Theory of spin wave excitations of metallic A-type antiferromagnetic manganites

The spin dynamic of the metallic A-type antiferromagnetic manganites is studied. An effective nearest-neighbour Heisenberg spin wave dispersion is derived from the double exchange model taking into account the superexchange interaction between the core spins. The result of inelastic neutron scattering experiment on ${Nd}_{0.45}{Sr}_{0.55}Mn{O}_3$ is qualitatively reproduced. Comparing theory with experimental data two main parameters of the model: nearest-neighbour electron transfer amplitude and superexchange coupling between the core spins are estimated.