Enhancement of Tc, orthorhombicity and AC magnetic shielding in argon preheated HTC superconductor (Y1−xSmx)(SrBa)Cu3O6+z

Abstract

We report in this paper on the preparation, X rays diffraction, AC magnetic compound measurements and the effect of heat treatments in (Y1−xSmx)(SrBa)Cu3O6+z (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1). Each sample was subjected to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. For each x value, the [AO] treatment increases the orthorhombicity ϵ = (b−a)/(b+a) (for 0≤ x ≤ 1), Tc (for x ≥ 0.4) and the distance d[Cu(1)-(Sr/Ba)] for x < 0.5. When x increases from 0 to 1, ϵ decreases with Tc[O]. However, Tc[AO] decreases with ϵ until x = 0.2 and after it increases by 6 K to 85 K for x = 1 [AO]. A remarkable improvement in the shielding effect S, in the case of the samples [AO] at all T < Tc and for any applied field, was observed for x > 0.5 indicating an improvement in the pinning properties. Remarkable correlation was observed between Tc(x) and the number psh(x) of holes by Cu(2)-O2 superconducting planes. So the structural, magnetic and superconducting properties are correlated with the effect of argon heat treatment. A combination of several factors such as decrease in d[Cu(1)-(Sr/Ba)]; increase in cationic and chain oxygen ordering; psh and in-phase purity for the [AO] samples may account for the observed data.