Order and disorder at the improper ferroelectric transition of chromium-chlorine boracite

Lockwood, D. J.

doi:10.1080/00150198108218149

Cited by 6 publications

(2 citation statements)

References 9 publications

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“…It is therefore possible that the mechanism is of order/disorder rather than displacive character. Issues of displacive and order/disorder contributions (eg in references [30,31]) can be tested at the simplest phenomenological level by comparison of Landau and Bragg-Williams solutions for the temperature dependence of the order parameter, q. As set out in the appendix, neither of the standard Landau solution for a weakly first order transition, representing a displacive limit, or the standard Bragg-Williams solution [32], representing an order/disorder limit, reproduces the temperature dependence of q 2 .…”

Section: Order/disorder Character and Strain Couplingmentioning

confidence: 99%

Order–disorder, ferroelasticity and mobility of domain walls in multiferroic Cu–Cl boracite

Fernández-Posada

Cochard

Gregg

et al. 2020

J. Phys.: Condens. Matter

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Domain walls in Cu–Cl boracite develop as a consequence of an improper ferroelastic, improper ferroelectric transition, and have attracted close interest because some are conductive and all can be mechanically written and repositioned by application of an electric field. The phase transition and its associated dynamical properties have been analysed here from the perspective of strain and elasticity. Determination of spontaneous strains from published lattice parameter data has allowed the equilibrium long-range order parameter for F 4 ̄ 3c → Pca21 to be modelled simply as being close to the order–disorder limit. High acoustic loss in the cubic phase, revealed by resonant ultrasound spectroscopy, is consistent with the presence of dynamical microdomains of the orthorhombic structure with relaxation times in the vicinity of ∼10−5–10−6 s. Low acoustic loss in the stability field of the orthorhombic structure signifies, on the other hand, that ferroelastic twin walls which develop as a consequence of the order–disorder process are immobile on this time scale. A Debye loss peak accompanied by ∼1% elastic stiffening at ∼40 K is indicative of some freezing of defects which couple with strain or of some more intrinsic freezing process. The activation energy of ⩾∼0.01–0.02 eV implies a mechanism which could involve strain relaxation clouds around local ferroelectric dipoles or freezing of polarons that determine the conductivity of twin walls.

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Section: Order/disorder Character and Strain Couplingmentioning

confidence: 99%

Order–disorder, ferroelasticity and mobility of domain walls in multiferroic Cu–Cl boracite

Fernández-Posada

Cochard

Gregg

et al. 2020

J. Phys.: Condens. Matter

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show abstract

“…Many of the boracites show ferroelectric properties [13] and some Raman studies have been undertaken to determine the ferroelectric phase transitions [14][15][16]. Vibrational spectroscopy has focussed on the ferroelectric transitions [17][18][19][20][21][22][23][24]. Different types of boracites have been synthesised [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Assessment of the molecular structure of the borate mineral boracite Mg3B7O13Cl using vibrational spectroscopy

Frost¹,

Xi²,

Scholz³

2012

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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7.2.9 Dielectric and related properties

Burzo¹

Landolt-Börnstein - Group III Condensed Matter

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Order and disorder at the improper ferroelectric transition of chromium-chlorine boracite

Cited by 6 publications

References 9 publications

Order–disorder, ferroelasticity and mobility of domain walls in multiferroic Cu–Cl boracite

Order–disorder, ferroelasticity and mobility of domain walls in multiferroic Cu–Cl boracite

Assessment of the molecular structure of the borate mineral boracite Mg3B7O13Cl using vibrational spectroscopy

7.2.9 Dielectric and related properties

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