Ferromagnetic resonance in ag coupled ni films

Abstract

We present an X-band ferromagnetic resonance (FMR) study of polycrystalline single Ni films and of two Ni layers separated by an Ag layer at room temperature. Films were deposited by sputtering on glass using Ag over- and underlays. The single Ni films have a FMR mode with a dependence of the resonance field on the angle α between the magnetic field and the plane in good agreement with theory. In samples with two Ni films coupled through an intervenient Ag layer, only one FMR mode is observed if the two Ni have identical thicknesses. When the films have different thicknesses a second weak resonance appears. The field difference between the two modes is a measure of the coupling between the Ni films. Results were obtained for a series of ssmplcs with the ,Ag thickness varying in the range 10 < t < 30 Å. Surprisingly, the two modes have opposite behavior with the variation of α, for all values of t. The results suggest that the coupling is antiferromagnetic when the field is parahel to the film plane and ferromagnetic when perpendicular, regardless of t.