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.