The role of dipole coupling in multilayers

Abstract

This work considers the role of magnetic dipole coupling in multilayers typically comprising a ferromagnetic material separated by a nonmagnetic metal spacer, e.g., NiFe/Ta. It has been suggested previously that dipolar fields may play an important role in the coupling of magnetic layers through a nonmagnetic spacer, in particular where surface roughness at the interface is significant. This work considers a first-order calculation of the dipole coupling energy and magnetic field between two adjacent layers. It is shown that dipole coupling energies originating from surface corrugations can behave in the same manner as a coercive field in terms of dependence on nonmagnetic spacer thickness and the degree of roughness. Interestingly, calculations also show that both ferromagnetic- and antiferromagnetic-like coupling can be explained in terms of this model. The role of the spacer thickness, magnetic layer thickness, and the form of the roughness is discussed.