Dzyaloshinskii-Moriya interaction in α−Fe2O3 measured by magnetic circular dichroism in resonant inelastic soft x-ray scattering

Abstract

Fe ${L}_{2,3}$-edge x-ray absorption spectra (XAS) and magnetic circular dichroism (MCD) in resonant inelastic x-ray scattering (RIXS) of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ were measured to identify the electronic structure responsible for its weak ferromagnetism caused by the Dzyaloshinskii-Moriya interaction (DMI) at room temperature. In contrast to negligible MCD in XAS, MCD in RIXS (RIXS-MCD) was clearly observed in the $dd$ excitation at 1.8 eV via excitation to charge-transfer states. Furthermore, RIXS-MCD showed a crystal orientation dependence, indicating that the observed RIXS-MCD originated from DMI. The observed RIXS-MCD is well described by ab initio charge-transfer multiplet calculations, revealing that the RIXS-MCD derives from spin flip excitations at delocalized ${e}_{\mathrm{g}}$ orbitals. By the combination of the experiments and calculations, RIXS-MCD has unraveled that the origin of DMI in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ is the ${e}_{\mathrm{g}}$ orbitals, which are strongly hybridized with the $2p$ orbitals of oxygen atoms. The results demonstrate the importance of RIXS-MCD for identifying the electronic structure related to DMI.