Electronic phase separation in La-Cuprates - On the role of hole and oxygen diffusion

The mechanisms driving the phase separation in high-Tc La cuprates is studied by magnetic susceptibility and electrical resistivity measurements. The experiments are performed under different thermal treatment. Three temperature ranges can be resolved characteristic for different physical processes: At 150≦T≦170K a space limited diffusion of superparamagnetic clusters (single hole clusters) occurs leading to the formation of a small but rather tight percolative subphase which at high Tc values becomes superconducting. Above 180 K the cluster motion becomes unrestricted in space and a more extended subphase is built up, however, with lower Tc values. Above ≈ 230 K oxygen diffusion starts leading to an unexpected destruction of the conducting/superconducting phase. © 1993 Springer-Verlag.