MODULATIONAL INSTABILITY OF SURFACE MAGNETOSTATIC WAVES IN FERROMAGNETIC-FILMS

A modulational instability of the surface magnetostatic wave has been experimentally observed. It was found that, in the spectrum of an inte nse magnetostatic wave propagating in an in-plane magnetized yttrium-i ron-garnet film with a single metallic ground plane, symmetric satelli te frequencies appeared when the power of the initial wave was above a certain threshold value. Three-magnon decay processes having a low po wer threshold with respect to four-magnon self-action processes were f orbidden by the conservation laws for the momentum and energy. The cal culated modulation frequency and power threshold are in a good agreeme nt with measured values.