THEORIES OF LONG-RANGE OSCILLATORY EXCHANGE COUPLING IN MAGNETIC MULTILAYERS

In the first part of this paper we present a critical review of recent theoretical studies of long range oscillatory coupling in magnetic multilayers. In the second part we discuss our recent first-principles self-consistent spin-polarized total energy calculations for fcc Co/Cu multilayers. In contrast to simplified theories, our studies take proper account of structural and chemical effects arising from the presence of the Co slabs, as well as their magnetic effects. Using local spin density functional theory and collinear spin arrangements, we obtain long- as well as short-period oscillatory behavior. We also demonstrate that the oscillatory components are strongly dependent on interfacial orientation. The multiperiodicity and orientation dependence can be interpreted in terms of the topology of the bulk Cu Fermi surface. In spite of the limited range of Cu spacer thicknesses examined, we are able to make rough estimates of oscillatory periods; these are in reasonable agreement with experiment.