Spin dynamics and magnon–phonon interactions in Nd0.6Sr0.4MnO3

The magnon dispersion of Nd0.60Sr0.4MnO3 has been measured along the [q q q], [q q 0], and [0 0 q] propagation directions using inelastic neutron scattering. Modes attributed to both Mn–Mn interactions and Nd–Mn interactions were detected. At low temperatures, and for all three directions, the low q Mn–Mn dispersion closely followed a Heisenberg nearest-neighbor model calculation, before showing marked softening at higher values of q. For the [q q 0] and [0 0 q] directions, this softening appears to correspond with intersection with 20 and 40 meV phonon branches, respectively. At low temperatures, and for all three directions, the Nd–Mn dispersion followed the calculated Heisenberg dispersion for all measured points. Additionally, the temperature dependence of the magnon stiffness parameter D   was measured up to TC=273K, and showed conventional temperature renormalization behavior.