Excess Oxygen Doping in Single Crystals of La_2-xBi_xCuO_4+δ with or without Macroscopic Phase Separation

抄録

Systematic heat treatments have been performed using single crystals of La_2-xBi_xCuO_4+δ to study the effect of oxygen doping on the phase stability as well as the three-dimensional magnetic order. For La₂CuO_4+δ, the analysis of magnetic susceptibility peak near the Neel temperature T_N revealed that the continuous decrease of T_N upon doping is terminated at 280K. The further doping additionally induces the previously reported macroscopic phase separation accompanying an antiferromagnetic phase with T_N=265K and a superconducting one with T_C≤ 35K. On the other hand, for La_2-xBi_xCuO_4+δ with x-- 0.05 no macroscopic phase separation was observed up to δ ≈ 0.02. Upon the oxygen doping, the T_N continuously decreases from 310K to below 10K only by the heat treatment. The scaling behavior of magnetic ssusceptibility previously studied by the powder sample of La_2-xSrxCuO_4+δ was reexamined in this system.