Specific Heat Capacity of Pb_1−xGe_xTe at Their Structural Phase Transitions

Abstract

The specific heat capacity of Pb_1−xGe_xTe has been measured by means of a.c. calorimetry method in x ranging from 0.05 to 0.3. We found that the specific heat capacity exhibits a steplike behavior at T_c up to x=0.07 and additionally critical behavior becomes appreciable at x=0.3. These trends are very similar to those in Sn_1−yGe_yTe. The anomalous specific heat above T_c was found to fit well to logarithmic law. The jump ΔC_p is 0.92 J mol⁻¹K⁻¹ in the crystal with x=0.05, which is comparable with the value 0.87 J mol⁻¹K⁻¹ estimated by using the Landau-type free energy expansion coefficients by Sugai et al. The increase of ΔC_p with T_c is well explained by assuming that T_c is close to tricritical point.