Antiferromagnetic resonance spectrum in LaMnO3: Interrelation of the orbital structure and the magnetic properties

The relation between the orbital ordering and magnetic structure of the cry stal LaMnO3 is investigated. The dependence of the exchange parameters on t he angle Phi of the orbital structure is determined. When the isotropic exc hange interaction and the single-ion anisotropy, which depends on the angle Phi and the rotational distortions, are introduced into the spin Hamiltoni an, a four-sublattice structure (A(X) , F-Y , G(Z)) is obtained with orient ation of the magnetic moments of the sublattices near the long axis of the orthorhombic cell of the crystal in the basal plane of the crystal (A(X) mu ch greater than G(Z) , F-Y). The effect of a magnetic field on the magnetic structure and the antiferromagnetic resonance spectrum are investigated ta king account of the nonequivalent, anisotropic, orbitally-dependent g tenso rs. The spin-flop and spin-flip transition fields are calculated. (C) 2000 MAIK "Nauka/Interperiodica".