Heat capacity studies in RPd₂Al₃ (R = Ce, Pr, Nd and Sm) systems

Abstract

In this paper we report the results of low-temperature (from 1.7 to 40 K) heat-capacity studies in RPd₂Al₃ (R = Ce, Pr, Nd and Sm). Our heat-capacity data on CePd₂Al₃ and SmPd₂Al₃ agree with those of the previous studies. A λ-type anomaly is observed at 6.0 K for NdPd₂Al₃. A large jump (11 J/mol K) in heat-capacity data near the magnetic transition temperature confirms the bulk magnetic ordering in NdPd₂Al₃. The data for PrPd₂Al₃ do not show any magnetic ordering down to 1.7 K. We have calculated the magnetic contribution of entropy due to 4f electrons of all the samples. The temperature dependence of entropy in PrPd₂Al₃ indicates a nonmagnetic singlet ground state. The magnetic contribution to the entropy for all samples at 40 K is less than the corresponding free ion entropy values (R ln(2J + 1)). This suggests that there is a large crystal-field contribution to the heat-capacity in this series.