MÖssbauer Measurements of Interfacial Magnetism of MBE Grown FE(100)/AG(100) Multilayers

Multilayers of Fe(100)/Ag(100) were grown by MBE and analyzed with in situ RHEED and MÖssbauer spectroscopy. These films had a constant Ag layer thickness of 40 monolayers (ML) and varying Fe layer thicknesses of 3, 6, and 9 ML. Using MÖssbauer spectroscopy the presence of three Fe sites was inferred. From considerations of the hyperflne parameters and the relative intensities of the sextets, we assign one site to the bulk, and one to each interface: Fe on Ag and Ag on Fe. We believe that one explanation of this is differing tetragonal distortions at the two interfaces. Consequently, another series of films was grown in an attempt to distinguish these sites. These films were essentially identical to the 9 ML film above, but the Fe layers were composed of 56Fe, with a 2 ML 57Fe probe layer effused at the bulk and at each interface in turn. At this point 57Fe MÖssbauer spectroscopy was used to determine the hyperfine field and its temperature dependence for each of the three sites.