Upper Critical Field and Critical Current Density in Ceramic Samples of Pb2Sr2Y0.5Ca0.5Cu3O8+δ

Abstract
The electrical resistance of ceramic samples Pb2Sr2Y0.5Ca0.5Cu3O8+δ with zero resistance at 75 K has been measured in magnetic fields up to 21 T. The superconducting transition curve becomes as broad in the field longitudinal to the current direction as in the transverse field. The value of -dH c2/dT is estimated as 1.7–1.8 T/K. The resistive tail in the lower portion of the transition curve is well expressed as ρ=ρ0 exp (-U 0/k B T). The critical current density J c shows hysteresis with respect to the magnetic field sweep, and is as low as 0.1 A ·cm-2 at 4.2 K in magnetic fields between 1 T and 13 T.