Ferrroelectric phase transitions and the Ising model

Barreto, F. C. Sá

doi:10.1590/s0103-97332000000400027

Cited by 8 publications

(12 citation statements)

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“…We can conjecture that the mechanism that suppresses the phase transition may be connected to tunnelling of H 2 O molecules between the states in the six-well potential 43 44 . The ferroelectric phase transition may also be inhibited because the structural channels of the beryl crystal are not completely filled by water molecules; together with the weaker interaction among the H 2 O clusters in adjacent channels, this may prevent the formation of a macroscopically ordered state.…”

Section: Resultsmentioning

confidence: 99%

“…These can be the following: (i) the presence of impurities or defects, including the alkali ions; (ii) the presence of not only isolated dipoles (lone water molecules) but of doublets, triplets and so on that are randomly spread over the crystal; (iii) the quasi-1D character of the dipole arrangement and, correspondingly, certain distribution in the inter-dipole interaction strength within and across the channels, see Fig. 1c ; (iv) possible tunnelling between the potential minima that can act as a source of disorder and thus broaden the line 43 44 ; and (v) the temperature dependence of the shape and of the depth of the potential wells and/or of the mean-field coupling constant γ .…”

Section: Resultsmentioning

confidence: 99%

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Incipient ferroelectricity of water molecules confined to nano-channels of beryl

et al. 2016

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Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole–dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole–dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie–Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Incipient ferroelectricity of water molecules confined to nano-channels of beryl

et al. 2016

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“…The model exhibits ferroelectric behavior, with broad, hard hysteresis characteristics. By itself, the appearance of ferroelectricity in a system of interacting dipoles is not surprising; such ferroelectric behavior occurs in higher‐dimensional Lenz‐Ising models of dipolar systems and the present model can be viewed as a complicated version of a Lenz‐Ising model. What is of specific interest in the present polar polyethylene simulations is the time‐domain progression of polarization reversal response as a function of applied electric field and temperature, and the comparison and contrast to the initial polarization response.…”

Section: Resultsmentioning

confidence: 81%

“…Lenz-Ising models [56][57][58][59] of dipolar systems and the present model can be viewed as a complicated version of a Lenz-Ising model. What is of specific interest in the present polar polyethylene simulations is the time-domain progression of polarization reversal response as a function of applied electric field and temperature, and the comparison and contrast to the initial polarization response.…”

Section: Full Papermentioning

confidence: 99%

Molecular dynamic study of dielectric polarization and ferroelectricity in a model polar polymer

Calame

2015

J Polym Sci B Polym Phys

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Molecular dynamics simulations are used to explore the polarization response of a lamellar crystal consisting of folded chains of a highly simplified model polar polymer. The system is based on a united atom model of polyethylene with constrained bond lengths and bond angles, and it is endowed with artificial partial charges placed on the united atoms to give it a simple polar character. Simulations performed with various temperatures, electric field directions, and electric field application histories reveal a complicated sequence of reorientation processes, including pronounced ferroelectric behavior. The sequence includes a weak, temperature‐independent prompt response, and a slow‐rising delay regime with stretched exponential behavior and thermally‐activated reorientation parameters consistent with trans‐gauche (TG) barrier crossings in the amorphous phase. When the delay regime has progressed sufficiently, a primary large‐amplitude response due to organized rotation of large subsegments in the crystalline phase occurs in a rapid manner that requires relatively few TG barrier crossings. A final, extremely slow rise in residual polarization completes the sequence. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 740–759

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“…More specifically, the short-range interaction energy between local c-axisoriented moments D i in LiOsO 3 [ Fig. 1(a)] can be described by the thermal expectation value of an Ising-type Hamiltonian H int = i j J i j D i D j [6,9,16], where the coupling constants J i j depend sensitively on the position of atoms in the vicinity of sites i and j. The atomic positions minimize the total elastic with photon energyhω = 1.5 eV is focused onto the sample at some chosen angle of incidence θ i .…”

Section: Introductionmentioning

confidence: 99%

Evidence for an extended critical fluctuation region above the polar ordering transition in LiOsO3

Shan

Torre

Laurita

et al. 2020

Phys. Rev. Research

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Metallic LiOsO 3 undergoes a continuous ferroelectric-like structural phase transition below T c = 140 K to realize a polar metal. To understand the microscopic interactions that drive this transition, we study its critical behavior above T c via electromechanical coupling-distortions of the lattice induced by short-range dipoledipole correlations arising from Li off-center displacements. By mapping the full angular distribution of second harmonic electric-quadrupole radiation from LiOsO 3 and performing a simplified hyper-polarizable bond model analysis, we uncover subtle symmetry-preserving lattice distortions over a broad temperature range extending from T c up to around 230 K, characterized by nonuniform changes in the short and long Li-O bond lengths. Such an extended region of critical fluctuations may explain anomalous features reported in specific heat and Raman scattering data and suggests the presence of competing interactions that are not accounted for in existing theoretical treatments. More broadly, our results showcase how electromechanical effects serve as a probe of critical behavior near inversion symmetry-breaking transitions in metals.

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Ferrroelectric phase transitions and the Ising model

Cited by 8 publications

References 0 publications

Incipient ferroelectricity of water molecules confined to nano-channels of beryl

Incipient ferroelectricity of water molecules confined to nano-channels of beryl

Molecular dynamic study of dielectric polarization and ferroelectricity in a model polar polymer

Evidence for an extended critical fluctuation region above the polar ordering transition in LiOsO3

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