Surface Superconductivity in Type I and Type II Superconductors

The real and imaginary parts of types I- and II-superconductor a-c susceptibility were measured in both parallel and perpendicular d-c magnetic fields. A surface superconducting layer with critical field H/sub c3/ was found to exist for parallel external field if H/sub c3/ was only barely above the bulk critical field. Preliminary measurements demonstrating that H/sub c3/ can exist in a pure material as well as an alloy were made. (M.J.T.) 21l02 The finding of superconducting transitions in samples of reduced strontium titanate is reported. The transitions occurred at approximates 0.25 and 0.28 deg K. lt was ascertained that the superconductivity was a bulk effect. (C.E.S.)