Triple and double hysteresis loops in relaxor ferroelectric PMN-0.28PT crystals

The evolution of the dielectric hysteresis loops shape during heating of PMN-0.28PT single crystals possessing rhombohedral symmetry at room temperature was studied in the temperature range from room temperature to 200 degrees C. Revealed formation of the triple and double dielectric hysteresis loops in the relaxor phase upon switching by an electric field was explained by the influence of depolarizing fields arising at the interface of non-polar inclusions, and by the ineffective screening of polar clusters forming during transition through a percolation threshold, correspondingly. Further size decrease in the polar clusters due to heating led to their transformation to polar nanoregions.