CURRENT-VOLTAGE CHARACTERISTICS OF HIGH-TEMPERATURE SUPERCONDUCTING CERAMICS WITH THE PEAK EFFECT IN THE MAGNETIC-FIELD DEPENDENCE OF THE TRANSPORT CRITICAL-CURRENT DENSITY

The experimentally determined current-voltage characteristics of high- T-c superconducting ceramics exhibiting the ''peak-effect'' in the mag netic field dependence of the transport critical-current density were described in terms of thermally activated flux creep at grain boundari es; taking into account the collective pinning of intergranular vortic es. The peak effect was explained by considering the increase of the i ntergrain pinning potential at intermediate fields through the interac tion of intergranular (Josephson type) vortices and intragranular (Abr ikosov) vortices. The magnetic field dependences of the effective pinn ing potential and of the collective pinning exponent were experimental ly determined, and the features of the I-V curves were explained throu gh these dependences.