Many-body Approach for XAS and XMCD Applied to Ferrites

X-ray absorption spectroscopy is an important tool to extract element-specific information about the electronic structure, magnetism and in particular electronic correlation effects.

Ab initio calculations have a hard time reproducing the 2p to 3d excitation, in particular for strongly correlated materials and significant influences due to the core-hole. In this work, a combination of density functional theory and multiplet ligand field theory is used to bridge this gap. For this, we calculate parameters from first principles and use them to construct a single-impurity Anderson model by projecting the local Hamiltonian and the hybridization function onto the 3d states. We apply this method among other things NiFe₂O₄, CoFe₂O₄ and Fe₃O₄ and find systematically good agreement with the experiment for both XAS and XMCD spectra.