Effect of Fe Substitution on Superconductivity and Flux Pinning of Bi-2212 Single Crystal

Abstract

The superconductivity and flux pinning of Fe-substitued single crystals of Bi-2212 have been studied by SQUID. The Fe-substitution in the single crystals voilently depresses the superconducting transition temperature of the crystals. The content and the homogeneity of superconducting phase in the Bi-2212 single crystals decrease with increasing Fe content in the crystals. The rate of Tc decrease with Fe-substitution in the crystals is as high as 15 K/(Fe/(Cu+Fe))at.% for the as-grown crystals of Bi2.1Sr1.9Ca1(Cu1-yFey)2O8+δ with a nominal Fe content from y=0 to y=0.01, while it is only 7.3 K/(Fe/(Cu+Fe))at.% for the as-grown crystals with Fe content from y=0.01 to y=0.03. A small amount of Fe-substitution (y<0.01) increases the Jc and the flux pinning of the as-grown Bi-2212 crystals. The Fe-substitution is a kind of effective pinning center in the Bi-2212 crystals. The irreversible field shifts towards lower field with increase of Fe-substitution in Bi-2212 crystals.