Control of magnon frequency combs in magnetic rings

Using Brillouin light scattering microscopy, we study the rich dynamics in magnetic disks and rings governed by nonlinear interactions, focusing on the role of vortex core dynamics on the spin-wave eigenmode spectrum. By strongly exciting quantized magnon modes in magnetic vortices, self-induced magnon Floquet states are populated by the intrinsic nonlinear coupling of magnon modes to the vortex core gyration. As a result, magnon frequency combs are formed. In magnetic rings, however, this generation is suppressed even when exciting the system over a large power range. To retrieve frequency combs by the rich nonlinear dynamics in rings, we apply external in-plane magnetic fields by which the vortex core is nucleated. Our findings demonstrate how to take active control of the nonlinear processes and, thereby, the generation of magnon frequency combs in magnetic structures of different topology.