Local magnetic effects of interface alloying in Fe/Co superlattices

Effects of interface alloying and the thickness dependence of magnetic properties of Fe/Co(001) multilayers have been investigated. The thicknesses of the Fe layers have been varied between two and 14 monolayers while the Co layers have been held constant at 7 ML. From conversion electron Mossbauer spectroscopy (CEMS) measurements and electronic structure calculations it is found that the magnitude of the Fe magnetic hyperfine field is larger close to the interface and smaller in the middle of thick (<= 9 ML) Fe layers. For a thinner Fe layer (<= 5 ML) the largest field is found in the centre of the Fe layer. By modelling the effects of interface alloying from earlier data for bulk Fe-Co alloys, and comparing with the experimental results, the degree of interface alloying is estimated to be 2-3 ML at each interface.