Magnetism and Jahn-Teller effect in LaMnO3

Combining charge transfer with the Jahn-Teller electron-phonon coupling, the magnetic properties of LaMnO3 and the influence of the Jahn-Teller effect are studied. The interaction parameters of super exchange coupling between manganese spins are obtained. In the ground state, manganese spins are antiferromagnetically ordered but canted by a small angle. The spectrum of the low-energy spin excitation is very close to that observed experimentally. Behaviors of magnetization and spin correlation functions of LaMnO3 exhibit certain two-dimensional ferromagnetic characters, even though it is an A-type antiferromagnet with anisotropic super exchange coupling. These results agree with several experiments. Furthermore, it is expected that the super exchange interactions depend on the electron-phonon coupling strength exponentially, and the Neel temperature will exhibit isotope shift. (C) 1998 American Institute of Physics.