Ferromagnetic resonance experiments of magnetic nanostructures over a large frequency range from $1\text{to}225\mathrm{GHz}$ are presented. We find unambiguous evidence for a nonlinear frequency dependence of the linewidth. The viscous Gilbert damping and two-magnon scattering are clearly separated. Both angular and frequency dependent measurements give a transverse scattering rate within the magnetic subsystem of the order of ${10}^9{\mathrm{s}}^{-1}$, whereas the longitudinal Gilbert relaxation into the thermal bath is one to two orders of magnitude smaller.

• Received 30 November 2005

DOI:https://doi.org/10.1103/PhysRevB.73.144424