In this work, the temporal aspects of two nonlinear spin wave processes, 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 into two magnons, each with a frequency near /2, while confluence refers to the subsequent combination of two of the split magnons into one with frequency. 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 shortwavelength spin waves for spintronic devices.

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Spin waves in micrometer-sized, patterned Y-shaped Permalloy structures were studied using micro-focus Brillouin light scattering (BLS) with a magnetic field applied in-plane. For in-plane magnetized thin films and microstrips, the dispersion relations depend on the angle of the magnetization with respect to the microstrip axis. BLS measurements show that spin waves generated in the two arms that form the top of the Y structure can be channeled into a longer magnetic microstrip that forms the base when the applied field is oriented perpendicular to the long axis of the base. In this configuration, the base supports surface spin waves. A comparison of the BLS data with micromagnetic simulations reveals that low-k spin waves generated by a microstrip antenna in the arms are converted to higher-k spin waves in the base, which may be useful for nanomagnonic applications.

The dynamic behavior of magnetic antivortices stabilized in patterned pound-key-like microstructures was studied using micro-focus Brillouin light scattering (micro-BLS) at frequencies above the gyrotropic mode (>1 GHz). Micro-BLS spectra obtained as a function of the frequency of a driving microwave field show an intricate spectrum for the antivortex state for an in-plane driving field. Spatial mode profiles for the strongest antivortex resonance frequencies, obtained for samples in the antivortex as well as the single domain states, show that while the symmetry of one of the observed resonances is relatively insensitive to the spin configuration, the antivortex exhibits a unique mode profile for the other. A comparison with micromagnetic simulations shows that the frequency and symmetry of the latter are consistent with one of the antivortex azimuthal modes. Furthermore, the simulations show that this mode involves coupling between the antivortex spin excitations and propagating spin waves in the structure legs, which may be useful for high-wavenumber spin wave generation.