Nonlinear Parallel-Pumped FMR: Three and Four Magnon Processes

The nonlinear response of a magnetic thin film subject to microwave radiation is quantitatively predicted in the steady state. Three- and four-magnon processes are shown to cause this nonlinearity with a strong dependence on magnetic bias field, microwave frequency, and applied power. Predictions are calculated using large-scale micromagnetic simulations executed on graphics processing units (GPUs) and include thermal fluctuations. A 2-D simulation paradigm is proposed for reducing the resource requirements while being able to capture the qualitative and quantitative behavior of the significant microwave-ferromagnet interactions in the parallel pumping configuration. A mathematical formalism specific to thin films is then developed to explain the aforementioned behavior of such magnetic materials based on their predicted magnon dispersion relation. The simulated predictions for high-power (nonlinear) performance are in close agreement with experiment even though the material parameters are only taken from low-power (linear) data.