Local spin-wave dispersion and damping in thin yttrium-iron-garnet films

Rouven Dreyer, Niklas Liebing, Eric R. J. Edwards, Georg Woltersdorf

Published 2018-03-13Version 1

Using ultrafast magneto-optic sampling microscopy, we investigate the spin-wave dispersion and spin-wave damping in yttrium-iron-garnet films. With the aid of the inhomogeneous magnetic field generated by coplanar waveguides spin-waves are excited at a fixed frequency while the wavelength is determined by the external magnetic field. By imaging the excited spin-waves and mapping the dispersion we identify a method to determine the damping of the uniform mode locally. The group velocity approaches zero in the vicinity of an avoided crossing of different spin-wave modes. A local Gilbert damping parameter is extracted for spin-waves with finite wave vector and the result is in good agreement with the local measurement for the uniform mode. Resonance linewidths are much narrower compared to inductive ferromagnetic resonance measurements performed on the same sample indicating that in the linewidth is limited by inhomogeneous properties in the inductive measurement.