Effects of impurities on the exchange coupling in magnetic metallic multilayers

In this work the variation of the exchange coupling between magnetic layers across a non-magnetic spacer layer, due to impurities of the magnetic material in the spacer, is calculated. The impurities are treated in the dilute limit and beyond it. It is shown that the change per impurity is comparable to the unperturbed coupling per atom, and that it oscillates as a function of spacer layer thickness with the same period as that coupling, though with a different phase. The most favourable magnetic moment orientation of the impurity is found for some spacer layer thicknesses and impurity positions. It is also shown that the short-period oscillations of the coupling may be much more affected by the presence of impurities than the long-period ones.