  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 LaMnO$_{3}$ ($A$-type antiferromagnet),
LaVO$_{3}$ ($C$-type), and LaFeO$_{3}$ ($G$-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.
