Lifetime and mean free path of spin waves in ultrathin cobalt films

Miniaturization of magnon-based devices into the nanometer range would require the utilization of exchange-dominated spin waves of nanometer wavelength. In experiment and theory we show that the intrinsic lifetime and mean free path of the homogeneous acoustic spin wave in ultrathin cobalt films is sufficiently long for such applications provided that the films are atomically flat. The presence of surface steps, however, shortens lifetime and mean free path. The experimental data are consistent with a model which assumes that steps act as perfect sinks for spin waves.