Structural phase transition induced by elastic fields of impurities

Glinchuk, M. D.; Smolyaninov, I. M.

doi:10.1080/01411599008207946

Cited by 7 publications

(3 citation statements)

References 14 publications

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“…Indeed, the coupling between a quadrupole at a K site and an ordered array of quadrupoles is allowed by symmetry, in contrast with the dipole analogue. As in the latticedynamical model, only detailed knowledge of the interaction forces allows one to judge whether this approach predicts condensation into an ordered or disordered state (see also Glinchuk and Smolyaninov (1990)).…”

Section: Microscopic Origin O F Polar Configuration In Ktao3 : LImentioning

confidence: 99%

Orientational glasses

Höchli

Knorr

Loidl

1990

Advances in Physics

733

369

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This review summarizes experimental evidence for the freezing of reorienting moments in solids. The moments may be of dipolar or quadrupolar nature, or both; they belong to one of the constituents of a mixed-crystal solid. Extensive results are reported for the following systems: KC1 doped with hydroxyl, potassium tantalate doped with Li, Na and Nb, alkali halide cyanides and alkali-alkali cyanides, rubidium ammonium dihydrogen phosphate, solid ortho-para hydrogen and argon-nitrogen mixtures. These have clearly glass-like properties. In other systems, results are limited to one or two methods hinting at glass formation; some of those are also reported. Clustering phenomena and the slow-down of reorientations at the freezing temperature are observed in susceptibility measurements and by local probing on nuclear spins. The modulation of the structure by cluster formation is revealed by diffraction experiments. These phenomena are confronted with model predictions and numerical simulations. l , 2. IntroductionWe apply the term 'orientational glass' to a solid consisting of a regular lattice some of whose sites are occupied by constituents containing a dipole or quadrupole moment. These moments have orientational degrees o f freedom; they interact with one another and, below some freezing temperature Tf, their motion slows and they freeze into a configuration devoid of long-range order. A typical example is KC1 doped with OH molecules that replace C1 at random sites. At ! 0 K the dipoles associated with the OH molecules reorient rapidly, whereas at 0-1 K their orientations are static on experimental time scales, yet there is no macroscopic (spontaneous) polarization. Early investigations of this orientational-glass prototype (of the subspecies 'dipole glass') were performed by Kfinzig et al. (1964). Brout (1965)considered its short-range order and pointed out the analogy with what was to become the spin-glass prototype, Cu doped with Mn, where Mn has a spin of ~ and therefore contains magnetic degrees of freedom.The use of the word 'glass' suggests a similarity with what we call ~canonical glasses' (the prototype of which is fused silica, SiO2), in order to distinguish them from orientational and spin glasses. There are indeed orientational degrees of freedom in SiO2, in addition to rapid freezing of the moments and a low-temperature configuration devoid of order. Owing to the lack of an underlying lattice, however, it is impossible to associate moments at site i with interactions between moments at sites i and j, which is a pre-requisite for modelling a glass in terms of a Hamiltonian.Spin-glass models are based almost entirely on the existence of a Hamiltonian containing interactions between spins and their coupling to a magnetic field. The interactions chosen to model spin glasses are, in general, totally unspecific for spins. They are usually probabilistic distributions o f interaction strengths with a variance Var~j much larger than their average ~j and with both quantities independent of i j. The picture of spi...

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Section: Microscopic Origin O F Polar Configuration In Ktao3 : LImentioning

confidence: 99%

Orientational glasses

Höchli

Knorr

Loidl

1990

Advances in Physics

733

369

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“…As a result, the QPE do not undergo a phase transition, and the paraelectric state persists down to the lowest temperatures, T → 0 [1]. Nevertheless, the ferroelectric phase transition can be induced by the introduction of even small concentrations of impurities (of dipole [2,3] or quadrupole [4] type) or application of uniaxial stress [5]. Usually, it is suggested that the ferroelectric phase transition in the QPE can be induced by local symmetry-breaking (SB) defects [2,3], or the soft non-symmetry-breaking (NSB) defects that lead to an increase of the local ferroelectric transition temperature [6].…”

Section: Introductionmentioning

confidence: 99%

“…However, the studies of the three-dimensional lattice ϕ 4 -model with NSB defects [9][10][11] have shown that NSB defects (and hard NSB defects also) and/or anharmonicity of the pure lattice can give rise to a dynamic transition from an ergodic to a non-ergodic state. The non-ergodic state is characterized by the formation of a long-time correlation (LTC) of the fluctuations of the lattice distortions for T d > T c , which correspond to the appearance of quasi-static displacements (precursor order clusters).…”

Section: Introductionmentioning

confidence: 99%

The long-time correlations induced by defects in the quantum paraelectrics and

Smolyaninov

1998

J. Phys.: Condens. Matter

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The long-time correlations of fluctuations of lattice displacements in the quantum paraelectrics and are studied within the framework of the mode-coupling theory of the dynamic transition from an ergodic to a non-ergodic state caused by defects. It is shown that the very hard local non-symmetry-breaking defects formed by the oxygen vacancies can induce the dynamic transition at . The low-temperature non-ergodic state is characterized by long-time correlations of local fluctuations of the polar displacements, which continuously arise for . Simultaneously, the local non-symmetry-breaking defects lead to the appearance of long-time correlations of long-wavelength fluctuations of acoustic displacements via the local random piezoelectric coupling for . The random local piezoelectric coupling is caused by the electrostrictive interaction, which is modified by the random electric fields of the frozen symmetry-breaking defects. The conditions that must be met for the dynamic transition to be induced by the oxygen vacancies are analysed. It is also shown that the unavoidable oxygen vacancies in the nominally pure and are quite sufficient in number to cause the non-ergodic state. The role of the dynamic transition in the formation of the glass state for lightly doped and is discussed.

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Ceramic-matrix composites

Trefilov

1995

Ceramic- And Carbon-Matrix Composites

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Structural phase transition induced by elastic fields of impurities

Abstract: Results of a theoretical and experimental study of cooperative behaviour in soft lattices with off-center ions characterized by elastic dipole moments are presented. The influence of random elastic fields on the impurity-induced ferroelectric phase transition is investigated.

Cited by 7 publications

References 14 publications

Orientational glasses

Orientational glasses

The long-time correlations induced by defects in the quantum paraelectrics and

Ceramic-matrix composites

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