Theory of microwave propagation in dielectric/magnetic film multilayer structures

We explore the theory of microwave propagation in dielectric films, on which thin metallic ferromagnetic films have been deposited. Our aim is to study coupling between the microwave electromagnetic fields, and spin excitations in the ferromagnetic films. We present quantitative studies of attenuation provided by coupling to spin excitations, for various model structures including superlattices. We find strong attenuation of the microwaves, for frequencies near the ferromagnetic resonance frequency of Fe. Modest magnetic fields place this resonance above 20 GHz, and allow its frequency to be tuned. We note a transmission minimum occurs near the frequency gamma(H-0 + 4 pi M-s), which is in the 70 GHz range for external magnetic fields H-0 of a few kilograms. We explore the dependence of these phenomena on film thicknesses, and argue that such structures will move suitably for high frequency microwave devices. (C) 1997 American Institute of Physics.