Specific Heat of Rhenium between 0.15 and 4.0 K

The specific heat of rhenium has been measured in the normal state between 0.15 and 4.0 K and in the superconducting state between 0.3 and 1.7 K. The specific heat in the normal state between 0.15 and 4.0 K was found to be $C_n=\gamma T+\alpha T^3+\frac{A}{T^2}$, where $\gamma =2290\mathrm{}\pm 20$ μJ/mole ${\mathrm{deg}}^2$, $\alpha =27\mathrm{}\pm 2$ μJ/mole ${\mathrm{deg}}^4$, and $A=49\mathrm{}\pm 2$ μJ deg/mole. Below $T_0=1.700\mathrm{}$ K, the electronic contribution to the specific heat in the superconducting state was found to be $C_s=\gamma T_{0}a{e}^{-\frac{b{T}_0}{T}}$, where $a=8.14\mathrm{}$ and $b=1.413\mathrm{}$. The above parameters were consistent with the vanishing of the entropy difference $S_n-S_s$ at $T_0$. The value of the Debye temperature at absolute zero, ${\Theta }_0=416\mathrm{}$ K, agrees with the value derived from measurement of elastic constants. The density of states at the Fermi level, $N\left(\zeta \right)$, derived from the measured value of $\gamma$, is 0.484 states of one spin per eV atom. The value for the superconducting energy gap derived from the value of $b$ deduced in this work is $3.43k{T}_0$, compared to a value of $3.30k{T}_0$ deduced from thermal-conductivity measurements. The critical-field parameter $H_0$ was found to be 211 Oe, and the deviation of the critical-field curve from parabolic dependence was less than 3.7%. The resonant frequencies corresponding to the interaction between the nuclear quadrupole moment and the crystalline field are estimated to be 41 and 82 MHz.