Polarization switching and long-time relaxation effects induced by off-center ions in KTa/sub 1-x/Nb/sub x/O/sub 3/

A striking anomaly was observed in the behavior of KTN (KTa/sub 1-x/Nb/sub x/O/sub 3/), namely, the appearance of a remanent polarization well above T/sub c/. Hysteresis loops were measured at different frequencies in a 3% KTN crystal. The shape of the loop changed significantly with frequency, a behavior that is due to the slow relaxation of randomly distributed off-center Nb ions interacting in clusters. A model of this relaxation is developed, and hysteresis loops are calculated which are in good agreement with experiment.<
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