Apparent sixfold configurational anisotropy and spatial confinement of ferromagnetic resonances in hexagonal magnetic antidot lattices

Abstract

The static and dynamic properties of hexagonal lattices of magnetic antidots have been studied using micromagnetic simulations and semianalytical modeling. The theoretical model is based on the Landau–Lifshitz equation and is developed for the case of comparable magnitudes of the field and linewidth of the ferromagnetic resonance (FMR). It is found that the antidot pattern induces an apparent sixfold configurational anisotropy manifesting itself via an anisotropic resonant response of the patterned film. However, calculations performed with a reduced damping reveal that the resonance peak consists of three different quasiuniform modes of the magnetization dynamics, with the resonant field of each of them showing a twofold variation with respect to the in-plane orientation of the applied magnetic field. The easy axes of the resonant modes are mutually rotated by 60° and combine to yield the observed sixfold configurational anisotropy. Micromagnetic calculations of the local dynamic susceptibility allow us to attribute each absorption line to a different area of the sample. Finally, we analyze the effect of the antidot radius and the lattice period on the broadening of the uniform FMR line in comparison with the uniform FMR mode of the corresponding continuous film.