Josephson coupling between superconducting clusters in high-T-c materials

Diamagnetic moment for Bi2Sr2CaCu2O8+delta (Bi:2212) and YBa2Cu3O7-delta (Y :123) crystals were measured at different fields H and temperatures. For th e higher fields two distinct transition temperatures T-g and T-j are identi fied, with T-g > T-j. By increasing H the line T-g(H) shifts very slowly wh ile T-j(H) shifts much faster to lower temperatures. displaying an upward c urvature well described by a theory based on Josephson coupling between sup erconducting clusters. Here, we show data mainly for the Bi:2212 crystals, where sample dependent T-j(H) lines are clearly observed. (C) 2001 Elsevier Science BN. All rights reserved.