Measurement of the Nuclear and Electronic Contributions to the Specific Heat of Neodymium Ethyl Sulfate near 1 °K

The molar specific heat $C_{\mathrm{I}}$ of neodymium ethyl sulfate has been measured on three samples of separated neodymium isotopes in the temperature range 0.95°K-2.15°K by the magnetic method of Benzie and Cooke at frequencies from 300 to 1200 cps. The measured $C_{\mathrm{I}}$ may be described within 1 percent by $C_{\mathrm{I}}=\frac{b}{T^2}$, where $T$ is the temperature and $b$ is the constant. All three samples were shown by x-ray diffraction measurements to have the same structure as that given for neodymium ethyl sulfate by Ketelaar. For the electron contribution to the specific heat we obtained $b_e=0.146\mathrm{}\pm 0.004\times {10}^5$, and for the hyperfine splitting contributions we obtained $b_{143}=5.08\mathrm{}\pm 0.05\times {10}^5$ and $b_{145}=1.7\mathrm{}\pm 0.2\times {10}^5$ erg degree. These values of $b_{143}$ and $b_{145}$ agree within experimental error with the corresponding values computed from the microwave measurements of Scovil. Thus, the hyperfine splitting contribution to the specific heat for ${\mathrm{Nd}}^{143}$ ${\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{S}{\mathrm{O}}_4\right)}_3$·9${\mathrm{H}}_2$O is some 35 times larger than the electron contribution which makes this material of interest for the study of nuclear effects below 1°K.