Phase diagram of ferroelectrics with tricritical and Lifshitz points at coupling between polar and antipolar fluctuations

Abstract

Static and dynamic critical behavior of Sn${}_2$P${}_2$S${}_6$ type ferroelectrics and (Pb${}_y$Sn${}_{1-y}$)${}_2$P${}_2$(Se${}_x$S${}_{1-x}$)${}_6$ mixed crystals with line of tricritical points and line of Lifshitz points on the $T-x-y$ phase diagram, which meet at the tricritical Lifshitz point, can be described in a combined BEG-ANNNI model. Such the model considers first and second neighbor interactions for pseudospins in a local three-well potential. Below the temperature of tricritical Lifshitz point, the "chaotic" state accompanied by the coexistence of ferroelectric, metastable paraelectric and modulated phases is expected. In addition to the frustration of polar fluctuations near the Brillouin zone center, in Sn${}_2$P${}_2$S${}_6$ crystal the antipolar fluctuations also strongly develop in the paraelectric phase at cooling to continuous phase transition temperature $T_0$. Here, critical behavior can be described as a crossover between Ising and XY universality classes, what is expected near bicritical points with coupled polar and antipolar order parameters and competing instabilities in $q$-space.

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Cited by in corpus (4)

• Influence of pressure on the kinetics of ferroelectric phase transition in BaTiO3
• Quantum paraelectric state and critical behavior in Sn(Pb)${}_2$P${}_2$S(Se)${}_6$ ferroelectrics
• Slow and fast relaxation times of quantum lattice model with local multi-well potentials: phenomenological dynamics for Sn${}_2$P${}_2$S${}_6$ ferroelectric crystals
• Microscopic flexoelectricity in the canonical PMN relaxor