Polarization changes in the ferroelectric relaxor lead magnesium niobate

A study is reported of the polarization and depolarization processes in the model ferroelectric relaxer, lead magnesium niobate (PMN), in pulsed and sine electric fields applied along the pseudocubic direction (001) above T-d (T-d is the phase transition temperature between the induced macrodomain ferroelectric and the nonpolar phases). The study was made by the electroluminescence and polarization-switching current hysteresis techniques. Pulsed electric-field measurements revealed the influence of pulse duration on electroluminescence intensity under polarization and depolarization of a sample, as well as a decrease of delay in the onset of depolarization for pulses shorter than the time required for the polarization to set in. A delay of depolarization in a sine electric field was observed to exist within a certain instantaneous field-strength interval. A study has also been made of the increase of the depolarization delay induced by simultaneous application of a sine electric field and a de bias, or of;ln axial mechanical stress varying in phase with the electric field. The results obtained indicate the onset and persistence of held-induced local ferroelectric regions within a certain interval of instantaneous electric-field strengths. The effect of domain and domain-like processes on these phenomena is discussed.