SPIN-CLUSTER STATES IN CUO2 PLANES

When doping the antiferromagnetically ordered high-T(c) cuprates with holes magnetic polarons (spin-polarized clusters) are formed. We discu ss two different mean-field approaches of the three-band Hubbard model to calculate the binding energy and polarization of the clusters. At higher hole concentrations and due to cluster diffusion a phase separa tion is formed by establishing large fractal or percolative clusters. This percolation picture allows us to understand experimentally obtain ed results for phase separation as well as magnetic and conductive pha se diagrams.