Heat capacity studies on RAuAl compounds (R  La, Ce and Nd)

Abstract

In the RAuAl series, the compound CeAuAl shows Kondo lattice behaviour and orders antiferromagnetically with a Néel temperature of ∼ 3.8 K. The non-magnetic member, LaAuAl, is metallic and non-superconducting down to 2 K, while NdAuAl, has a ferromagnetic ground state with a Curie temperature of ∼ 10 K. Heat capacity measurements have been carried out on these compounds in the temperature range 2–20 K. The electronic specific heat coefficient, γ, of LaAuAl is ∼ 1 mJ/mol K 2, typical of normal metallic systems. The heat capacity of CeAuAl shows a rise at about 4 K due to the magnetic ordering. The γ value for CeAuAl, in the temperature range 8–15 K, is ∼ 100 mJ/mol K 2, and the entropy change due to magnetic transition is about 4 J/mol K which is appreciably reduced compared to the value Rln(2) expected for a crystal-field-split doublet ground state. In the case of NdAuAl, a rise in the heat capacity is observed at about 10 K due to the ferromagnetic ordering while the entropy change due to the transition is about 5.3 J/mol K—close to the value of Rln(2).