We present a mean-field theory of charge, orbital, and spin ordering in man
ganites at 50% and 0% dopings, by considering Jahn-Teller interaction, near
est-neighbor repulsion, and no single-site double occupancy. For spinless f
ermions, we show that Jahn-Teller distortion and charge-orbital ordering oc
cur simultaneously. In our two-dimensional model at 50% doping, for small n
earest-neighbor repulsion the system is orbitally polarized while for large
r repulsion the system undergoes CE type ordering. As for the 0% doping cas
e, the ground state is orbitally antiferromagnetic. Upon including spin deg
ree of freedom, at both 50% and 0% dopings the ordering remains the same at
small antiferromagnetic coupling between adjacent core spins.