Complex dynamics of self-generated magnetic clusters in phase-separated perovskites

The linear and non-linear AC magnetic susceptibilities of the perovskite La1−xSrxCoO3, with 0.15⩽x⩽0.30, are presented. It is observed that, for x<0.20, a freezing temperature is defined by AC magnetic susceptibility, pointing to a glassy behaviour whose origin is the phase separation of ferromagnetic metallic-like clusters embedded in an insulating matrix. At this temperature, the non-linear magnetic susceptibility shows critical divergence, similar to spin-glasses, although the width of the diverging peak does not compare well with canonical spin-glasses.