This work is devoted to the description of the orbital and magnetic structu
res of pure and charge-ordered manganites, caused by crystal and charge str
uctures and the Jahn-Teller effect. The model under consideration is based
on the orbital dependency of the magnetic interactions in Jahn-Teller cryst
al. The orbital structure is considered dependent upon the Jahn-Teller dist
ortions of the coordination of the Mn3+ ions and upon the crystal field. It
is shown that exchange interactions forming the magnetic structure of the
charge-ordered manganite could be described in the superexchange approximat
ion because of localization of the charge carriers. For pure manganite and
for charge-ordered phase, the exchange parameters dependencies and the sing
le-ion anisotropy dependency, upon the angle of orbital states mixing, are
drawn. Therefore, it is shown that the orbital structure of the charge-orde
red phase is formed mainly by cooperative Jahn-Teller distortions and, taki
ng into account the charge superstructure, causes the non-trivial magnetic
structure. (C) 2001 Elsevier Science B.V. All rights reserved.