Dynamic response of polar nanoregions under an electric field in a paraelectric KTa(0.61)Nb(0.39)O(3) single crystal near the para-ferroelectric phase boundary

The dynamic response of polar nanoregions under an AC electric field was investigated by measuring the frequency dependence of the quadratic electro-optic (QEO) effect in a paraelectric KTa(0.61)Nb(0.39)O(3) single crystal near the para-ferroelectric phase boundary (0 °C < T-T(c) < 13 °C). The QEO coefficient R(11) − R(12) reached values as large as 5.96 × 10(−15) m(2)/V(2) at low frequency (500 Hz) and gradually decreased to a nearly stable value as the frequency increased to 300 kHz. Furthermore, a distortion of the QEO effect was observed at low frequency and gradually disappeared as R(11) − R(12) tended towards stability. The giant QEO effect in the KTa(0.61)Nb(0.39)O(3) crystal was attributed to the dynamic rearrangement of polar nanoregions and its anomalous distortion can be explained by considering the asymmetric distribution of polar nanoregions.