Synchronization among spin-wave amplitudes in chaotic nonlinear ferromagnetic resonance

A model of chaos in high-power ferromagnetic resonance in coincidence regim e, based on three-magnon interactions of the uniform mode with a group of p airs of parametric spin waves, is investigated numerically. The results are interpreted from the point of view of chaotic synchronization theory. If a ll spin waves are identical, all of them are excited above the first-order Suhl instability threshold and in the chaotic regime their amplitudes show marginal synchronization, i.e. they differ only by a multiplicative factor, constant in time. If spin waves have slightly different instability thresh olds, only one or few of them are excited. In the latter case, addition of weak thermal noise changes the results qualitatively. For low rf field ampl itude, but above the threshold for chaos, still only few spin-wave pairs ar e excited above the thermal level. For higher rf field amplitude all spin w aves in the group are excited, and their amplitudes are not synchronized. T hese results suggest that low correlation dimension of chaotic attractors, observed often in nonlinear ferromagnetic resonance, can be connected with chaotic synchronization among spin-wave amplitudes, in particular just abov e the threshold for chaos.