Pb substitution effects on the critical current density in MgO doped Bi2212 crystals

For heavily Pb substituted Bi2212 crystals with MgO doping, we found not only the critical current density J_c anisotropy decreasing to a half as much as Pb free MgO doped crystals but J_c and irreversibility field B_irr improvement. Apparent pinning potential U₀* derived from flux creep experiments for these crystals also increased. Those results suggest that the effect of MgO doping is more pronounced by decreasing the J_c anisotropy of crystals. Dislocation increase in the Pb substituted Bi2212 crystals due to MgO doping was observed with a transmission electron microscope