ANALYSIS OF THE EXCESS RESISTIVITY INDUCED BY A LOW MAGNETIC-FIELD INYBCO AND BSCCO COMPOUNDS

The results of a (weal;) DC magnetic field induced excess resistivity in granular high-temperature superconductors are analyzed. Assuming a random mixture of superconducting and normal regions, the two characte ristic excess resistivity peaks are interpreted as originating from tw o different mechanisms: the higher temperature peak in excess resistiv ity is attributed to a distribution of the critical temperature in ind ividual grains affected by the applied magnetic field, this results in a quasi-percolative normal current energy dissipation. The lower temp erature wide peak is attributed to an interplay between strong pinning due to the spatial inhomogeneity of the condensation energy on one ha nd and to the onset of proximity effect with decreasing temperature, o n the other. The results obtained with various concentrations of Ag ad mixture and under varying magnetic field are consistent with the predi ctions of this model. (C) 1998 Published by Elsevier Science B.V. All rights reserved.