Specific Heat of Dysprosium Metal between 0.4 and 4°K

Abstract

The heat capacity of dysprosium has been measured between 0.4 and 4\ifmmode^\circ\else\textdegree\fi{}K in a ${\mathrm{He}}^{3}$ cryostat. In this temperature range the specific heat of the metal can be written ${C}_{p}=A{T}^{3}+BT+C{T}^{\frac{3}{2}}+D{T}^{\ensuremath{-}2}\ensuremath{-}E{T}^{\ensuremath{-}3}\ensuremath{-}F{T}^{\ensuremath{-}4}$. The first term is the lattice specific heat, the second the electronic specific heat, the third the magnetic specific heat caused by exchange interaction between the electronic spins, and the remaining terms are the nuclear specific heat due to splitting of the nuclear energy levels by the strong magnetic field of the $4f$ electrons and by quadrupole coupling. An anomalous contribution to the heat capacity, probably due to the 0.08% oxygen impurity in the sample, was observed between 1.2 and 3.5\ifmmode^\circ\else\textdegree\fi{}K. By excluding the measurements in this temperature region the following values were obtained for the constants in the above equation (for specific heat in millijoules/mole \ifmmode^\circ\else\textdegree\fi{}K): $B=9.5\ifmmode\pm\else\textpm\fi{}10%$, $C=9.7\ifmmode\pm\else\textpm\fi{}10%$, $D=26.4\ifmmode\pm\else\textpm\fi{}2%$. The result $A=0.22$ by Dreyfus et al. was adopted and constants $E=1.32$ and $F=0.12$ were calculated from the available electron-paramagnetic resonance data.Considerable disagreement exists in the temperature range from 2 to 4\ifmmode^\circ\else\textdegree\fi{}K between measurements of the specific heat of dysprosium by different investigators. It is shown, however, that the discrepancies appear to be in the magnetic specific heat only, $C$ varying between 0 and 24. The various values of $B$ are all in good agreement. Our result for $D$ is in excellent accord with the value 26.6 obtained from electron paramagnetic resonance experiments on dilute salts. The magnetic field at the dysprosium nucleus as calculated from the value of $D$ after the effect of quadrupole coupling had been subtracted is 7.1\ifmmode\times\else\texttimes\fi{}${10}^{6}$ gauss, in good agreement with ${H}_{\mathrm{eff}}=7.3\ifmmode\times\else\texttimes\fi{}{10}^{6}$ gauss determined for ${\mathrm{Dy}}^{161}$ by M\ossbauer techniques.