Correlation Between Enhanced ${\rm T}_{\rm c}$, AC Magnetic Irreversibility Line and Heat Treatment in High ${\rm T}_{\rm c}$ Superconductors

Essediq Youssef El Yakoubi,Jamal Hemine,Hassan Chaib,Abdelhakim Nafidi,Ramanathaan Suryanarayanan,Mohamed Braigue,Thami El Gouti,M Srinivasa Vinod,Redwane Morghi

doi:10.1109/tasc.2010.2088371

Abstract

We report here on the preparation, resistivity, AC magnetic susceptibility measurements and effect of heat treatments in (Y 1-x Sm x )(SrBa)Cu 3 O 6+z . Each sample was subject to two type of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. An enhancement of T c [AO] was observed for x ≥ 0.4. In the normal state, the [AO] treatment reduced the linear resistivity parameters indicating a diminution of the interaction of carrier charges with phonons. Tc (χ ' ) and Tc (ρ = 0) were in good agreement. An enhancement of the AC irreversibility line H ( t = Tp / Tc ) was observed due to [AO] treatment for x >; 0.5 indicating an improvement in the pinning properties. The data were analysed with the relation H = K ' (1- t ) n . Remarkable correlations were observed between δ Tc ( x )= Tc [ AO ]- Tc [ O ] and δ K ' ( x ); and between Tc ( x ) , d [ Cu (2)- Y / Sm ]( x ) distance and the number psh ( x ) of holes by Cu(2)-O 2 superconducting planes. A combination of several factors such as decrease in d [ Cu (1)-( Sr / Ba )] for x >; 0.4; increase in cationic and chain oxygen ordering; p sh and in-phase purity for the [AO] samples may account for the observed data.

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