Figure 1: Superconducting properties of PLCCO samples.

(a) A typical phase diagram for a hole-doped cuprate La2−xSrxCuO4. The AFM, superconducting and spin-glass phases are denoted by AFM, SC and SG, respectively. (b) Critical temperatures (Tc’s) determined from the resistivity of PLCCO single crystals annealed by the conventional method reported by Sun et al.26 (open triangles). (c) Schematic description of the protect annealing method. (d) The same plot as a. (e) The same plot as b for protect-annealed single crystals reported by Adachi et al. (open circles, T. Adachi et al., unpublished. Tc was determined from magnetic susceptibility measurements. (f) Magnetic susceptibility of a protect-annealed PLCCO single crystal (x=0.10) which shows the Tc of 27.0 K.