FERRIMAGNETIC RESONANCE LINESHAPE ASYMMETRY DUE TO SUHL INSTABILITIES

We present calculations of the ferrimagnetic resonance lineshapes resu lting from second order Suhl instabilities for thin films and spheres. We find that whereas a spherical sample has a lineshape which is symm etrical around the resonant frequency, a thin film has an asymmetrical lineshape. The calculations are in agreement with measurements that w e have performed of the lineshape as a function of input power for thi n film samples of both barium ferrite and yttrium iron garnet. When th e magnetic field direction is changed from perpendicular to parallel t o the film plane, the asymmetry of the lineshape at magnetic resonance changes in opposite sense relative to the resonant field. Theoretical estimated of the critical microwave field necessary for second order Suhl instabilities to occur are in agreement with measured critical fi elds.