Determination of the exchange anisotropy in perovskite antiferromagnets using powder inelastic neutron scattering

A procedure is outlined for the determination of magnetic exchange constants in anisotropic perovskite anitferromagnets using powder inelastic neutron scattering. Spin-wave densities of states are measured using time-of-flight inelastic neutron scattering for LaMnO₃ (A-type antiferromagnet), LaVO₃ (C type), and LaFeO₃ (G type) and compared to Heisenberg model calculations. The anisotropy of in-plane (J_ab) and out-of-plane (J_c) exchange constants can be obtained from the data. The procedure quickly determines the magnetic exchange interactions without the need for single-crystal dispersion measurements and allows for rapid systematic studies of the evolution of magnetism in perovskite systems.