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

Abstract

The relation between the orbital ordering and magnetic structure of the crystal LaMnO3 is investigated. The dependence of the exchange parameters on the angle Φ of the orbital structure is determined. When the isotropic exchange interaction and the single-ion anisotropy, which depends on the angle Φ and the rotational distortions, are introduced into the spin Hamiltonian, a four-sublattice structure (AX, FY, GZ) is obtained with orientation 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 (AX ≫ GZ, FY). The effect of a magnetic field on the magnetic structure and the antiferromagnetic resonance spectrum are investigated taking account of the nonequivalent, anisotropic, orbitally-dependent g tensors. The spin-flop and spin-flip transition fields are calculated.