Electronic structures of α-${\mathrm{Fe}}_2$${\mathrm{O}}_3$ and ${\mathrm{Fe}}_3$${\mathrm{O}}_4$ from O K-edge absorption and emission spectroscopy

We present O K-edge absorption and emission spectra for α-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ and ${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$ obtained using a high-resolution-undulator soft-x-ray radiation source. The occupied and the unoccupied O p densities of states are obtained and compared with the valence-band photoemission results. While these results confirm that α-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ can be classified as a charge transfer or an intermediate-type insulator, they suggest that ${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$ is more likely of the Mott-Hubbard type. The excitation-energy dependence of the emission spectra is also discussed.