Progressive development of spin wave chaos in active-ring oscillators

This Letter reports the first experimental demonstration of progressive chaos development through four-wave mixing of spin wave amplified harmonics in magnonic active-ring oscillators. We find that the route to chaos represents a sequence of quasiperiodic regimes of oscillations and ultimately yields formation of a 3D torus in the phase space. The transition from the quasiperiodic oscillations to chaos proceeds through progressive spectrum stochastization during which the amplified harmonics gradually disappear.