Specific Heat of Cerium and Europium Metals between 0.4 and 4°K

Abstract

The specific heats of cerium and europium metals have been measured between 0.4 and 4°K in a ${\mathrm{He}}^3$ cryostate. For cerium, two experiments were made with samples consisting of 62 and 39% of the $\alpha$ phase (fcc), the balance being $\beta$ cerium (hex). Due to a pronounced peak at 12.5°K the specific heat is quite large already at 4°K. A previously unknown flat anomaly in $C_p$ was found around 0.8°K. By combining the present measurements with those of Parkinson and Roberts (3% of $\alpha$ cerium) and by assuming $C_L=0.612\mathrm{}{T}^3$ and $C_E=10.5T$ (specific heats always given in mJ/mole°K) for the lattice and electronic specific heats of the trivalent $\beta$ phase an analysis gave $C_p=x(0.50\mathrm{}{T}^3+21T)+(1-x)(0.612\mathrm{}{T}^3+10.5T+C_M)$. Here $x$ is the fraction of $\alpha$ cerium in the sample and $C_M$ is the magnetic specific heat of the $\beta$ phase. $C_E$ is thus about twice as large for the quadrivalent $\alpha$ phase as for $\beta$ cerium. In the former modification $C_M=0\mathrm{}$ because there is no magnetic $4f$ electron. Since all of the stable isotopes of cerium are even-even nuclei the nuclear specific heat $C_N=0\mathrm{}$.