New measurements of the ac susceptibility in zero field for a (${\mathrm{Eu}}_{0.2}$${\mathrm{Sr}}_{0.8}$)S single crystal are reported. For the first time in a spin-glass we can resolve the frequency dependence of the inphase component ${\chi }^{\prime }$ (dispersion) as well as the out-of-phase component ${\chi }^{\prime \prime }$ (absorption). From these studies a clear change in the dynamic behavior of the system around the freezing temperature is found, which can be related to large ferromagnetic clusters. The susceptibility behavior is described in terms of a wide distribution of relaxation times characterizing the intercluster interactions.

• Received 3 January 1983

DOI:https://doi.org/10.1103/PhysRevB.27.3100