Enhancement in the Superconductivity of Tl(Ba2−x Mg x )(Ca1Be1)Cu3O10−δ System with the Decreased Thickness of Charge Reservoir Layer

Abstract

Mg-doped Tl(Ba2−xMgx)(Ca1Be1)Cu3O10−δ (x=0, 0.25, 0.5, 0.75) superconductors are synthesized at the normal pressure and the possible mechanism of superconductivity in these compounds is studied. Tl(Ba2−xMgx)(Ca1Be1)Cu3O10−δ samples have shown an orthorhombic crystal structure and their c-axis length decreases with Mg doping. In these studies we have investigated the role of decreased thickness of charge reservoir layer in the mechanism of superconductivity. The Tc(R=0) in as-prepared Tl(Ba2−xMgx)(Ca1Be1)Cu3O10−δ (x=00, 0.25, 0.5, 0.75) samples was 97, 99, 100, 94 K and in oxygen post-annealed samples the Tc(R=0) is observed at 100, 98, 103, 101 K, respectively. The magnitude of the superconductivity after Mg doping is improved in Tl(Ba2−xMgx)(Ca1Be1)Cu3O10−δ (x=0, 0.25, 0.5, 0.75) samples. It was observed from the FTIR absorption measurements that the phonon modes related to CuO2 planar oxygen atoms are hardened with the doping of Mg in the charge reservoir layer. These studies have shown that the thickness of charge reservoir layer decreases with Mg doping which most likely makes charge transfer mechanism more efficient, promoting increase in the magnitude of superconductivity.