We have measured the temperature dependence of the resistance for a La2CuO4+ single crystal at pressures from 1 bar to 18 kbar. The effects of pressure on the antiferromagnetic transition temperature TN and the superconducting transition temperature Tc are compared to those of oxygen doping. © 1989 The American Physical Society.

We have determined the structure of the newly discovered electron-doped superconductor Nd1.85Ce0.15CuO4- at 11 and 300 K using high-resolution neutron-powder-diffraction techniques. Both nonsuperconducting oxygenated and superconducting Zr-gettered (Tc=24 K with shielding and Meissner fractions of 30 and 16% at 5 K, respectively) samples were investigated to study the effect of Zr gettering on the crystal structure and oxygen stoichiometry. We find that the structure remains tetragonal (I4/mmm), with no evidence for Nd/Ce ordering, for both samples at both temperatures. Structure and oxygen stoichiometry of the oxygenated and Zr-gettered samples remain remarkably similar at both temperatures, the only difference being a slight decrease (but greater than three standard deviations) in the thermal parameters of the rare-earth ions along the c axis for the superconducting sample. Thermogravimetric analyses confirm the oxygen stoichiometry determined from the structural refinements. © 1989 The American Physical Society.