CHARGE-ORDERED CE-TYPE AND A-TYPE STATES IN HALF-DOPED MANGANITES

According to the characteristics of the magnetic structures of the CE phase and the A phase for half-doped manganites, a two-dimensional model based on double exchange via degenerate eg orbitals as well as the Coulomb interaction and the superexchange interaction has been proposed to discuss the two phases on an equal footing. It is explained why the CE phase is usually easier to be realized for many half-doped manganites, while the A phase occasionally occurs. Moreover, our numerical calculations show that the two phases at x = 0.5 are not spin-canted, which is in good agreement with experimental observations.