Latent state in time-resolved nonlinear magnon scattering in thin films

The physics of nonlinear magnon scattering has been exploited in nonlinear microwave devices for wireless and satellite communication applications. The latent state, which is the time delay in the response to a microwave pulse, is required to be reduced for fast information communication. We have studied the latent state in time-resolved nonlinear magnon scattering in thin films, in both theory and experiment. The experiment is performed using phase-sensitive time-resolved heterodyne ferromagnetic resonance. The theory is a hybrid time-resolved model which uses an analytical equation of motion based on the Holstein-Primakoff transformation, and realistic micromagnetic simulation, in order to capture the magnon number change caused by the scattering. From the experiment, we find the latent state is a function of power, frequency, and material properties, which indicates the delay time scale is tunable by specific design. The origin of the latent state is the magnon redistribution, in that the uniform magnon mode (wavevector k=0) takes time to scatter into non-uniform magnon modes k≠0, which is reflected in the time-resolved magnon number of these modes.