RESISTIVITY ANISOTROPY AND JOSEPHSON COUPLING IN LEAD-SUBSTITUTED BISMUTH CUPRATES

We report experimental results showing that the increase of the lead-substitution in Bi-2:2:1:2 single crystals can offer the possibility to reduce the anisotropy. The strengthening of the binding forces between adjacent Bi-O planes, induced by lead-substitution, is confirmed by new results about iodine intercalation. In the normal phase, the lead-substitution has the effect to decrease the resistivity along the c-direction by a factor as high as 60. In the superconducting phase, it increases the Josephson coupling between the layers, resulting in high densities of critical current along the c-axis, up to 5 000 A/cm2 and two-state hysteretic I-V characteristics without intermediate branches.