LOW-FIELD BEHAVIOR OF CRITICAL-CURRENT IN SM1-X-BA2-CU3+X-O7-DELTA CERAMIC SUPERCONDUCTOR

Abstract

The transport critical current I(c) carried by ceramic Sm1-xBa2-Cu3+x-O7-delta (SBCO) superconducting samples (prepared by the coprecipitation technique using organic carbonate in the presence of stable polymer) in low magnetic fields (0-100 Oe) have been investigated at different temperatures close to the critical transition temperature T(c). A significant reduction of the transport current-carrying capacity has been observed for magnetic fields smaller than the lower critical field H(cl). A semilog plot of the field dependence of the transport critical current density J(ct) reveals a well-defined field value H(c)' characteristic of a crossover between regions dominated by the inter- and intragranular effects. Microwave measurements show evidence of a reduction in the total number of weak links between the network of the superconducting grain structure for Cu-rich-SBCO samples. The enhancement of J(tc) for Cu-rich SBCO samples is due to the increase in hole concentration caused by partial replacement of Sm by Cu which caused physical densification between the network of superconducting grain structure in SBCO.