SPIN-POLARON FORMATION AND PHASE-SEPARATION

We study the formation of spin-polarized states within the three-band tJ-model which corresponds to the large U-limit of the Emery model. It turns out that in the three-band model these states are already stabi lized in the relevant parameter regime whereas in the one-band tJ-mode l spin-polarized states are only formed for unphysically small values of J/t. Following the concept of microscopic percolative phase separat ion we further study the properties of inhomogeneous spin-polarized su bstructures upon doping. As a simplest model the doping-dependent pola rization of a stripe in the (11)-direction is investigated. To treat t he distribution of cluster states more generally the CPA method is use d. The results allow a description of the insulator-metal transition a s an overlap of spin-polaronic wave functions forming thus a connected network of cluster states.