Magnetostatic coupling between ferromagnetic sandwich films with nonmagnetic intermediate layer

Uniaxial ferromagnetic double layered films with a nonferromagnetic intermediate layer (Au) were investigated with a quasi-statically increasing reverse dc field. The directions of the mean magnetizations in the magnetic films of the sandwich system and in simultaneously evaporated single layered films were measured. Torques, caused by the coupling between the two magnetic films of the system, were observed. From these torques a coupling field was determined. In addition the micromagnetic theory of a magnetostatic coupling field is given. In this theory coupling is assumed to be caused by the ripple stray fields, which penetrate the intermediate layer of the system. The coupling field given by this model depends on the applied field. Its calculated value agrees quantitatively with the experiment.