PARAMETRIC AND MODULATION INSTABILITIES OF MAGNETOSTATIC SURFACE SPIN-WAVES IN FERROMAGNETIC-FILMS

First-order parametric instability, modulation instability and second- order instability processes for magnetostatic surface waves propagatin g in a pure yttrium iron garnet film are investigated in accordance wi th the relationship between the magnetostatic wave frequency and the i nternal magnetic field. The transitions from the second-order parametr ic instability, via the modulation instability, to the first-order par ametric instability (when the magnetic field is 720 Oe and the carrier frequency varies from 3.87 to 4.39 GHz), and the transitions from the first-order parametric instability to the second-order parametric ins tability via the modulation instability (when the carrier frequency is 3.5 GHz and the magnetic field varies from 427 to 647 Oe) are experim entally observed and explained. Dispersion characteristics of the magn etostatic surface waves are modified by introduction of a metallic gro und plane in order that the Lighthill criterion, as one of the prerequ isites for onset of the modulation instability, is fulfilled in a limi ted frequency range. Characteristics of magnetostatic surface wave mod ulation instability are studied by solving the nonlinear Schrodinger e quation. Dependencies of the modulation frequency induced by the modul ation instability on the carrier frequency and the magnetic field are found to be consistent with experimental data. (C) 1997 American Insti tute of Physics.