Superconducting intermediate state in white tin near H-c: new results by mu SR

A depression of the critical field H-c, predicted for the transition From t he normal (N) to the intermediate (1) state in thin plates of type 1 superc onductors, was spectroscopically confirmed for the first time. In an ultra- high purity single-crystal plate of white tin oriented normal to the applie d field H, the N-I transition occurs at H = H-cI approximate to 0.94H(c). N o hysteresis was seen as the field varied (in steps of 10 G) upwards and do wnwards. The average field B in the N domains is found to be H-eI at the tr ansition, increasing towards H-c with further lowering of H. The huge asymm etrical peak in the damping rate of the precession signal, observed in the range of the initial growth of the S domains, can be a sign of a topologica l transition from a tubular to a laminar structure. (C) 2000 Elsevier Scien ce B.V. All rights reserved.