Percolative phase separation in La₂CuO_4+δ and La_2-xSr_xCuO₄

We report on the formation of conducting phases in slightly doped La2CuO4 samples by the existence of a percolative phase separation. Phase separation can be quenched by rapid cooling and can be restored by the application of a 3 T magnetic field. Magnetically polarizable quasiparticles are shown to be formed by hole doping which fuse to form percolative conducting and below 37 K superconducting phases. © 1992 Springer-Verlag.