Frequency dependence of aging, rejuvenation and memory in a disordered ferroelectric

We characterize in details the aging properties of the ferroelectric phase of KTa1-xNbx O-3 (KTN), where both rejuvenation and (partial) memory are ob served. In particular, we carefully examine the frequency dependence of sev eral quantities that characterize aging, rejuvenation and memory. We find a marked subaging behaviour, with an a.c. dielectric susceptiblity scaling a s w roott(w) where t(w) is the waiting time. We suggest an interpretation i n terms of pinned domain walls, much along the lines proposed for aging in a disordered ferromagnet, where both domain wall reconformations and overal l (cumulative) domain growth are needed to rationalize the experimental fin dings.