Many-body effects in x-ray absorption and magnetic circular dichroism spectra within the LSDA+DMFT framework

The theoretical description of photoemission spectra of transition metals was greatly improved recently by accounting for the correlations between the d electrons within the local spin-density approximation (LSDA) plus dynamical mean-field theory (DMFT). We assess the improvement of the LSDA+DMFT over the plain LSDA in x-ray absorption spectroscopy, which---unlike the photoemission spectroscopy---is probing unocccupied electronic states. By investigating the L{}2,3$ edge x-ray absorption near-edge structure (XANES) and x-ray magnetic circular dichroism (XMCD) of Fe, Co, and Ni, we find that the LSDA+DMFT improves the LSDA results, in particular concerning the asymmetry of the L₃ white line. Differences with respect to the experiment, nevertheless, remain---particularly concerning the ratio of the intensities of the L₃ and L₂ peaks. The changes in the XMCD peak intensities invoked by the use of the LSDA+DMFT are a consequence of the improved description of the orbital polarization and are consistent with the XMCD sum rules. Accounting for the core hole within the final-state approximation does not generally improve the results. This indicates that to get more accurate L{}2,3$ edge XANES and XMCD spectra, one has to treat the core hole beyond the final-state approximation.