Heat capacity and thermodynamic functions of the RFe 2 compounds ( R =Gd, Tb, Dy, Ho, Er, Tm, Lu) over the temperature region 8 to 300 K

Abstract

Experimental heat capacity data for the Laves phase RFe 2 intermetallic compounds ( R =Gd, Tb, Dy, Ho, Er, Tm, and Lu) have been determined over the temperature range 8 to 300 K. The error in these data is thought to be less than 1%. Smoothed heat capacity values and the thermodynamic functions, ( H° T − H° 0) and S° T, are reported throughout the temperature range for the RFe 2 series. In addition, ( G° 298 − H° 0) at 298 K is reported for all the RFe 2 compounds. These data were analyzed and it was shown that the maxima in the thermodynamic functions near HoFe 2 are due to the magnetic contribution of the lanthanide element. The lattice contribution to the entropy at 300 K was estimated, and from this quantity the Debye temperature was calculated to be about 300 K, which is in good agreement with the low-temperature heat capacity. Furthermore, this analysis indicates that the apparent electronic specific heat constants, γ′, for TbFe 2, DyFe 2, and HoFe 2, reported earlier, are in error.