OXYGEN DEPENDENCE OF THE TRANSPORT-PROPERTIES OF ND1.78CE0.22CUO4+ -DELTA/

We have investigated the transport properties of high-quality Nd1.78Ce 0.22CuO4+/-delta films as a function of oxygen concentration. Surprisi ngly we find superconductivity in films that are slowly cooled in vacu um from the deposition temperature. A systematic study of the effect o f oxygen on resistivity, Hall effect, and thermopower suggests that ex tra oxygen introduces impurity scattering without changing the carrier density. Magnetoresistance data reveal that these impurities are spin disordered in nature. The spin impurities introduced upon oxygenation of the sample may be responsible for suppressing the superconductivit y.