OBSERVATION OF NONLINEAR COUPLED PHOTON-MAGNON OSCILLATIONS IN YIG

Nonequilibrium spin waves excited by the parallel pumping in an yttriu m iron garnet placed in a microwave cavity was studied by means of add itional weak microwave signal. The response of the probe signal repres ented a two-hump spectrum just above the threshold of parametric insta bility. It corresponds to mixed oscillations of photons and magnons an d demonstrates that the parametric spin-wave pair behaves as a single- mode oscillator nonlinearly coupled with the electromagnetic mode of m icrowave cavity. We observed another splitting in the spectrum before the onset of auto-oscillations. It is assumed to indicate that this st eady state of parametric system consists of two different parametric s pin-wave pairs. Theoretical calculations which consider coupled system s of resonator mode and magnetic sample are found to be in good agreem ent with the experimental data.