Spin-wave resonances of ferromagnetic films with spatially modulated anisotropy

We study the dynamical properties of a magnetic film with spatially modulated perpendicular anisotropy by numerical simulations. Both topologically charged states (magnetic skyrmions) and uncharged uniform and nonuniform states are considered. The dependences of the ferromagnetic resonance (FMR) spectra on the geometry and material parameters of the system are analyzed. It is found that the spectra contain resonances of the localized and delocalized modes of the magnetization oscillations. In the case of nonuniform states the localized modes have the form of rotating magnetization distributions. The direction of the rotation depends on the local density of the toroidal moment of the state. The magnetic states with different FMR spectra can be easily switched by a temporary applying of a uniform external magnetic field that can be used in the tunable microwave devices.