Superconductivity of Y1Ba2(Cu1-xFex)3Oy

Abstract

A systematic study on the superconductivity of Y₁Ba₂(Cu_1-x Fe _x )₃O _y has been made down to 30 mK for various x values. The critical temperature decreases linearly with x. The complete Meissner effect is retained down to 30 mK, up to about x=0.10. The crystal structure of the superconducting phase was found to transform from the orthorhombic to the tetragonal between x=0.02 and 0.05. It is concluded that a branching effect of a one-dimensional chain of Cu1-O through Fe impurities is essential for this structure transition. The supercurrent is considered to flow on the two-dimensional sheets of Cu2.