Ordered compounds and magnetic properties of metallic multilayers

In this paper we first give a brief review Of the different methods (first principles and semi-empirical) which can be used for theoretical studies of the magnetic properties of ultra thin sq systems from an electronic structure point of view and we discuss their application domains. Then, we give a few examples of recent works concerning ordered compounds and multilayers. First, we study the role of interfacial ordered compounds on the total magnetisation and the interlayer couplings for Fe/Pd, Ca/Ru and Co/Rh multilayers. We show that (i) the interlayer magnetic couplings in Fe/Pd superlattices are highly sensitive to interfacial mixing and (ii) the preserved magnetism at the Co/Rh interface can explain the strong interlayer couplings measured. Second, we study the magnetic orders in (FexCo1-x)/Mn-n superlattices for various Fe concentrations (x = 1, 3/4, 1/2, 1/4 and 0) of the ferromagnetic ordered compound with the ab initio augmented spherical wave method for collinear orders and with the tight binding real space recursion method for non-collinear orders. In perfect superlattices, we determine the angular dependence of the interlayer magnetic couplings when the magnetization of two successive ferromagnetic layers is rotated. We analyse these results as a function of the strength of the interfacial coupling and compare them to the dependencies given in the literature.