Micromagnetic Simulation of Ferromagnetic Resonance in a Nanosized Bilayer Exchange-Coupled Square-Shaped Ferromagnetic Film.

A numerical method for computing ferromagnetic resonance (FMR) is adapted for a confined bilayer exchange-coupled film. In this method, the system is unbalanced from the equilibrium by a short weak external magnetic field, and then the OOMMF micromagnetic simulation package is used to simulate the system's return to equilibrium and to record the resulting magnetization dynamics. After performing the Fourier transform of the time series of magnetization variation, the frequency dependences of the spectral density are calculated. The resonance frequencies are determined by correlating the maxima of these dependences with their corresponding frequencies. The study concerns the main modes and corresponding distributions of magnetization excitation in films of varying sizes when the constant magnetic field changes from saturating to zero. The FMR has been investigated, specifically, for the earlier studied vortex distribution of magnetization in the normal state. It is shown that the transition of the main mode to the low-frequency region occurs when the intensity of the external magnetic field decreases. This technique can be used to analyze the dynamic properties of multiferroic heterostructures in the future. [ABSTRACT FROM AUTHOR]