Theoretical prediction and experimental evidence of a novel oscillatory behaviour of interlayer magnetic coupling

The interlayer magnetic coupling between ferromagnetic layers separated by a non-magnetic spacer layer is investigated with emphasis on the role of the non-magnetic overlayer. By using a recently proposed theory of interlayer coupling, which expresses the coupling in terms of quantum interferences due to electron confinement, it is predicted that the coupling oscillates vs. overlayer thickness, with a period related to the Fermi surface of the latter. This prediction has been confirmed experimentally on Au/Co/Au/Co/Au(111) films, with an oscillation period vs. Au overlayer thickness of 5 atomic layers, in good agreement with the predicted value (4.8 atomic layers).