Initial magnetization curve M(H) and magnetic relaxation M(t) were studied on the Ag-sheathed and highly c-axis oriented tape of Bi-Pb-Sr-Ca-Cu-O with transport Jct=5400 and 2400 A/cm2 (77 K, H=0). The Jc value, derived from M(H) curve based on Bean’s critical-state model, agrees fairly well with the Jct. The lower critical field Hc1 for H⊥c axis from M(H) curve increases with a slope of −0.2 Oe/K as temperature decreases from Tc, and it approaches the saturated value of 15 Oe at T∼0 K. The magnitude is much lower than that for the high-Tc superconductors La-Sr-Cu-O and Y-Ba-Cu-O. The creep rate and activation energy U0 are evaluated from M(t) based on the flux creep model. The results show a significant dependence on the measuring process and magnetic field H. The U0 at 5 K for H=500 Oe (H⊥c) is 0.4 eV for the in-field magnetization (IN) and 0.1 eV for the remanent magnetization (REM), which are larger than those for Bi-based high-Tc superconductors reported previously. The U0 for the IN shows a peak of 0.8 eV around 30 K and then decreases as temperature increases, while a peak in it is weakened for the REM. The U0 at H=30 Oe (H⊥c) for the IN is one order larger than that for 500 Oe and the peak temperature is shifted to the lower temperature (∼10 K).

Magnetic relaxation M(t) for remanent magnetization is studied on the Agsheathed tape of Bi-Pb-Sr-Ca-Cu-0 with transport J,t=13000 A/cm2 (77K. H=O Oe). a nearly-pure high-", phase and highly-oriented microstructure. A correlation between the starting magnetization Mi=M(ti). and the creep rate R=d(rlnM)/dlnt appears in the result for Hlc, and the empirical relation IRI = Mi stands for the full critical-state with a full flux-entry. The field-independent activation energy U,t in the full critical-state increases linearly with temperature, which is consistent with the relation IRI = Mi. No difference appears in the temperature dependenmof Ust between KLc and H II c.

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The repet ition process of cold-workyg and sintering yields a maximum transport Jc of 8500A/cm (77K, H=O) in Ag-sheathed tapes .of Bi (Pb)-Sr-ta-Cu-0. The tapes contain the pure high-Tc phase and c-axis oriented microstructures. The initial magnetization M(H) and magnetic relaxation M(t) are studied on high-J-tapes. The J_ and H-, are evaluated from M(H) using Bean's" critical-state" model the results are discussed. The creep rate and activation energy are derived from M(t) using the flux creep model and the pinning nature is discussed.