Aging and slow dynamics inSrxBa1−xNb2O6

Abstract

The uniaxial "relaxor" ferroelectric Sr x Ba 1−x Nb 2 O 6 ͑SBN͒ is found to crossover from holelike to cumulative aging as it is cooled into the frozen relaxor regime. The cumulative aging contrasts sharply with the behavior of cubic relaxors, supporting ideas that the spin-glasslike aging in cubic relaxors is connected with polarization components orthogonal to the net ferropolarization. In the relaxor regime, small dc fields are found to suppress much of the dissipative response, similar to long-time aging. Pyroelectric currents are measured, along with limits on pyroelectric noise, allowing limits to be set on dynamically coherent domain sizes. Large nonlinear susceptibilities are found near the freezing transition.

Investigation of the electrocaloric effect in a PbMg2/3Nb1/3O3-PbTiO3 relaxor thin film

“…4 literally, as relaxors are never formally in thermal equilibrium. 22,26,27 However, the FH data suggests the intriguing possibility of a large ⌬T =9 K at 25°C when E = 723 kV cm −1 is applied. This is an interesting outcome because no dielectric material has shown or been predicted to show such a large ECE at room temperature.…”

Field dependence of glassy freezing in a relaxor ferroelectric

“…In fact, for one such material T P shows no clear systematic decrease with polarization, i.e., C Ͻ 0.03. 8 In contrast we now have preliminary results on a plain PMN crystal which approximately fit the GT form with C about one.…”

“…Nevertheless, the strong GT-type sensitivity of T VF to polarization would be hard to understand unless, as in the spin-glass case, the polarizing entities are the same things whose interactions drive the formation of the glassy state. For example, the entities ͑probably unit-cell displacements orthogonal to PNR polarizations͒ 5,8 which contribute low-T spin-glass-like aging in polarized states well above the GT line 9 would be very unlikely candidates to show simple GT behavior with C of order unity.…”

“…Explanations for that kinetic freezing include simple growth of barriers as PNR grow in fixed random fields, 4 growth of kinetic barriers as PNR interact with a glass of interacting unit-cell displacements orthogonal to the PNR polarization, 5 and various forms of glass formed as a result of inter-PNR interactions. 6,7 We have presented considerable evidence that in perovskite relaxors ͑with an average cubic symmetry͒, unlike uniaxial relaxors, 8 a low-temperature spin glass is present even when the PNRs are too highly polarized to support any spin-glass order. 9 However, it has not been clear whether that result could be extrapolated to conclude that the kinetic effects causing the loss of susceptibility were due to those same unit-cell-scale degrees of freedom involved in the aging.…”

Phase transition of the uniaxial disordered ferroelectric Sr0.61Ba0.39Nb2O6

“…This polarization is however unusual in several aspects. The value of P s at saturation and the critical exponent β depend on how the poled state is prepared [7], [8]. Moreover, both rejuvenation and memory effects are observed in the ferroelectric state of SBN [7], [9].…”