Magnon damping by magnon-phonon coupling in manganese perovskites

Inelastic neutron scattering was used to systematically investigate the spi n-wave excitations (magnons) in ferromagnetic manganese perovskites. In spi te of the large differences in the Curie temperatures (Tc's) of different m anganites, their low-temperature spin waves have very similar dispersions w ith the zone-boundary magnon softening and broadening that cannot be explai ned by the canonical double exchange mechanism. From the wave-vector depend ence of the magnon lifetime effects and its correlation with the dispersion s of the optical-phonon modes, we argue that a strong magnetoelastic (magno n-phonon) coupling is responsible for the observed low-temperature anomalou s spin dynamical behavior of the manganites.