Directional Dichroism of X-Ray Absorption in a Polar Ferrimagnet GaFeO_3

TL;DR

This paper investigates the directional dichroism in x-ray absorption spectra of the polar ferrimagnet GaFeO_3, revealing the microscopic origin of the effect and comparing theoretical calculations with experimental data.

Contribution

The study provides a microscopic calculation of x-ray absorption dichroism in GaFeO_3, linking it to E1-E2 interference and hybridization effects, which is a novel insight.

Findings

Theoretical spectra match experimental shapes but have opposite signs.

Directional dichroism arises from E1-E2 interference in noncentrosymmetric environments.

The difference in absorption depends on magnetic field orientation.

Abstract

We study the directional dichroic absorption spectra in the x-ray region in a polar ferrimagnet GaFeO_3. The directional dichroism on the absorption spectra at the Fe pre-K-edge arises from the E1-E2 interference process through the hybridization between the 4p and 3d states in the noncentrosymmetric environment of Fe atoms. We perform a microscopic calculation of the spectra on a model of FeO_6 with reasonable parameter values for Coulomb interaction and hybridizations. We obtain the difference in the absorption coefficients when the magnetic field is applied parallel and antiparallel to the c axis. The spectra shus obtained have similar shapes to the experimental curves as a function of photon energy in the Fe pre-K-edge region, although they have opposite signs.