Thermophysical Properties of CeB 6 and PrB 6 at Subambient Temperatures

Abstract

Equilibrium adiabatic heat-capacity measurements have been made on zone refined samples of CeB 6 and PrB 6 . Companion measurements made on LaB 6 , NdB 6 , and GdB 6 have been reported elsewhere. These show cooperative lambda-type anomalies associated with antiferro-magnetic ordering. Except for lanthanum hexaboride, Schottky internal crystal field levels result in significant contributions to the thermodynamic functions. The gross thermodynamic properties at 298.15 K heat capacity ( C p / R ), entropy increment (Δ 0,m T S 0 / R ), and Gibbs energy function are correlated with the nature of the lanthanide. For LaB 6 , CeB 6 , PrB 6 , NdB 6 , and GdB 6 the three properties are, respectively: {11.654, 12.014, 11.997, 11.916, 11.695} C p / R ; {10.001, 11.803, 12.430, 12.558, 13.982} S 0 /R, and finally {4.379, 5.912, 6.232, 6.451, 7.905} Φ m 0 / R .