Effective damping enhancement in noncollinear spin structures

TL;DR

This paper investigates how noncollinear spin arrangements in magnetic systems lead to an increased and mode-dependent effective damping of magnons, impacting the dynamics of skyrmions and related structures.

Contribution

It introduces a method to calculate the effective damping in noncollinear magnetic systems based on magnon polarization, extending understanding beyond traditional Gilbert damping.

Findings

Effective damping exceeds Gilbert damping in noncollinear systems.

Damping varies significantly between different excitation modes.

Numerical results for skyrmions in Pd/Fe/Ir(111) demonstrate the theory.

Abstract

Damping mechanisms in magnetic systems determine the lifetime, diffusion and transport properties of magnons, domain walls, magnetic vortices, and skyrmions. Based on the phenomenological Landau-Lifshitz-Gilbert equation, here the effective damping parameter in noncollinear magnetic systems is determined describing the linewidth in resonance experiments or the decay parameter in time-resolved measurements. It is shown how the effective damping can be calculated from the elliptic polarization of magnons, arising due to the noncollinear spin arrangement. It is concluded that the effective damping is larger than the Gilbert damping, and it may significantly differ between excitation modes. Numerical results for the effective damping are presented for the localized magnons in isolated skyrmions, with parameters based on the Pd/Fe/Ir(111) model-type system.