  We study the spin-wave dynamics in nanoscale antidot lattices based on Co/Pd
multilayers with perpendicular magnetic anisotropy. Using time-resolved
magneto-optical Kerr effect measurements we demonstrate that the variation of
the antidot shape introduces significant change in the spin-wave spectra,
especially in the lower frequency range. By employing micromagnetic simulations
we show that additional peaks observed in the measured spectra are related to
narrow shell regions around the antidots, where the magnetic anisotropy is
reduced due to the Ga+ ion irradiation during the focused ion beam milling
process of the antidot fabrication. The results point at new possibilities for
exploitation of localized spin waves in out-of-plane magnetized thin films,
which are easily tunable and suitable for magnonics applications.
