Fine structure and auto-oscillations of subsidiary absorption in tangentially magnetized yig films

Nonlinear ferromagnetic-resonance phenomena in tangentially magnetized yttrium-iron-garnet films are studied. The auto-oscillation and the fine-structure phenomena are found to appear and disappear simultaneously. The auto-oscillation frequency changes with the d.c. field within the range of a single fine-structure peak. Data analysis implies that this peak does not represent a single spin-wave mode but many groups of spin waves. This innomogeneous broadening and the inter peak spacing are analyzed and explained in terms of conventional dispersion relations. A careful recording of the lineshape shows that it is essentially a rectangle. An attempt to explain this shape in terms of Suhl's theory is made. These findings support the assertion that a fine-structure peak is due to a fine dip in the butterfly curve and usually represents many groups of parametrically excited spin waves.