Influence of domain wall pinning on the dynamic behavior of magnetic vortex structures: Time-resolved scanning x-ray transmission microscopy in NiFe thin film structures

Artificial domain wall pinning sites were created in micron-sized thin-film Ni80Fe20 structures, and their influence on the vortex dynamics was investigated by using time-resolved scanning transmission x-ray microscopy. The domain wall pinning sites were introduced by means of focused ion beam etching in the form of antidots. The vortex gyration frequency increased in square-shaped structures but not in similarly modified disk-shaped structures, where no domain walls are present. This demonstrates that the domain wall pinning is causing the increased frequency. The effect is explained by the confinement of the domain wall motion to the portion of the structure that is circumscribed by the antidots and is in agreement with micromagnetic simulations.