Relaxational dynamics of polar nanodomains in Sr
 
 1 −
 x
 
 Ca
 
 x
 
 TiO
 3
 x
 = 0.002

Kleemann, W.; Albertini, A; Chamberlin, Ralph V.; Bednorz, J. G.

doi:10.1209/epl/i1997-00124-7

Cited by 33 publications

(23 citation statements)

References 19 publications

(50 reference statements)

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“…However, there is evidence from computer simulation studies dealing with spin glasses [4] suggesting that dynamic heterogeneity may also be found in crystalline substances. In fact, models consistent with the existence of dynamic heterogeneity have been successful in describing the polydispersive dielectric response of multidomain ferroelectrics [5].In this Letter we report direct experimental evidence for dynamic heterogeneity in a relaxor ferroelectric, i.e., in a crystal, via the technique of dielectric nonresonant spectral hole burning (NHB). This method is based on a pump, wait, and probe scheme [6].…”

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Long-Lived Dynamic Heterogeneity in a Relaxor Ferroelectric

1998

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The polydispersive dielectric response of the relaxor ferroelectric lead magnesium niobate was investigated using nonresonant spectral hole-burning experiments. Using large alternating electric fields, specific parts of the relaxation-time distribution could be addressed selectively. This provides evidence for the dynamic heterogeneity of the dipolar reorientation process. The refilling of single as well as of double holes was much slower than the time scale set by the pump frequencies. Upon refilling, the holes exhibited no signs of spectral broadening. The present findings suggest a speedup of polarization response associated with a domain-wall depinning that is induced by the hole-burning event.[S0031-9007(98)07584-X] PACS numbers: 77.84.Dy, 77.22.Ej, The relaxation of disordered and glass-forming materials was often pictured as being due to independently responding nanoregions. Only recently this notion could be substantiated experimentally for supercooled liquids and polymers [1,2]. Above the glass transition the time scale characterizing this heterogeneity was found to be very close to that of the structural relaxation itself. Thus the heterogeneity, which gives rise to the ubiquitously observed broadening of susceptibility spectra here, is dynamic in nature. This may have been expected since the notion of a static heterogeneity is incompatible with the concept of a metastable ergodic liquid state. On the other hand, in polar, disordered crystals, such as relaxor ferroelectrics (RF), transmission electron microscopy has revealed clear evidence for nanoscale ͑ϳ5 nm͒ heterogeneity [3]. It arises from local fluctuations in the chemical composition of these highly polar materials, and typically is quasistatic near and below room temperature. However, there is evidence from computer simulation studies dealing with spin glasses [4] suggesting that dynamic heterogeneity may also be found in crystalline substances. In fact, models consistent with the existence of dynamic heterogeneity have been successful in describing the polydispersive dielectric response of multidomain ferroelectrics [5].In this Letter we report direct experimental evidence for dynamic heterogeneity in a relaxor ferroelectric, i.e., in a crystal, via the technique of dielectric nonresonant spectral hole burning (NHB). This method is based on a pump, wait, and probe scheme [6]. In contrast to NHB results previously obtained for supercooled liquids, we find that in RF the hole refilling proceeds slow on the time scale that governs the dynamics of the mesoscopic regions addressed during the frequency-selective pump. Obviously, the existence of well-established static heterogeneities in RF promotes the slowdown of spectral reequilibration.For our studies we have used PbMg 1͞3 Nb 2͞3 O 3 (PMN) ceramics doped with 10% PbTiO 3 (90PMN-10PT) which has been found to be much less susceptible to chemical aging than "pure" PMN [3]. PMN is one of the prototypic relaxors [3], and the polydispersive complex dielectric constant of this material has been document...

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Long-Lived Dynamic Heterogeneity in a Relaxor Ferroelectric

1998

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“…[47] and references therein). It was suggested in GOies that the phase transition from the paraelectric to ferroelectric A, for Nb <100> displacements -Linear fit of Ĉ oncentration of Nb, in at.…”

Section: Development Of the Microscopic Functional For The Excess mentioning

confidence: 99%

Large-scale quantum chemical modeling of the phase transitions in KTN solid solutions

Eglitis¹,

Fuks²,

Dorfman³

et al. 2003

AIP Conference Proceedings

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Self-ordered second-component clusters in solid solutions on the basis of ferroelectric perovskites: Nb clusters in KTaO 3 AIP Conf.Abstract. The large-scale modeling of the atomic and electronic structure of KNb^Tai-ajOa (KTN) perovskite solid solutions is performed using the Intermediate Neglect of the Differential Overlap (INDO) method based on the Hartree-Fock formalism. It is found that periodic Nb impurities in KTaOs reveal coherent off-center displacements already at the smallest calculated concentration, or-0.125. The calculated magnitude of < 111 > Nb off-center displacement is 0.27 a.u., which is close to the XAFS observation at 70 K and #=0.09. In contrast, Ta impurities in KNbOa remain on-center, due to higher ionicity of Ta, as compared to Nb. Using the calculated energy gain caused by the off-center displacements of Nb atoms, the non-empirical Ginzburg-Landau-Devonshire functional with concentration-dependent coefficients is constructed. Analysis of INDO results for several Nb concentrations in KTN allows calculate the lowest critical Nb concentration, # cr =0.025, corresponding to the quantum displacive limit for the paraelectric-ferroelectric transition at 0 K. This value is only slightly higher than the experimental one.

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“…This crystal does not experience the ferroelectric phase transition [5]. Stability of paraelectric phase comes from the appearance of the quantum effect of the fluctuations [6][7][8][9][10][11][12][13][14]. It is possible, that the small amount of dopant (Li + or Nb + ) or intrinsic imperfection of the crystal through elastic interactions can lead to local glass-like short-range order or even ferroelectric long-range order.…”

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K_0.9982Li_0.0018TaO₃Crystal Under External DC Electric Field

et al. 2012

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The influence of external dc electric field on dielectric properties of K 1-x Li x TaO 3 x = 0.18% (henceforth KLT-x%) is presented. Electric permittivity dependence on dc electric field confirms the existence of short-range electric order. According to the suggestion made by us [1] the substitution of K + ions by off-center Li + in KTaO 3 is considered as the source of induced polar clusters of short range order at low temperatures for this crystal. The low-temperature state of KLT-0.18 may be considered as a quantum superparaelectric one that may be toggled into an improper ferroelectric while applying an electric field [2] or a chiral glass state [3].

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Relaxational dynamics of polar nanodomains in Sr _{1 −
x} Ca _x TiO ₃ x = 0.002

Cited by 33 publications

References 19 publications

Long-Lived Dynamic Heterogeneity in a Relaxor Ferroelectric

Long-Lived Dynamic Heterogeneity in a Relaxor Ferroelectric

Large-scale quantum chemical modeling of the phase transitions in KTN solid solutions

K_0.9982Li_0.0018TaO₃Crystal Under External DC Electric Field

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Relaxational dynamics of polar nanodomains in Sr 1 − x Ca x TiO 3 x = 0.002

Cited by 33 publications

References 19 publications

Long-Lived Dynamic Heterogeneity in a Relaxor Ferroelectric

Long-Lived Dynamic Heterogeneity in a Relaxor Ferroelectric

Large-scale quantum chemical modeling of the phase transitions in KTN solid solutions

K0.9982Li0.0018TaO3Crystal Under External DC Electric Field

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Relaxational dynamics of polar nanodomains in Sr _{1 −
x} Ca _x TiO ₃ x = 0.002

K_0.9982Li_0.0018TaO₃Crystal Under External DC Electric Field