Complex Susceptibilities of Co-doped YBa₂Cu₃O_7-d Synthesized by the Polymerized Comples Method

Abstract

We studied the ac-magnetic response of Co-doped YBa₂Cu₃O_7-d oxide superconductors, YBa₂Cu_3-xCo_xO_7-d (x=0-0.5), in terms of complex susceptibility χ=χ'-iχ". The samples were synthesized by the polymerized complex method. We found the onset temperature decreased with increasing x, and for x ?? 0.4, no superconducting transition was observed down to 5 K. The transition width ΔT(10-90%) for the sample of x=0.05 is 1.9 K, which is much better than that of the specimens prepared by the ordinary treatment. The transition width was also found to increase as x increases. Details of the experiment are presented together with some discussion of the coupling phase involved.