PERCOLATIVE BONDS AND RESISTANCE NOISE IN HIGH-T-C BULK SUPERCONDUCTORS

To explain the behaviour of the resistive noise versus resistance in a bulk polycrystalline YBCO superconductor in a d.c. magnetic field, tw o types of inactivated bonds, in the frame of percolation theory, are suggested. This behaviour is experimentally obtained in bulk polycryst alline YBCO samples when the magnetic field is increased at temperatur es below that corresponding to the superconductor-norma transition in the absence of the magnetic field. By obtaining the same peak with a n umerical simulation based on a modified percolation theory, it was pos sible to verify the validity of the proposed model.