Magnetic and superconducting properties of the electron-doped compounds Ln2−xMxCuO4−y (Ln = Pr, Nd, Sm, Eu, Gd: M = Ce, Th)

Abstract The variations in transport and magnetic properties as a function of annealing conditions are discussed for the Ln 2−x M x CuO 4−y compounds. A composition x∼0.15−0.16 and a small oxygen deficiency (y∼0.02) are required to optimize superconducting properties. For Nd 1.85 Ce 0.15 CuO 3.98 , critical current densities, inferred from magnetization measurements, are estimated to be as high as 10 6 A/cm 2 at 4.2 K in zero field. From resistive measurements of polycrystalline samples in fields up to 8 tesla, upper critical field H c2 slopes of −dH c2 /dT∼1.5T/K are obtained at low temperatures.