Components of the low-temperature heat capacity of rare-earth hexaborides

Abstract

The temperature dependence of heat capacity Cp(T) was studied for nine rare-earth hexaborides MB6(M=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) at temperatures of 5–300 K. Using the correspondence principle for lattice heat capacities of isostructural compounds, the lattice contribution C1(T) and the excess contribution ΔC(T) to the heat capacity of the hexaborides were determined. The lattice heat capacity C1(T) is represented as the sum of the Debye contributions of the metal and boron sublattices: C1(T)=C M (T)+6CB(T). The Debye temperatures πM and πB of the metal and boron sublattices were determined. The anomalies in the excess heat capacity ΔC(T)=C p (T)−C1(T) are related to the magnetic ordering effects, the Schottky contribution, and the Jahn-Teller effect.