Electron thermal conductivity of superconducting films of indium--gadolinium and lead--gadolinium alloys

We have measured the thermal conductivity of quench-condensed superconducting lead and indium films containing small amounts of gadolinium. The data are in good agreement with the theory of Ambegaokar and Griffin and of Bennemann (modified for strong-coupling effects), except at the lowest temperatures, where problems in the interpretation of the data cause deviations. We have found that strong-coupling effects do not entirely account for the discrepancy between weak-coupling theory and the data of Bjerkaas et al. for the thermal conductivity of quench-condensed films of indium containing small amounts of manganese. Thus, our results support evidence from tunneling and high-frequency electromagnetic experiments that the properties of superconductors with rare-earth impurities are understood, but those with transition-element impurities are not.