  The spin-wave spectrum in the metallic ferromagnetic lantha-num cubic
manganites was investigated. The interactions with four coordination spheres
(32 neighbors) were taken into ac-count. The Heisenberg superexchange between
all manganese ions as well as double exchange between the manganese ions with
different valence were under consideration. The obtained magnon spectrum
permits to investigate dispersion relations along an any crystallographic
directions. This possibility was used for the numerical evaluation of the
exchange parameters in the compounds La0.75Ca0.25MnO3 and La0.70Ca0.30MnO3 from
the inelastic neutron scattering data.
