X-ray-absorption spectroscopy at the FeL2,3threshold in iron oxides

The influence of local order around the iron site on Fe 2p x-ray-absorption spectra is studied for α-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$, FeO, ${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$, and γ-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$. The experimental spectra are accounted for thanks to a configuration-interaction calculation of Fe ${\mathit{L}}_{2,3}$ x-ray-absorption edge shapes, explicitly taking into account the exact first-neighbor surrounding of the cation acting through crystal-field splitting and hopping terms. The peak’s splittings and intensities are well reproduced: the contributions of the various iron site symmetries and valencies are discriminated. The nature of insulating gap for each compound is deduced.