ELECTRONIC PHASE-SEPARATION IN LA-CUPRATES - ON THE ROLE OF HOLE AND OXYGEN DIFFUSION

The mechanisms driving the phase separation in high-T(c) 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 less-than-or-equal-to T less-than-or-equal-to 170 K 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 T(c) values becomes superconducting. Above 180 K the cluster motion becomes unrestricted in space and a more extended subphase is built up, however, with lower T(c) values. Above approximately 230 K oxygen diffusion starts leading to an unexpected destruction of the conducting/superconducting phase.