Heat Capacity of Europium from 5°—300°K

The heat capacities of two samples of Eu have been measured, one in the range 12°—300°K and another in the range 5–300°K. A sharp transition was found in the neighborhood of 88°K, the temperature of the peaks differing by 0.3°K in the two samples, and the height of the peaks differing by roughly a factor of 2. Reasonable values of lattice and electronic contributions yield a magnetic entropy of R ln8 at room temperature in accordance with the ion core being divalent over the entire temperature range measured. This value for the magnetic entropy is not unambiguously determined by our analysis, however. The thermodynamic functions for the two samples agree at room temperature to within 0.2% and are found to be as follows: $${\mathrm{(H}}_{\text{298.15}}^{\circ }{\mathrm{-H}}_0^{\circ }\text{)/T=26.86\hspace{0.17em}}\mathrm{J}\mathrm{\hspace{0.17em}(g·}\mathrm{at}\mathrm{.\hspace{0.17em}}\mathrm{wt}·\mathrm{deg}{)}^{\text{−1}}{\mathrm{,\hspace{0.17em}\hspace{0.17em}S}}_{\text{298.15}}^{\circ }\text{=77.81\hspace{0.17em}}\mathrm{J}\mathrm{\hspace{0.17em}(g·}\mathrm{at}\mathrm{.\hspace{0.17em}}\mathrm{wt}·\mathrm{deg}{)}^{\text{−1}}.$$