Transport and magnetization current in a thin layer of Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2.0}Ca{sub 2.2}Cu{sub 3.0}O{sub y} adjacent to silver sheathing in BSCCO-2223 tapes

Abstract

The thin superconducting region next to the silver sheath appears to be the region of high critical current density in BSCCO-2223 tapes. Transport current measurements on Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2.0}Ca{sub 2.2}Cu{sub 3.0}O{sub y} tape at 77 K in a low magnetic field applied parallel to the tape thickness indicate an exponential field dependence [J / J{sub c} {proportional_to} exp (- B / B{sub 0})] for transport currents. Magnetic hysteresis was measured in a 10-{mu}m-thick layer of superconductor near the silver sheath as a function of temperature, intensity, and orientation of applied field with respect to the tape. The characteristic field for full penetration depth, B*, for a superconducting slab was found to have a power law dependence on temperature. Magnetization currents as a function of temperature and applied field oriented parallel to the tape thickness, J{sub c,m}(B,T), were determined from the magnetization loop width with a Bean- model expression adapted for an orthorhombic sample. The critical-state model, adjusted for scaling and magnetic relaxation, correlates well with the magnetization current of the thin layer at 77 K.