Analysis of optical magnetoelectric effect in GaFeO_3

TL;DR

This paper investigates the optical magnetoelectric effect in GaFeO_3, demonstrating how E1-M1 interference due to hybridization causes magnetoelectric spectra that depend on magnetization direction, aligning with experimental observations.

Contribution

It provides a microscopic calculation of the magnetoelectric optical spectra in GaFeO_3 considering E1, E2, and M1 processes, highlighting the role of hybridization in noncentrosymmetric environments.

Findings

Magnetoelectric spectra depend on magnetization direction.

Spectra calculated in the 1.0-2.5 eV range match experimental data.

E1-M1 interference from 4p-3d hybridization causes the effect.

Abstract

We study the optical absorption spectra in a polar ferrimagnet GaFeO_3. We consider the E1, E2 and M1 processes on Fe atoms. It is shown that the magnetoelectric effect on the absorption spectra arises from the E1-M1 interference process through the hybridization between the 4p and 3d states in the noncentrosymmetry environment of Fe atoms. We perform a microscopic calculation of the spectra on a cluster model of FeO_6 consisting of an octahedron of O atoms and an Fe atom displaced from the center with reasonable values for Coulomb interaction and hybridization. We obtain the magnetoelectric spectra, which depend on the direction of magnetization, as a function of photon energy in the optical region 1.0-2.5 eV, in agreement with the experiment.