ANTIFERROMAGNETISM AND PHASE-SEPARATION IN ELECTRONIC MODELS FOR DOPED TRANSITION-METAL OXIDES

We investigate the ground state properties of electronic models for do ped transition-metal oxides. An effective t-J like Hamiltonian is deri ved from the case of strong Hund coupling between the conduction elect rons and localized spins by means of the projection technique. An attr active interaction for conduction electrons and an antiferromagnetic c oupling of the localized spin are obtained. A large ratio of the attra ction to effective electron hopping, which is modulated by the spin ba ckground, will lead to the phase separation. The antiferromagnetic pha se and the phase separation appear in the case of either high or low d ensity of electrons. The possible relevance of the phase separation to the charge stripe phase in doped transition-metal oxides is discussed . [S0163-1829(98)51238-6].