OSCILLATORY COUPLING BETWEEN INTERFACES IN METALLIC MULTILAYERS

We have developed a theory that views the total energy of an array of multilayers as a weighted average of bulk contributions corrected by a sum of single-interface and interface-interface interactions terms. We show that for metallic systems these interactions oscillate as functions of the appropriate interface-interface separations. Furthermore, we demonstrate that they are due to the same quantum-mechanical property of a degenerate Fermi liquid in a localized external potential as that which gives rise to the Friedel charge and magnetic oscillation around an impurity and the corresponding Ruderman-Kittel-Kasuya-Yoshida (RKKY) interactions. We argue that the recently discovered oscillatory magnetic coupling between magnetic layers separated by paramagnetic metallic layers should be accompanied by elastic interactions that give rise to periodic strain modulations, DELTAa/a, in the spacer layers. We illustrate the foregoing discussion by explicit calculation on an inhomogeneous jellium model.