Splitting of Ferromagnetic Resonance Spectra in Periodically Modulated 1-D Magnonic Crystal

In this paper, we present a systematic study of a series of 1-D magnonic crystals defined as periodic arrays of grooves in a Permalloy thin film. Thin films of Ni
₈₀
Fe
₂₀
with dimensions 350 μm by 10 μm and thickness 40 nm were prepared on the top of signal line of coplanar waveguides by a combination of photolithography, e-beam lithography and lift-off processing. Starting from thin films, stripe-type periodic structures (grooves) with a depth of 4 nm were created in a controlled manner by focused ion beam. By changing the dimensions of the distance between the grooves, it was possible to systematically tune single, double, triple, and quadruple ferromagnetic resonance (FMR) absorption modes. Broadband FMR experiments were carried out to collect the frequency and field-dependent FMR spectra. The experimental results are corroborated with micromagnetic simulations.