Percolation model for relaxation in random systems

We have measured the magnetic relaxation of several Au:Fe alloys from ${10}^{\mathrm{-}5}$ to ${10}^4$ sec after removing an applied field. The quality and range of the data are sufficient to demonstrate significant deviations from all functions previously used to characterize the dynamics of similar systems. A simple model, activated relaxation of dispersive excitations on a percolation distribution of finite-sized domains, gives excellent agreement with the measurements and may provide a common link between fundamental excitations and observed behavior in random systems.