Depth-dependent magnetic characterization of Fe films on NiO(001)

We used nuclear hyperfine spectroscopies and a Fe-57 probe layer approach to Study the depth-dependent magnetic properties of ultrathin Fe films on NiO(0 0 1), a system exhibiting exchange bias. Conversion electron Mossbauer spectroscopy and nuclear resonance scattering of synchrotron radiation were employed. The samples were two Fe films with a thickness (8-10 ML) slightly above the critical thickness for the onset of ferromagnetism at room temperature, in which a 2 ML-thick probe layer, enriched in the,7 Fe Mossbauer isotope, was embedded at different depths from the Fe/NiO interface. Both techniques indicate that inside the film Fe has a metallic character, while at the interface with NiO different Fe phases are present. The main conclusion is that already a few monolayers from the interface with NiO the magnetic properties of Fe are bulk-like. (C) 2009 Elsevier B.V. All rights reserved.