Stoichiometry of Fe3-δO4(111) ultrathin films on Pt(111) -: art. no. 214408

The composition and magnetic properties of two types of ultrathin Fe3-deltaO4(111) films grown epitaxially on Pt(111) have been characterized using conversion electron Mossbauer spectroscopy (CEMS) and x-ray magnetic circular dichroism (XMCD). CEMS data from both films indicate that the magnetic moments lie in-plane and that a paramagnetic contribution is present that is not seen in spectra of bulk magnetite samples. The XMCD results are in good agreement with theoretical calculations, enabling the stoichiometry of the films to be determined as Fe3O4 and Fe2.91O4. The concentrations of both the tetrahedral Fe3+ and octahedral Fe2+ ions are reduced in the nonstoichiometric film, the decrease in the tetrahedral site probably being due to disorder. CEMS consistently yields a high tetrahedral:octahedral ratio of about 0.7:1, probably because of a contribution from a nonstoichiometric FeO interface layer.