Phenomenological approaches on the Nd³⁺ doped ferroelectric LaBGeO₅

Abstract

Two phenomenological models, namely the compressible Ising model and Landau model, have been used to analyze the specific heat and the dielectric constant data, respectively for the pure and Nd³⁺ doped LaBGeO₅ (LBG) crystals. The critical exponent of the specific heat was extracted in both ferroelectric and paraelectric phases of the crystals studied here within the temperature intervals of $\left|T-T_C\right|<4\mathrm{ }K.$ The extracted values of the critical exponent were then used to predict some thermodynamic quantities such as the enthalpy, entropy, and the Gibbs free energy. Regarding the analysis of dielectric constant data within the framework of the Landau theory, the observed values of the birefringence were associated with the order parameter below the transition temperature Tc. The Landau coefficients $a_0\mathrm{ }$ and $a_4$ were determined. Our results indicate a second-order phase transition mechanism.

Keywords:

• Specific heat
• critical exponent
• Ising model
• Landau model
• LaBGeO₅