Time-resolved Study of Nonlinear Three-Magnon Processes in Yttrium Iron Garnet Films

In this work, the temporal aspects of two nonlinear spin-wave processes, i.e., three-magnon splitting and confluence, were investigated in a yttrium iron garnet film. Three-magnon splitting involves the conversion of a magnon at the microwave pumping frequency f(p) into two magnons, each with a frequency near f(p)/2, while confluence refers to the subsequent combination of two of the split magnons into one with frequency f(c) < f(p). Time-resolved Brillouin scattering measurements confirm that these processes occur close to the driving antenna (<1.7 mm away), which is expected. The data indicate, however, that magnons with larger group velocities are more likely to undergo confluence, which is not predicted by existing theory. Understanding the details of the splitting and confluence processes may have important implications for the use of short-wavelength spin waves for spintronic devices.