On the kinetics of slow polarization in the lead magnoniobate ferroelectric relaxor

Polarization and repolarization of a (100)-oriented lead magnoniobate crystal in slowly varying and dc electric fields were measured in a temperature interval including the relaxor and field-induced ferroelectric states. Throughout the interval covered, the polarization was shown to exhibit features characteristic of relaxors, namely, open, nonreproducing polarization trajectories in the first few cycles of quasistatic dielectric hysteresis loops and very long relaxation times. The slow thermally activated relaxation stage follows the universal power law evolution, which permits one to determine possible simple spectra of the relaxation time distribution. Temperature dependences of some relaxation and spectral parameters were derived, and their differences in the relaxor and ferroelectric phases are discussed.