Specific heat of superconducting films of indium and of indium alloyed with magnetic impurities

Measurements were made of the discontinuity Δc in the specific heat at the superconducting transition for quench-condensed films of indium, indium-manganese, and indium-chromium. This is the first investigation of this sort where 3-d magnetic impurities have been studied in a simple metal superconductor. Magnetic impurities is also depress the superconducting transition temperature T/sub c/, and predictions based on the Shiba theory for classical spins in superconductors indicate that Δc depressed by the presence of magnetic impurities. It is useful to express the result more rapidly than T/sub c/Tc0 as magnetic impurities are introduced into a superconductor. The result of the present work confirm this prediction, but show an even greater depression of Δc/Δc0 relative to Tc/T/sub c/0 than the Shiba theory predicts. Similar results have been obtained by previous workers who dissolved 3-d magnetic impurities in transition metal superconductors. The present work also shows that Δc for pure indium increases with increasing disorder, where the degree of disorder is indicated by the residual resistivity of the sample. This result is to be expected qualitatively from Bergmann's studies of the transition temperature and energy gap width for disordered samples of indium. The present results, however, indicate that Δc increases roughly ten times more rapidly with the degree of disorder than would be estimated from the results of Bergmann