CONTRIBUTION OF QUANTUM-WELL STATES TO THE RKKY COUPLING IN MAGNETIC MULTILAYERS

We calculate the RKKY coupling between two magnetic layers separated by a nonmagnetic spacer, with scattering potentials added to represent changes in environment between the layers. For the case of a spacer potential well of depth V, the usual pi/k(F) oscillation period is superseded by one much longer, piHBAR/square-root 2mV. For a deep potential well (V is similar to epsilon(F)), the RKKY interaction becomes purely ferromagnetic for spacings greater than a few angstroms. Scattering potentials localized at the interfaces produce a phase shift in the RKKY oscillations. We discuss evidence for these effects in experimental systems.