Frequency shifts of the disorder-induced modes close to the tricritical phase transition in NH4Cl

Yurtseven H., Kayisoglu D.

HIGH TEMPERATURES-HIGH PRESSURES, no.4, pp.471-476, 2003 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Publication Date: 2003
  • Doi Number: 10.1068/htjr068
  • Journal Name: HIGH TEMPERATURES-HIGH PRESSURES
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.471-476
  • Middle East Technical University Affiliated: Yes

Abstract

We have studied the Raman frequencies of the disorder-induced modes of v, (93 cm(-1)) and v(5) (144 cm(-1)) close to the tricritical phase transition in NH4Cl (P 1.6 kbar, T. 257 K). Using our observed Raman data for these phonon modes, we have obtained the value of the exponent a approximate to 0.3 for the frequency shifts, which can describe the critical behaviour of the thermal expansivity a, and also of the specific heat Cp. Our exponent value can be compared with the value of 0.1 predicted by the 3d Ising model.