The chemical structure of (Fe,Co)/Pt superlattices, which had recently shown high uniaxial magnetocrystalline anisotropy combined with high saturation magnetic moments, was investigated. In particular, the homogeneity of the (Fe,Co) alloy was studied with a combination of X-ray and neutron reflectometry; the latter in a configuration where magnetic scattering was negligible. It was deduced, with support from off-specular X-ray reflectivity patterns and corresponding simulations, that the lower (Fe,Co)-on-Pt interface contains more Co than the upper Pt-on-(Fe,Co) interface. This could occur as Co interdiffuses into Pt more easily than Fe, as shown by density-functional calculations. The effect of this interdiffusion and segregation on the uniaxial anisotropy was discussed, and it was found that the previously observed discrepancy between experimental and theoretical anisotropy values could be quantitatively accounted for

Segregation and Interdiffusion in (Fe,Co)/Pt Superlattices. M.Björck, G.Andersson, B.Sanyal, M.Hedlund, A.Wildes: Physical Review B, 2009, 79[8], 085428