Real-space observation of standing spin-wave modes in a magnetic disk

In-plane standing spin-wave modes in a minute magnetic disk are directly observed by using time-resolved magneto-optical microscopy synchronized with microwaves. The time-resolved microscopy allowed us to obtain snapshots of standing spin-wave modes in a magnetic disk, which show a hourglass-like standing spin wave pattern. We found that the characteristic pattern is caused by spatially nonuniform magnetization and a strong microwave excitation in terms of finite element calculation and micromagnetic simulations. The technique we developed in this work allows us to access magnetization dynamics in microstructured magnets under strong microwave pumping.