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Soft modes in ferroelectric superlattices
Ferroelectrics, 1990Abstract A phenomenological theory of periodic ferroelectric multilayers, consisting of two alternating ferroelectrics with different transition temperatures, is presented. We consider the case of a ferroelectric phase transition of first order. Interface modes are shown to exist, resulting from the special form of the inhomogeneous polarization ...
D. Schwenk, F. Fishman, F. Schwabl
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Phase Transitions and Soft Modes
Physical Review A, 1972The stability of an equilibrium phase is described in thermodynamics in terms of certain convexity properties of the free energy. The phase is said to be unstable with respect to an equilibrium phase transition if the isothermal response of the system to a static external field is infinite. It is also known that associated with several second-order and
T. Schneider, G. Srinivasan, C. P. Enz
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On the infrared activity of soft modes
Physics Letters A, 1974Abstract The relation between the soft-mode infrared activity and proper, improper and non-ferroelectricity is discussed. The soft mode can be infrared active in the distorted phase even at non-ferroelectric transitions. The dielectric anomaly in these cases is also discussed.
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Soft Modes in Molecular Crystals
The Journal of Chemical Physics, 1971The self-consistent phonon approximation is applied to study the temperature dependence of the libron and phonon modes for simple molecular crystals. Several linear chain models are studied to illustrate the soft mode behavior of these excitations near the orientational order—disorder transitions that occur in many molecular crystals.
J. C. Raich, R. D. Etters
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The soft-mode ferroelectric effect
Ferroelectrics, 1988Abstract In this paper a presentation is given of some of the basic physics of the soft-mode ferroelectric effect, along with its experimental background. Further, possible applications in electrooptic devices are elucidated. A fast (sub-microsecond) electrooptic switching can be achieved in the A* phase, and in similar orthogonal smectic phases made ...
G. Andersson +5 more
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Superconductivity and soft modes in CdS
Zeitschrift f�r Physik B Condensed Matter, 1987We show that adequate superparacurrent is induced by a magnetic field in an insulator provided soft modes can be identified at the edge of a zone, and there is strong unsymmetric electron-phonon coupling. It is thought that this analysis is relevant to the situation in CdS, where correlation between the occurrence of soft modes and unusual magnetic ...
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Journal of the Physical Society of Japan, 1973
The spin-wave theory is developed for the study of the acoustic soft-magnon modes in hematite (α-Fe 2 O 3 ). The energies ω 0 of the soft-modes are approximately given as ω 0 ∞| T M - T | 1/2 near the Morin phase transition temperature T M and the results are compared with the AFMR experiments.
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The spin-wave theory is developed for the study of the acoustic soft-magnon modes in hematite (α-Fe 2 O 3 ). The energies ω 0 of the soft-modes are approximately given as ω 0 ∞| T M - T | 1/2 near the Morin phase transition temperature T M and the results are compared with the AFMR experiments.
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On the soft modes in (CH3NH3)2CdCl4
Physica Status Solidi (a), 1977The structural phase transitions in the perovskite-type layer-compound (CH3NH3)2CdCl4 are analyzed in order to justify an order-disorder model which is based on the interaction among the CH3NH3-groups, each of which has four possible equilibrium positions.
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Philosophical Magazine B, 2001
Abstract The concept of atomic soft modes in glass dynamics and general assumptions and some basic results of the soft-mode dynamics theory of glasses are discussed in the light shed by experimental observations. Negative- U centres as actual electronic mobility-gap centres, vast pressure-induced effects in dynamics, quasilinear frequency dependence of
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Abstract The concept of atomic soft modes in glass dynamics and general assumptions and some basic results of the soft-mode dynamics theory of glasses are discussed in the light shed by experimental observations. Negative- U centres as actual electronic mobility-gap centres, vast pressure-induced effects in dynamics, quasilinear frequency dependence of
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Physical Review Letters, 1969
The self-consistent phonon formalism, successful in the description of the quantum crystals ${\mathrm{He}}^{3}$ and ${\mathrm{He}}^{4}$, is here applied to a discussion of the soft $k=0$ TO mode in SnTe. Straightforward considerations allow us to arrive at a simple expression for $\ensuremath{\omega}_{\mathrm{TO}}^{}{}_{}{}^{2}(k=0)$ in the low ...
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The self-consistent phonon formalism, successful in the description of the quantum crystals ${\mathrm{He}}^{3}$ and ${\mathrm{He}}^{4}$, is here applied to a discussion of the soft $k=0$ TO mode in SnTe. Straightforward considerations allow us to arrive at a simple expression for $\ensuremath{\omega}_{\mathrm{TO}}^{}{}_{}{}^{2}(k=0)$ in the low ...
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