Giant nonlocal damping by spin-wave emission: Micromagnetic simulations

Abstract

A micromagnetic simulation scheme is employed to evaluate the damping processes occurring in all-optical pump-probe experiments. We reveal that small wavelength and high-energy, nanometer-sized domains form during the first stage of the relaxation process. The emission of spin waves propagating out of the excitation spot area dominates the energy dissipation process. This process becomes dominant for small excitation spot areas and increases the macroscopically observed damping constant $\ensuremath{\alpha}$ drastically. We find that the damping time can be increased by a factor of more than 100, depending on the geometry, and must be considered in the interpretation of all-optical pump probe experiments with spot diameters less than $1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$.