Orgin of coupling in multilayered films

The existence of a coupling between the magnetizations of two ferromagnetic films, separated by a thin layer of Au or of Cr, has been demonstrated previously. We have studied the modification of this coupling by controlled oxidation, after evaporation of the intermediate layer. The interaction energy decreases in the same manner for both Cr and Au intermediate layers, independent of the evaporation temperature of these layers. The rate of decrease is a function of the temperature at which the first magnetic film is prepared. From these experiments we conclude that in both cases the coupling results from the existence of magnetic bridges between the magnetic layers, passing through gaps in the intermediate layer. A model for the behavior of the spins in such a bridge is presented and its consequences are compared with the experimental results.