SUPERCONDUCTIVITY AND MAGNETISM IN NIOBIUM DOPED YBA2CU3O7 RELATED HIGH T(C) CERAMICS

Magnetic characterization has been performed on the members of the cup rate-niobate RBa2Cu2NbO8 (R = Pr, Nd, and La) series and R1.5Ce0.5Sr2C u2 NbO10 (R = Pr, Eu, Nd, and Sm) series. The PrBCNO samples show a si gnature in the magnetization of a magnetic ordering at 12K. The PrCSCN O sample is nonsuperconducting and shows two distinct orderings at 17K and 53K. No such magnetic phase transition is observed down to 2K in the Nd and La based RBCNO materials or the Nd, Sm, and Eu based RCSCNO materials. Measurements of the lower critical field curve, dc irrever sibility line, and critical current densities are reported for each of the superconducting NdCSCNO, SmCSCNO, and EuCSCNO compounds.