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The Critical Behaviour of Ultrasonic Velocity at a Second‐Order Phase Transition in Sn 2 P 2 S 6 Single Crystals
Author(s) -
Samulionis V.,
Banys J.,
Vysochanskii Yu.,
Grabar A. A.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199910)215:2<1151::aid-pssb1151>3.0.co;2-f
Subject(s) - tricritical point , critical exponent , condensed matter physics , ferroelectricity , landau theory , phase transition , phase diagram , critical point (mathematics) , physics , ultrasonic sensor , dielectric , mathematical physics , chemistry , phase (matter) , thermodynamics , quantum mechanics , mathematics , mathematical analysis , acoustics
Precise measurements of the ultrasonic velocity have been performed in Sn 2 P 2 S 6 single crystals in the temperature interval 290 to 420 K. It was shown that in the paraelectric phase above T c ≈ 337 K the anomalous part of the ultrasonic velocity changes with critical exponent α = 0.5 with small multiplicative logarithmic correction, which is in agreement with renormalization group theory calculations of Folk et al. [1] for proper uniaxial ferroelectrics near the tricritical Lifshitz point on the phase diagram. In the ferroelectric phase the Landau‐Khalatnikov theory is a good approximation to describe the critical ultrasonic velocity behaviour in Sn 2 P 2 S 6 .