Numerical Ferromagnetic Resonance Experiments in Nanosized Elements

In this letter, we present a numerical approach to obtain the ferromagnetic resonance spectra of micrometer- and nanometer-sized magnetic elements by micromagnetic simulations. By mimicking common experimental conditions, we applied a static magnetic field and used a linearly polarized oscillating magnetic field to excite magnetization dynamics. A continuous single-frequency excitation is utilized, which permits the study of the steady-state dynamics in the space and time domain. This gives direct access to resonance fields, linewidths, and relative amplitudes as observed in the experiments, which is not easily accessible in pulsed schemes and allows for a one-to-one identification between simulation and experiment. Similar to numerical approaches using pulsed excitations, the phases, ellipticity, and spatial mode profiles of the spin-wave excitations may also be accessed. Using large excitation powers, we then showcase that one can additionally study nonlinear responses by this method, such as the nonlinear shift of the resonance fields and the foldover of the absorption lines. Since the dynamic susceptibility is directly determined from standard outputs of common micromagnetic codes, the presented method is robust, efficient, and easy-to-use, adding to its practical importance.