One-magnon (electromagnon) light scattering in BiFeO3 single crystals

TL;DR

This study reports the observation of magnon and electromagnon Raman scattering in BiFeO3 single crystals at cryogenic temperatures, revealing temperature-dependent behavior and a magnon-reorientation transition linked to magnetoelectric coupling.

Contribution

First observation of magnon and electromagnon Raman scattering in BiFeO3 single crystals with detailed temperature dependence analysis.

Findings

Magnon frequency approximates a Brillouin function up to 280 K.

Diverging cross-section indicates a magnon-reorientation transition.

Magnons exhibit electric dipole moments due to magnetoelectric coupling.

Abstract

We observed Raman scattering from magnon in frequency range from 10 to 65 cm-1 in BiFeO3 single crystals at cryogenic temperatures; the temperature dependence of the magnon frequency at 18.2 cm-1 approximates an S=5/2 Brillouin function up to the temperature (280 K) at which the magnon becomes overdamped. The diverging cross-section and the frequency-shift at 140K and 200 K implies a magnon-reorientation transition as in orthoferrites. Magnons in polar materials such as BiFeO3 are often termed electromagnons meaning that they possess an electric dipole moment due to magnetoelectric coupling.