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Irreversible magnetization and critical currents in silver-sheathed (Bi, Pb)_2Sr_2Ca_2Cu_3O_10+y tape

Irreversible magnetization of an Ag-clad Bi(Pb)-Sr-Ca-Cu-O tape has been measured in the temperature range 7 to 90 K in magnetic field B less than or equal to 5 T applied perpendicular to the tape plane. Intergranular (bulk) critical current density J(c)(B), deduced from the low Geld virigin moment m(v), extrapolates well to the transport critical current density J(c) of the same tape measured for T > 77 K. Both J(c)(B) and J(c) follow the same (1 - T/T-c)(n) variation with n approximate to 1.5. The intragranular critical current density J(c)(G), deduced from the variation of remanent moment m(R) with maximum field H-m, decreases faster with temperature similar to exp(-T/T-0) with T-0 congruent to 20 K for T less than or equal to 55 K) than J(c)(B) which results in a J(c)(G)/J(c)(B) ratio that decreases with increasing temperature. Since J(c)(G)/J(c)(B) approximate to 16 at 77 K this leaves an ample space for the enhancement of J(c)(B) (approximate to J(c)) in tapes. The temperature dependence of the irreversibility field B-irr is similar to that of J(c)(G).

high T_c superconductivity ; critical currents ; magnetization

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