Oxidation effects in epitaxial Fe3O4 layers on MgO and MgAl2O4 substrates studied by X-ray absorption, fluorescence and photoemission

Fe3O4 films of different thickness were epitaxially grown on single crystal MgO and MgAl2O4 substrates and studied by X-ray absorption, X-ray photoemission spectroscopy and X-ray fluorescence (XF). All samples were prepared by pulsed laser deposition (PLD) and some of them were covered by in situ prepared thin BaTiO3 protecting layer. The photoemission (VG ESCALAB 220i-XL) and absorption (total electron yield mode) measurements on epitaxial Fe3O4 films demonstrate the important role of the protecting layer to prevent the further oxidation of Fe3O4 to Fe2O3 in the case of thin films (2.5 nm range). The resonant XF (X-ray monochromator XES 300 using synchrotron radiation at the U41-PGM beam-line at BESSY II) measurements at excitation energy 710 eV (Fe L3 absorption edge) demonstrate the effect of the Fe 3d–O 2p hybridization in the iron oxide layers. Information about local partial densities of states was obtained for the oxidized Fe3O4 film from a comparative analysis of the Fe L and O K XF and the valence-band photoelectron spectra.