RE dependence of superconductivity in parent T′-RE2CuO4

We present the results of our systematic investigation of the RE dependency of superconductivity in the parent compounds T′-RE2CuO4 (RE = Pr, Nd, Sm, Eu, Gd, and Tb). Superconductivity with a transition temperature (Tc) ≥ 30 K is achieved for RE = Pr and Nd by the metal organic decomposition (MOD) method. By contrast, Tconset is at highest 20 K for RE = Gd. A stringent control of synthesis- and post-annealing-conditions is required to obtain superconducting films. Our results indicate that the induction of superconductivity into T′-RE2CuO4 cuprates strongly depends on the RE3+ ionic size. This trend is discussed from the viewpoint of RE-dependent thermodynamic stability of T′-RE2CuO4. For smaller RE3+ ions, the thermodynamic boundary conditions become tighter.

► Superconductivity has recently achieved in the parent compounds, T′-RE2CuO4 (RE = Pr, Nd, Sm, Eu, Gd, and Tb) that have for a long time been believed to be a Mott insulator. ► By metal organic decomposition, Tconset⩾30K is achieved for RE = Pr and Nd. ► By contrast, Tconset is at highest 20 K for RE = Gd, and Tb2CuO4 does not show superconductivity. ► Systematic RE dependency of superconductivity in the parent compounds can be explained by the RE-dependent thermodynamic stability of T′-RE2CuO4.