Two-Step Superconducting Transition of a Bi-Sr-Ca-Cu-O System

Abstract

The ac susceptibility χ=χ'-i χ'' was used for examining the superconducting nature of a two-step transition in a Bi-Sr-Ca-Cu-O specimen. The X-ray diffraction pattern indicates that the crystalline habit of our specimen is tetragonal (a=3.81 Å, c=30.7 Å). Although both bulk and weakly coupled components appeared in the lower-T _c phase of the sintered pellet, the latter phase was fully depressed by pulverization. The pulverization remarkably altered the transition profile of the higher-T _c phase. The implications of these results are discussed.