Pressure behaviour of the birefringence in Sn2P2(S1-xSex)6 crystals in the vicinity of the Lipshitz point

Abstract

The temperature dependences of the birefringence of Sn2P2(S1-xSex)6 ferroelectric crystals with x=0; 0.1 and 0.2 at high hydrostatic pressures (to 0.4 GPa) have been investigated. On the base of the analysis of the birefringence behaviour in the region of the phase transition the b critical exponent of the order parameter and the a thermal capacity have been determined. The pressure dependences for investigation of crystals in the vicinity of the Lifshitz point have been built.