Interplay between magnetic and lattice excitations in BiFeO$_3$

TL;DR

This study uses Raman scattering to explore the interaction between magnetic and lattice excitations in BiFeO$_3$, revealing strong coupling effects and identifying two-magnon excitations with temperature-dependent behavior.

Contribution

It demonstrates the coupling between magnetic and lattice excitations in BiFeO$_3$ through Raman spectroscopy, highlighting the energy shift and Fano lineshape of a phonon overtone.

Findings

Strong coupling between magnetic and lattice excitations in BiFeO$_3$

Identification of two-magnon excitation with temperature dependence

Observation of Fano lineshape indicating interaction effects

Abstract

We have performed Raman scattering investigations on the high energy magnetic excitations in a BiFeO$_3$ single crystal as a function of both temperature and laser excitation energy. A strong feature observed at 1250 cm$^{-1}$ in the Raman spectra has been previously assigned to two phonon overtone. We show here that its unusual frequency shift with the excitation energy and its asymmetric temperature dependent Fano lineshape reveal a strong coupling to magnetic excitations. In the same energy range, we have also identified the two-magnon excitation with a temperature dependence very similar to $\alpha$-Fe$_2$O$_3$ hematite.