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Browsing by Author "Colla, Eugene V."

Now showing 1 - 6 of 6
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    Aging and slow dynamics in SrxBa1-xNb2O6
    Chao, L. K.; Colla, Eugene V.; Weissman, Michael B.; Viehland, Dwight D. (American Physical Society, 2005-10-10)
    The uniaxial "relaxor" ferroelectric SrxBa1-xNb2O6 (SBN) 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.
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    Bias-field effect on the temperature anomalies of dielectric permittivity in PbMg1/3Nb2/3O3-PbTiO3 single crystals
    Raevski, I. P.; Prosandeev, S. A.; Emelyanov, A. S.; Raevskaya, S. I.; Colla, Eugene V.; Viehland, Dwight D.; Kleemann, W.; Vakhrushev, S. B.; Dellis, J. L.; El Marssi, M.; Jastrabik, L. (American Physical Society, 2005-11-16)
    In contrast to ordinary ferroelectrics where the temperature T-m of the permittivity maximum monotonically increases with bias field E in (1-x)PbMg1/3Nb2/3O3-(x)PbTiO3 (0 <= x <= 0.35) single crystals, T-m was found to remain constant or to decrease with E up to a certain threshold field E-t, above which T-m starts increasing. The threshold field E-t decreases with increasing x, tending toward zero at approximately x=0.4. We explain this dependence in the framework of models which take into account quenched random fields and random bonds. For crystals with 0.06 <= x <= 0.13, the E-T phase diagrams are constructed. In contrast to PMN, they exhibit an additional, nearly field-independent boundary, in the vicinity of the Vogel-Fulcher temperature. We believe this boundary to correspond to an additional phase transition and the appearing order parameter is likely to be nonpolar.
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    Domain structure changes in (1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) with composition, dc bias, and ac field
    Viehland, Dwight D.; Li, Jiefang; Colla, Eugene V. (American Institute of Physics, 2004-09-15)
    Domain structure changes in (1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) have been studied by polarized optical microscopy. In the zero-field-cooled condition, increasing the x revealed systematic changes in the domain morphology from polar nanodomains for x<0.25, to fine crosshatched domains near the morphotrophic phase boundary (MPB), and to micro-sized domains for x=0.4. In the vicinity of the MPB, an applied dc electrical bias resulted in a change of morphology from fine crosshatched (rhombohedral phase) to thin-aligned striationlike (monoclinic phase) domains. The application of an ac electric field to the crosshatched domains resulted in irregular domain wall oscillations/relaxations and increased nonuniformity. (C) 2004 American Institute of Physics.
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    Field dependence of glassy freezing in a relaxor ferroelectric
    Delgado, Miguel; Colla, Eugene V.; Griffin, P.; Weissman, Michael B.; Viehland, Dwight D. (American Physical Society, 2009-04-23)
    Multifrequency susceptibility measurements on the perovskite relaxor ferroelectric (PbMg(1/3)Nb(2/3)O(3))(0.88)(PbTiO(3))(0.12) were performed at various strengths of dc electric field applied along the [111] direction. The temperature-frequency dependences fit the Vogel-Fulcher form, allowing the extraction of a frequency-independent glassy freezing temperature. These Vogel-Fulcher temperatures showed significant reductions in applied fields, following an empirical Gabay-Toulouse form, similar to vector spin glasses. The magnitude of the sensitivity indicates that the glassy state is formed by interactions among the same entities which account for the susceptibility, i.e., the polar nanoregions. That interpretation is supported by other data showing a loss of Vogel-Fulcher behavior in a powder sample of PbMg(1/3)Nb(2/3)O(3), with grains too small to support large-scale internanoregion cooperativity.
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    Kinetics and thermodynamics of the ferroelectric transitions in PbMg1/3Nb2/3O3 and PbMg1/3Nb2/3O3-12% PbTiO3 crystals
    Colla, Eugene V.; Jurik, Nathan; Liu, Yehan; Delgado, Miguel; Weissman, Michael B.; Viehland, Dwight D.; Ye, Zuo-Guang (American Institute of Physics, 2013-05-14)
    The two-step freezing and melting of the field-induced ferroelectric order in PbMg1/3Nb2/3O3 (PMN) and (PbMg1/3Nb2/3O3)(0.88)(PbTiO3)(0.12) (PMN-PT) is investigated. In PMN-PT, direct microscopic images show that both steps occur in the same spatial regions. The higher temperature freezing corresponds to the higher temperature melting, indicating that the stages are not just kinetically but also thermodynamically distinct. The higher-T melting step shows several indications of being a sharp first-order transition near an equilibrium temperature. The lower-T melting step shows more kinetic dependence. Partially poled PMN also spontaneously approaches saturation polarization on zero-field aging, indicating that the true equilibrium state is ferroelectric below similar to 200 K. In PMN-PT, a variety of kinetic measurements on the ferroelectric state indicate that the kinetics are governed by a glassy matrix showing aging effects. (C) 2013 AIP Publishing LLC.
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    Stability of glassy and ferroelectric states in the relaxors PbMg1/3Nb2/3O3 and PbMg1/3Nb2/3O3-12% PbTiO3
    Colla, Eugene V.; Vigil, D.; Timmerwilke, J.; Weissman, Michael B.; Viehland, Dwight D.; Dkhil, B. (American Physical Society, 2007-06-05)
    The stability of the disordered glassy phase in the relaxors PbMg1/3Nb2/3O3 and (PbMg1/3Nb2/3O3)(0.88)(PbTiO3)(0.12), called PMN and PMN-PT, was investigated by preparing partially polarized samples and allowing them to age at zero field in the temperature range for which the phase is history dependent. The PMN-PT polarization would spontaneously increase until long-range order formed, first appearing as giant polarization noise. Thus, the thermodynamically stable phase in PMN-PT appears to be ferroelectric. In contrast, a PMN sample lacking the sharp first-order field-driven transition found in some other samples spontaneously depolarized, consistent with its glassy state being thermodynamically stable. Detailed thermal depolarization results in PMN showing two distinct broad peaks, as well as a small fraction of material with a distribution of abrupt melting transitions.