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On the critical exponent of order parameter in Sn2P2S6 and Sn2P2(Se0.28S0.72)6 crystals
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Vasylkiv Yu., Mys O., Zapeka B. and Vlokh R.

Abstract. We have determined critical exponents of the order parameter in ferroelectric Sn2P2S6 and Sn2P2(Se0.28S0.72)6 crystals at the atmospheric pressure. They are equal to 0.29+/-0.02   for Sn2P2S6 and  0.24+/-0.02  for Sn2P2(Se0.28S0.72)6. These value suggest that, with changing selenium concentration from x = 0 up to x = 0.28, the solid solutions Sn2P2(SexS1–x)6 approach the conditions of tricritical point, which is realised in the vicinity of x = 0.28. The conclusion agrees well with the results of our recent works derived with the other techniques.

Keywords: optical birefringence, ferroelectric phase transition, spontaneous strain, critical exponent 

PACS: 78.20.Fm, 65.40.De, 64.60.Fr, 77.80.–e
UDC: 535.5, 536.411/.416, 537.226.4, 536.42
Ukr. J. Phys. Opt. 13 135-141
doi: 10.3116/16091833/13/3/135/2012
Received: 22.01.2012

Анотація. В даній роботі визначені критичні індекси параметру порядку для сегнетоелектриків Sn2P2S6 і Sn2P2(Se0.28S0.72)6 при атмосферному тиску. Вони дорівнюють 0.29+/-0.02 для Sn2P2S6 та 0.24+/-0.02 для Sn2P2(Se0.28S0.72)6. Дані значення свідчать про те, що при зміні концентрації селену від x = 0 до x = 0.28, тверді розчини Sn2P2(SexS1–x)6 прямують до умов трикритичної точки, яка реалізується в околі x = 0.28. Цей висновок узгоджується з результатами наших попередніх робіт.
REFERENCES
 
  1. Slyvka V Yu and Vysochanskii Yu M, Ferroelectrics of Sn2P2S6 family. Properties around the Lifshitz point, Uzhgorod, Zakarpattya, 1994
  2. Oleaga A, Salazar A, Massot M and Vysochanskii Yu M, 2007. Thermal diffusivity and critical behaviour of uniaxial ferroelectric Sn2P2S6. Thermochimica Acta 459: 73–79. DOI:10.1016/j.tca.2007.04.018
  3. Oleaga A, Salazar A, Kohutych A A and Vysochanskii Yu M, 2011. Critical behavior near the Lifshitz point in Sn2P2(S1–xSex)6 ferroelectric semiconductors from thermal diffusivity measurements J. Phys.: Condens. Matter. 23: 025902. DOI:10.1088/0953-8984/23/2/025902
  4. Martynyuk-Lototska I, Say A, Mys O and Vlokh R, 2011. On the tricritical point on the (p,T)-phase diagram of Sn2P2S6 crystals. Phil. Mag. 91: 4293–4301. DOI:10.1080/14786435.2011.613413
  5. Martynyuk-Lototska I, Mys O, Zapeka B and Vlokh R, 2011. About the existence of a Lifshitz point on the phase diagram of Sn2P2(SexS1–x)6 solid solutions: acoustic and optical studies. Phil. Mag. 91: 3519–3546. DOI:10.1080/14786435.2011.581705
  6. Vysochanskii Y M, Janssen T, Currat R, Folk R, Banys J, Grigas J and Damulionis V, Phase transitions in ferroelectric phosphorous chalcogenide crystals, Vilnius, University Publishing House, 2006. 
  7. Andersson O, Chobal O, Rizak I and Rizak V, 2009. Tricritical Lifshitz point in the temperature–pressure–composition diagram for (PbySn1−y)2P2(SexS1−x)6 ferroelectrics. Phys. Rev. B. 80: 174107. DOI:10.1103/PhysRevB.80.174107
  8. Smolenskiy G A, Physics of ferroelectric phenomena, Leningrad, Nauka, 1985
  9. Patashinskii A Z and Pokrovskii V L, Fluctuation theory of phase transitions, Pergamon Press, 1979. 
  10. Vysochanskii Yu M, Furtsev V G, Khoma M M, Grabar A A, Gurzan M I, Maior M M, Perechinskii S I, Rizak V M and Slivka V Yu, 1986. Critical behavior of Sn2P2(SexS1–x)6 uniaxial ferroelectrics near the Lifshitz point. Zh. Eksp. Teor. Fiz. 91: 1384–1390. 
  11. Vysochanskii Yu M, Mitrovcij V V, Grabar A A, Perechinskii S I, Motrija S F and Kroupa J, 2000. Birefringence investigations of the Sn2P2(SexS1–x)6 uniaxial ferroelectrics behaviour near the Lifshitz point. Ferroelectrics. 237: 193–200. DOI:10.1080/00150190008216249
  12. Samulionis V, Banys J, Vysochanskii Yu and Grabar A A, 1999. The critical behaviour of ultrasonic velocity at a second-order phase transition in Sn2P2S6 single crystals. Phys. Stat. Sol. (b) 215: 1151–1156. DOI:10.1002/(SICI)1521-3951(199910)215:2<1151::AID-PSSB1151>3.0.CO;2-F
  13. Say A, Mys O, Grabar A, Vysochanskii Yu and Vlokh R, 2009. Thermal expansion of Sn2P2S6 crystals. Phase Trans. 82: 531–540. DOI:10.1080/01411590903079003
  14. Say A, Mys O, Adamenko D, Grabar A, Vysochanskii Yu, Kityk A and Vlokh R, 2010. Critical exponents of phase transition in ferroelectric Sn2P2S6: comparison of optical and dilatometric data. Phase Trans. 83: 123–139. DOI:10.1080/01411590903553452
  15. Zapeka B, Mys O and Vlokh R 2011. On the order of phase transition in Sn2P2(Se0.28S0.72)6 solid solutions: optical birefringence studies. Ferroelectrics. 418: 143–149 DOI:10.1080/00150193.2011.578985
  16. Mayor M M, Vysochanskii Yu M, Prits I P, Molnar Sh B, Slivka V Yu, Rogach E D, Savenko F I and Kudinov A P, 1991. Piezoelectric effect in Sn2P2S6 single crystals. Izv. AN SSSR, Ser. Neorg. Mater. 27: 604–606. 
  17. Zapeka B, Vasylkiv Yu, Mys O and Vlokh R, 2011. On the tricritical behaviour of the Sn2P2S6 crystals. Phase Trans. 84: 193–203. DOI:10.1080/01411594.2010.497914
  18. Say A, Mys O and Vlokh R, 2010. Thermal expansion of the Sn2P2(Se0.28S0.72)6 solid solutions. Phil. Mag. 90: 3389–3400. DOI:10.1080/14786435.2010.485937
  19. Adamenko D I, Klymiv I M, Vasylkiv Y and Vlokh R O, 2009. Optical activity and critical exponent of the order parameter in lead germanate crystals. 1. The case of diffused phase transition in Pb5Ge3O11 doped with Cu, Ba and Si ions. Ukr. J. Phys. Opt. 10: 182–193. DOI:10.3116/16091833/10/4/182/2009
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