Spin dynamics of La0.7Ba0.3MnO3 -: art. no. 214408

We have done inelastic neutron scattering investigations of the magnetic excitations in the ferromagnetic La0.7Ba0.3MnO3 which shows colossal magnetoresistance (CMR) behavior close to T(C)approximate to350 K. We have measured the dispersions of the spin waves along [100] and [110] and also their temperature dependence. We have fitted the dispersions with an effective localized spin model to get the nearest-neighbor exchange interaction. We have shown that the effective localized spin model is no longer valid for larger momentum transfer close to the zone boundary at which the spin-waves show softening. Also the spin-wave energy widths are found to be much larger than the instrumental resolution. We argue that the spin-wave softening and damping are generic to the double-exchange ferromagnet including those with large T-C.