Double-exchange model: phase separation versus canted spins

We study the competition between different possible ground states of the do uble-exchange model with strong ferromagnetic exchange interaction between itinerant electrons and local spins. Both for classical and quantum treatme nt of the local spins the homogeneous canted state is shown to be unstable against a phase separation. The conditions for the phase separation into th e mixture of the antiferromagnetic and ferromagnetic/canted states are give n. We also discuss another possible realization of the phase-separated stat e: ferromagnetic polarons embedded into an antiferromagnetic surrounding. T he general picture of a percolated state, which emerges from these consider ations, is discussed and compared with results of recent experiments on dop ed manganaties.