We investigate the electronic correlation effect on the ground-state properties of the double-exchange model for manganites by using a semiclassical approach and the slave-boson technique. It is shown that magnetic field has a similar effect on the canted angle between manganese spins as doping concentration does, and the canted angle exhibits weak dependence on the Coulomb interaction. The possibility of phase separation in the present model is also discussed. In the slave-boson saddle-point

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... proximation in the ferromagnetic metallic regime, the dependence of the magnetization and the Curie temperature on the doping concentration exhibits maxima near 1/3 doping. These results agree with experimental data and suggest that the electronic correlation plays an important role for understanding the ground-state properties of manganites.