determine the anharmonicity of the magnetic cycloid. We then draw a direct connection between the changes in the parameters of spin Hamiltonian with temperature and the physical properties and structural deformations of BiFeO$_3$.