American Physical Society, Physical review B, 18(76)
DOI: 10.1103/physrevb.76.184116
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Relaxor behavior induced by hydrostatic pressure up to 0.95GPa in the Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-30PT) ferroelectric crystal was studied using dielectric spectroscopy. With increasing pressure we observed the decrease of the ferroelectric phase transition temperature (TC) , the suppression and smearing of the dielectric anomaly at TC , and the appearance of strong relaxorlike dielectric dispersion below the temperature of the permittivity maximum (Tm) . Such kinds of pressure-induced alteration are inherent in compositionally disordered perovskite ferroelectrics. It is usually believed to signify a crossover from the ferroelectric ground state to the nonergodic relaxor ground state in which the dipole moments of polar nanoregions (PNRs) are frozen in a way characteristic of dipole glasses. Surprisingly, our analysis of the dielectric spectra in PMN-30PT at high pressure did not reveal any glassy freezing of dipole dynamics. This means that the nature of the high-pressure-induced ground state is different from the nonergodic relaxor state observed in canonical relaxors at ambient pressure. At T>TC the dielectric spectra measured in PMN-30PT under different pressures are qualitatively similar. They are composed of two contributions that follow the Kohlrausch-Williams-Watts (KWW) and the Curie-von Schweidler (CS) relaxation patterns, respectively. The dielectric susceptibility related to the KWW relaxation provides the major contribution to the total dielectric constant. The shapes of the frequency and temperature dependences of this susceptibility remain practically unaffected by pressure. Contrary to the canonical relaxors the KWW relaxation time does not obey the Vogel-Fulcher law. On the other hand the CS-related susceptibility, which is significant only at low frequencies, considerably increases with increasing pressure and the shapes of its frequency and temperature dependences change radically. At T