MOSSBAUER STUDY OF DIFFERENT MAGNETIC-PROPERTIES BETWEEN OPPOSITE INTERFACES OF FE(100)/AG(100) MULTILAYERS

A series of Fex(100)/Ag40(100) multilayers with x = 3, 6 and 9 monolayers (ML) were grown by MBE. Their crystallinity was verified by in situ RHEED. Their magnetic properties as well as their structural properties were analyzed by Fe-57 Mossbauer spectroscopy. The 3 ML film showed two Mossbauer components with parameters very different from those of bulk Fe. The 6 and 9 ML films exhibited 3 components, the additional one with very bulk-like parameters (and growing in intensity with Fe thickness). These results have led us to assign the two other components to the two interface regions, Fe/Ag and Ag/Fe. To confirm the assignment and distinguish the two interfaces, we grew three more 9 ML films, placing 2 ML Fe-57 in the bulk and at each interface, with the remaining 7 ML Fe-56. The Mossbauer hyperfine parameters of these sites were distinguished in a way consistent with the above assignment. In addition, we also investigated the temperature dependence of the magnetic hyperfine field for the three Fe sites. We conclude that the differing tetragonal distortions in the two interface regions are responsible for the appearance of the two interface sites.