TRANSPORT AND MAGNETIZATION CURRENTS IN BSCCO/Ag TAPES

A (Bi,Pb)SrCaCuO-2223/Ag tape has been produced by thermomechanical processing. Transport J(c)'s have been measured between H = 0 and 7 T and T = 7 to 75 K. Magnetization currents, J(H,T), have been determined for similar temperatures and fields (0 to 5 T) oriented parallel and orthogonal to the thickness of the tape. Dimensional scaling arguments show that flux penetrates most quickly along the tape thickness direction (for fields parallel to the tape plane and therefore the ab planes of the textured BSCCO grains). This implies that the anisotropy ratio of J(c) and J(ab) is reduced in tapes as compared with single crystals consistent with predictions of the brick wall model. Also measured were the H dependence of magnetization currents, and J(H perpendicular to c)ab and J(H perpendicular to c) ab, effective pinning potentials, U-eff(J), for similar field orientations. Fast magnetic relaxation causes an exponential field dependence, J/J(c) alpha exp (-H/H-0) of transport and magnetization currents consistent with a divergent U-eff(J) as J double right arrow 0. Temperature dependences for H-0 for transport and magnetization measurements are interpreted in terms of different time scales (or voltage criteria); for H-0 in two field orientations are explained by a directionally dependent U-eff(J(ab))