Superconductivity of (La1−xSrx)2CuO4−γ (0≦χ≦0.03)

Abstract The dependence of the fractional volume of an apparent superconductor, its transition temperature and paramagnetic susceptibility on the strontium concentration χ is studied in (La 1−x Sr x ) 2 CuO 4−θ for the small region of χ (0 ≦χ≦0.03). Superconductivity observed in undoped La 2 CuO 4−γ compound disappears at χ = 0.01 together with the disappearance of the antiferromagnetic phase. The origin of this superconductivity is discussed taking account of the anomalous property, i.e., the Meissner effect is larger than the shielding effect. The phase diagram of (La 1−x Sr x ) 2 CuO 4−γ is interpreted from a phenomenological crude model based on weakly localized holes around oxygen sites in the CuO 2 plane.