Abstract The relaxation of magnetostatic spin waves in a square NiFe nano-element (100×100×20 nm3) has been simulated by micromagnetic finite element modeling after the excitation by a rotational field of μ0H=0.2 T with various frequencies between 1 and 16 GHz. The micromagnetic simulations are based on the Landau–Lifshitz–Gilbert equation of motion with a Gilbert damping parameter α=0.02. The relaxation after switching off the external field led to a damped oscillation of the magnetization, which is related to changes of the exchange and magnetostatic field energies of the system. Finally, depending on the frequency of the rotating field “C-” and “S-” domain configurations were observed after approximately 10 ns. The different inhomogeneous magnetostatic and exchange field strength values inside the square for the “C-” and “S-” state lead to different frequencies of the magnetostatic spin-wave modes, such as about 4.5 GHz for the C-state and 3 GHz for the S-state, respectively.