T_c of Overdoped RBa₂Cu₃O_y+Δy(R=Ln and Y)

Abstract

For RBa₂Cu₃O_y(R=Ln and Y), the relationship between superconducting transition temperature T_c, overdoping oxygen content Δy, and R was obtained through studies of oxidation under pressure. T_c of RBa₂Cu₃O_y remains almost unchanged through various levels of overdoping for small inonic radii of R. As the ionic radius of R increases, T_c decreases with the level of overdoping. The decrease changes systematically from Eu to La; the decrease for La is the steepest. This general view is somewhat modified by the temperature of overdoping. Overdoped oxygen seems to settle down on CuO and/or the Y plane depending also on the treating temperature.