Field dependence of spin excitations in NiFe/Cu/NiFe trilayered circular dots

Brillouin light scattering has been exploited to study the magnetic normal modes of trilayered circular dots (radius 100 nm), consisting of a pair of 10 nm thick permalloy layers separated by a Cu spacer with thickness of 10 nm. The field evolution of both the frequencies and the profiles of the spin-wave modes was investigated over a wide range of applied fields, encompassing both the parallel alignment of the layers magnetizations at saturation and the in-plane antiparallel state at remanence. The experimental data have been satisfactorily reproduced using a micromagnetic approach which solves the discretized Landau-Lifshitz-Gilbert equation over the layered structure in the time domain and then performs a local Fourier transform.