Interpretation of spin-wave modes in Co/Ag nanodot arrays probed by broadband ferromagnetic resonance

Ferromagnetic resonance (FMR) and the measurement of magnetization dynamics in general have become sophisticated tools for the study of magnetic systems at the nanoscale. In this work, we present a detailed investigation of Co/Ag nanodots with a 200 nm diameter arranged in a square pitch array with a periodicity of 400 nm, which, due to their size, can support standing spin-wave modes with complex spectral responses. To interpret the experimentally measured broadband FMR, we compare the spectra of the nanoarray structure with those of the unpatterned Co/Ag film of identical thickness, which serves as a baseline for obtaining the general magnetic parameters of the system. Using state-of-the-art simulations of the dynamic response to identify the nature of the excitation modes allows us to assess the boundary conditions for the nanodots. We then proceed to calculate the spectral response of our system, for which we obtained good agreement. A full description of the theoretical framework and its application to our system is provided and the novel frequency domain, matrix-free simulation method used is described in detail.