Nonlinear domain wall resonance in garnet films with perpendicular anisotropy: Critical role of nonlinear damping

Abstract

International audienceDomain wall resonance spectra in the weakly nonlinear regime for garnet films with a perpendicular anisotropy supporting parallel stripe domains have been investigated using micromagnetic simulations and zero-field broadband ferromagnetic resonance experiments. The main characteristics of the 2D numerical micromagnetic approach we developed is to solve the Landau-Lifshitz equation by an iterative method in the frequency domain and to incorporate a nonlinear phenomenological damping term. It is shown that the nonlinear damping affects simultaneously the driving field dependencies of the resonance frequency and the resonance linewidth for the fundamental domain wall resonance of parallel stripe domains, and the critical field for the domain wall resonance foldover. The micromagnetic simulations allow us to reproduce quantitatively both the nonlinear redshift of the domain wall resonance frequency and the nonlinear line broadening experimentally observed for increasing values of the input microwave power

Nonlinear Collective Excitations for a Periodic Array of Domain Walls in Garnet Films with Perpendicular Anisotropy

“…For P=200 mW, the resonance linewidth is enhanced by a factor 1.8 with respect to the linear regime. Such power evolutions have been previously reported and nicely reproduced by micromagnetic simulations including a nonlinear damping parameter [9] for a sample with similar magnetic parameters except a sligthly larger value of the saturation magnetization. (iii) The power absorption at resonance first increases rapidly with P and then saturates at P s = 50 mW (Fig.…”

“…These effects have been experimentally observed both for the domain mode resonances [7] and for the lowest-frequency DW mode resonance [8,9]. In addition, it has been recently shown that a correct description of the power dependences of the resonance shift and the line broadening in a phenomenological approach requires to take into account a nonlinear damping parameter [7,9]. Further increasing the amplitude of the pumping field results in a possible parametric excitation of DW waves with k 0 through a three-DW-wave interaction mechanism (equivalent to the first-order Suhl instability for the ferromagnetic resonance (FMR) [10]) or a four-DW-wave interaction process (second-order Suhl instability for the FMR [10]) as theoretically analyzed [11] and revealed using a magneto-optic detection [12].…”

“…Restricting to the domain mode resonances and the translational DW resonances, the lowest-order nonlinear process takes place in the weakly nonlinear regime characterized by a frequency shift (redshift) of the resonance lines accompanied with an asymmetric line broadening. These effects have been experimentally observed both for the domain mode resonances [7] and for the lowest-frequency DW mode resonance [8,9]. In addition, it has been recently shown that a correct description of the power dependences of the resonance shift and the line broadening in a phenomenological approach requires to take into account a nonlinear damping parameter [7,9].…”