Critical currents of Bi:2212 doped by Fe and Ni

Measurements of the irreversible magnetization, ac susceptibility and electrical resistivity of Bi2Sr2Ca1−xErx(Cu1−yMy)2O8+d bulk are reported. Low concentrations of the doping elements increase the pinning force density and shift the magnetic irreversibility line towards higher fields. The intergranular critical current density was determined from ac susceptibility data by varying the field amplitude Hac in the range from 0.4 to 1000 A/m and from the irreversible part of magnetization using Bean’s model. The results were discussed in terms of SIS- and SNS-type models for granular superconductors.