Two new electron cuprate superconductors, Pr1.85Th0.15CuO4−y and Eu1.85Ce0.15CuO4−y, and properties of Nd2−xCexO4−y

Abstract We report the first observation of superconductivity in the Pr 2− x Th x CuO 4− y and Eu 2− x Ce x CuO 4− y systems. Superconducting resistive onset temperatures of ∼ 23 K and ∼ 13 K were observed for Pr 1.85 Th 0.15 CuO 4− y and Eu 1.85 Ce 0.15 CuO 4− y , respectively; the corresponding transition midpoints are T 0.5 c = 19.5 and 8 K . Magnetic susceptibility data indicate that the superconductivity is a bulk property. Transition temperatures higher than previously reported for Pr 1.85 Ce 0.15 CuO 4− y and Sm 1.85 Ce 0.15 CuO 4− y were also observed. Oxygen content analysis reveals that the superconducting Ce-doped specimens have quite small oxygen deficiencies. Specific heat data for Nd 2 CuO 4− y ( y ≈0.07) and Nd 1.85 Ce 0.15 CuO 4− y ( y ≈0.02) display a large peak, presumably associated with magnetic ordering of Nd 3+ ions, Which decreases in magnitude with Ce doping. Pressure-dependent electrical resistivity measurements reveal an increase of T c with applied pressure for Nd 1.85 Ce 0.15 CuO 4− y ( y ≈0.02), at a rate of approximately d T c /d P ≈0.025 K/kbar.