Dispersion characteristics of magnetostatic surface waves in a two-layer ferromagnetic film

The dispersion characteristics (dispersion and isofrequency curves and dispersion surfaces) of magnetostatic surface waves propagating in an arbitrary direction in a two-layer ferromagnetic film are investigated. The shapes of these curves and surfaces are studied at different ratios between the saturation magnetizations of the ferromagnetic layers, and the conditions for existence of external waves (always forward) and internal waves (forward and backward or only forward) are determined.