Excitation of chaotic spin waves through modulational instability.

This Letter reports the first experimental demonstration of chaotic excitations through modulational instability for waves with a repulsive nonlinearity. The experiments were carried out for surface spin waves in a magnetic thin film strip in an active feedback ring configuration. At a low ring gain level, one observes the self-generation of one eigenmode. With an increase in the ring gain, one observes the production of additional modes and the onset and enrichment of chaotic behaviors.