Intra- and interatomic direct exchange competition and canted magnetic structure in Heisenberg model

A simple exactly solvable model for the formation of a canted magnetic structure in a system of crystallographically and chemically equivalent magnetic atoms is suggested. It is shown that a pair of atoms, in which the exchange integrals between orbitals of different types, localized on the neighboring centers, have opposite signs and are close in magnitude, is not described by a model with the single interatomic exchange parameter. In this case, only via the competition between intra- and interatomic exchange interactions is the canted magnetic structure realized where the angle between the sublattice moments can take any value between 0 and ππ.