  We present a combined numerical, theoretical and experimental study on
stimulated three-magnon splitting in a magnetic disk in the vortex equilibrium
state. Our micromagnetic simulations and Brillouin-light-scattering results
confirm that three-magnon splitting can be triggered even below threshold by
exciting one of the secondary modes by magnons propagating in a waveguide next
to the disk. The experiments show that stimulation is possible over an extended
range of excitation powers and a wide range of frequencies around the
eigenfrequencies of the secondary modes. Rate-equation calculations predict an
instantaneous response to stimulation and the possibility to prematurely
trigger three-magnon splitting even above threshold in a sustainable manner.
These predictions are confirmed experimentally using time-resolved
Brillouin-light-scattering measurements and are in a good qualitative agreement
with the theoretical results. We believe that the controllable mechanism of
stimulated three-magnon splitting could provide a possibility to utilize
magnon-based nonlinear networks as hardware for reservoir or neuromorphic
computing.
