Mossbauer studies of ultrathin Fe/Pt multilayers

A series of ultrathin Fe/Pt multilayers, prepared by magnetron sputtering, were studied by GEMS and transmission MS. The Fe-layer thickness varied from 3 to 12.5 Angstrom and that of Pt from 5 Angstrom to 39 Angstrom. The 3 Angstrom/9 Angstrom Pt sample displays magnetic hyperfine structure at RT, while the 3 Fe/19 Pt sample is paramagnetic at RT, demonstrating the effect of interlayer interaction. Both samples display out-of-plane magnetic anisotropy with 39 degrees angle with respect to the vertical for the former and nearly 0 degrees angle for the latter. The analysis of the spectra of samples with thickness larger than one monolayer of Fe is done with components assigned to individual Fe monolayers. In all these cases a component appears with a hyperfine field larger by similar to 10% at RT and 17% at L.He than the corresponding values of alpha-Fe. This component is attributed to the first monolayer below the Fe/Pt interface in accordance with similar results in the Fe/Pd system and with theoretical predictions.