Superconducting Properties of Technetium

Isothermal magnetization measurements are reported for technetium in the superconducting state from 1.5°K to the transition temperature after various stages of heat treatment up to 2000°C. The purer sample studied ($\Gamma =120\mathrm{}$, where $\Gamma$ is the ratio of resistance at 295°K to the resistance at 9°K) was found to have a transition temperature of 7.73±0.02°K, and was destroyed in an early attempt at annealing, while the second sample ($\Gamma =97\mathrm{}$), which had a transition temperature of 7.77±0.02°K, was studied more thoroughly. The magnetic behavior of this material is characteristic of a type-II superconductor, and the experimental temperature dependence of $H_{c2\mathrm{}}$, the upper critical field, is compared with existing theories. Upper limits to the thermodynamic critical field $H_c\mathrm{}\left(t\right)\mathrm{}$, which have been obtained by integrating under the nonreversible magnetization curves observed after the 2000°C heat treatment, lead to an extrapolated value of $H_c\mathrm{}\left(0\right)\mathrm{}$ =1410 Oe, and a Ginzburg-Landau parameter of ${\kappa }_1\mathrm{}\left(1\right)=0.92\mathrm{}$. The data suggest that technetium is a weak-coupling superconductor of the BCS type, and the results are examined for self-consistency.