EXCESS OXYGEN DOPING IN SINGLE-CRYSTALS OF LA2-XBIXCUO4-SEPARATION(DELTA WITH OR WITHOUT MACROSCOPIC PHASE)

Systematic heat treatments have been performed using single crystals o f La2-xBixCuO4+delta to study the effect of oxygen doping on the phase stability as well as the three-dimensional magnetic order. For La2CuO 4+delta, the analysis of magnetic susceptibility peak near the Neel te mperature T-N revealed that the continuous decrease of T-N upon doping is terminated at 280 K. The further doping additionally induces the p reviously reported macroscopic phase separation accompanying an antife rromagnetic phase with T-N = 265 K and a superconducting one with T-C less than or equal to 35 K. On the other hand, for La2-xBixCuO4+delta with x similar to 0.05 no macroscopic phase separation was observed up to delta approximate to 0.02. Upon the oxygen doping, the T-N continu ously decreases from 310 K to below 10 K only by the heat treatment. T he scaling behavior of magnetic ssusceptibility previously studied by the powder sample of La(2-x)SrxCuO(4+delta) was reexamined in this sys tem.