Rare earth ion size effect in the rates of suppression of the T<inf>c</inf>'s of the 'RE-123' high-temperature superconductors due to magnetic ion substitution into the Cu(2) sites

Abstract

The observed dependences of the rates of suppression of the Tc's due to the substitution of magnetic transition metal (TM2+) ions into the Cu(2) sites of the 'RE-123' high-temperature superconductors (HTSCs) on the size of the rare earth ions are studied within the framework of a (d+s)-wave symmetry description of the order parameters in these superconductors. It is assumed that the orthorhombic distortions which occur in these HTSCs induce a modification in the pairing potential responsible for superconductivity (the exchange of spin fluctuations) in the originally tetragonal HTSC. It is found that the rate of suppression of Tcdue to magnetic ion substitution into the Cu(2) sites depends on the orthorhombicity D=(b-a)/a of these HTSCs, the orthorhombicity being in turn dependent on the rare earth ion size.