Two-Dimensional Ising Model Criticality in a Three-Dimensional Uniaxial Relaxor Ferroelectric with Frozen Polar Nanoregions

Abstract

The charge-disordered three-dimensional uniaxial relaxor ferroelectric Sr0.61Ba0.39Nb2O6 splits up into metastable polar nanoregions and paraelectric interfaces upon cooling from above Tc. The frozen polar nanoregions are verified by piezoresponse force microscopy, respond domainlike to dynamic light scattering and dielectric excitation, reveal nonergodicity at T>Tc via global aging, and coalesce into polar nanodomains below Tc. Contrastingly, the percolating system of unperturbed interfaces becomes ferroelectric with two-dimensional Ising-model-like critical exponents alpha=0, beta=1/8, and gamma=7/4, as corroborated by ac calorimetry, second harmonic generation, and susceptometry, respectively.

Intrinsic and extrinsic central peaks in the Brillouin light scattering spectrum of the uniaxial ferroelectric relaxor Sr0.61Ba0.39Nb2O6

“…Owing to the uniaxial nature of the order parameter and the existence of random fields, the diffuse phase transition of SBN-61 has been interpreted in the framework of a three-dimensional random-field Ising model. 3 The formation of polar nanoregions ͑PNRs͒ at a certain temperature, the so-called Burns temperature ͑T B ͒, has been suggested as a common feature of ferroelectric relaxors. The existence of PNRs has been indicated by unusual properties such as deviations of the index of refraction and the strain from high-temperature linearities, 4-6 appearance of diffuse neutron scattering, 7 quasielastic central peaks ͑CPs͒ observed in the light scattering spectrum, 8 etc.…”

Mapping bias-induced phase stability and random fields in relaxor ferroelectrics

“…4 The development of piezoresponse force microscopy ͑PFM͒ in the past decade has precipitated several studies of mesoscopic domain polarization distributions in relaxor ferroelectrics, including observations of fractal domain walls in the nonergodic phase of relaxors, [5][6][7] ferroelectric domains in uniaxial relaxors, 8,9 and persistent labyrinthine domains of spontaneous polarization in the macroscopically nonpolar "ergodic" relaxor phase. 6,10,11 Complementary to imaging static domain patterns, piezoresponse force spectroscopy 12 was used to study local polarization dynamics in relaxors. 6 These experiments are analogous to macroscopic bias-induced experiments, allowing the phase-field diagram of relaxor ferroelectrics to be sampled locally.…”

Structural Transformations in Ferroelectrics Discovered by Raman Spectroscopy

“…Recently, bismuth layer-structured ferroelectrics (BLSFs) have gained increasing attention for the promising applications of non-volatile random access memories (NvRAMs), optical switches and high-temperature piezoelectric devices, because of their relatively high T c , low dielectric dissipation, and excellent hysteresis behavior [22][23][24][25]. Calcium bismuth niobate (CaBi 2 NbO 9 , CBN) is an Aurivillius layered material with the ultra-high T c and relative higher thermal depoling temperature.…”