Evolution of Spin Wave Modes in Periodically Perturbed Thin Films

The transition from a continuous thin film to a magnonic crystal is studied by ferromagnetic resonance (FMR).
Ion irradiation as well as reactive ion beam etching were used to realize a periodic modulation of the sample surface after patterning by electron beam lithography.
Mode-splitting in the FMR spectra has been investigated dependent on the size of the perturbations and compared to available analytical perturbation theory. Numerical simulations have been carried out to identify the spin waves corresponding to the mode spectra as well as to understand deviations between measurement and analytical theory for large perturbations.