Temperature dependences of nonlinear dielectric susceptibilities of triglycine sulphate near ferroelectric phase transition

Abstract

The linear, second-order, and third-order, dielectric susceptibilities χ₁, χ₂, χ₃, of triglycine sulphate (TGS) single crystal have been measured using dynamic method. The second-order dielectric susceptibility has non-zero value in ferroelectric phase and vanishes near the temperature of ferroelectric phase transition. The change in the sign of the third-order dielectric susceptibility, χ₃, as predicted by the thermodynamic theory of the continuous phase transitions is confirmed experimentally. The nonlinearity coefficient, B, has been evaluated with the use of the measured values of the linear and the third-order dielectric susceptibilities. Both, the change in the sign of χ₃ and the temperature independence of the nonlinearity coefficient, B, within the temperature range of T≤T_C +2 K above the phase transition temperature point, confirm that the TGS belongs to the Landau universality class.

Keywords:

• TGS
• Phase transition
• Nonlinear dielectric susceptibilities

Acknowledgments

This work was partially supported by Polish Committee for Scientific Research under the grant 4 T08A 007 25.