Specific features of magnetic structure formation in orbitally degenerate BiMnO{sub 3} manganite

The orbital structure and magnetic ordering of the Jahn-Teller multiferroic BiMnO{sub 3} manganite have been theoretically studied. It is shown that the orbital structure depends not only on the nearest-neighbor oxygen environment of manganese ions, but also on their next-to-nearest neighbors. The orbital structure significantly influences the magnetic order that forms as a result of competition between ferromagnetic and antiferromagnetic exchange interactions.