Observation of Robust FMR in Permalloy Quasiperiodic Arrays

We have used ferromagnetic resonance (FMR) at fixed frequency 9.7 GHz to investigate permalloy thin films patterned with antidots to form a five-fold quasicrystal pattern. For DC applied fields H below 3.5 kOe, we observed robust FMR spectra exhibiting two-fold rotational symmetry instead of the five-fold symmetry expected for quasicrystals. Dynamic micromagnetic simulations of the FMR spectra performed at H = 1 kOe and 12 kOe exhibit two-fold and ten-fold rotational symmetry, respectively. The ten-fold symmetry observed in simulations is consistent with a saturated state of isolated write fields. We infer the two-fold rotational symmetry observed for H = 1 kOe is due to an unsaturated state of five-fold write fields closely spaced on a square lattice.