PARAMETRIC-EXCITATION OF MAGNETOSTATIC MODES IN THIN YTTRIUM-IRON-GARNET FILMS

Recently, equations of motion for the normal modes of normally magnetized thin films have been successful in predicting experimental auto-oscillation frequencies and onset pumping powers in circular yttrium iron garnet films under ferromagnetic resonance. These results have now been extended to include "hidden" modes, modes that do not couple directly to the pumping field. Using the equations of motion derived for this system, hidden modes are shown to be parametrically excited through processes analogous to the second-order Suhl instability. Through excellent agreement with experimental results, parametrically excited hidden modes are shown to be involved in features of the domain of auto-oscillation that were not previously understood. Numerical studies of the effects of degeneracy breaking in pairs of hidden modes show how small perturbations can fix the phases of parametrically excited modes. The random-phase approximation is shown to have a significant effect in simulations of the experiment.