Observation of mixed-mode oscillations in spin-wave experiments

High-power ferromagnetic resonance experiments in a 1-mm-diam yttrium iron garnet sphere, driven at 8.9 GHz at room temperature, reveal evidence for a universal scenario not yet observed in this system, namely, the periodic-c haotic sequence. Well above the first-order Suhl instability threshold ( P/ P(C)similar to 6 dB), low-frequency (f similar to 200 kHz) auto-oscillation s consisting of large-amplitude peaks followed by n small undulations (mixe d-mode oscillations) have been observed. Both periodic and aperiodic trajec tories were detected with n=1, 2, 3, and 4, which are reminiscent of the so -called homoclinic chaos. A discussion is made on the basis of a standard t wo-mode model. (C) 1999 American Institute of Physics. [S0021-8979(99)75008 -5].