Spin dynamics of magnetoresistive oxides

A review is given of the neutron scattering measurements of the spin dynamics of the magnetoresistive oxides. A number of anomalous features have been identified in the manganites, including very strong damping of the spin waves in the ground state and as a function of temperature, anomalous spin wave dispersion and the development of a strong spin-diffusion component to the fluctuation spectrum well below T-C in the region of optimal doping. For the Tl2Mn2O7 pyrochlore, on the other hand, the behavior of the spin dynamics is conventional, which argues that the mechanism responsible for the magnetoresistive effect has a different origin in these two classes of materials.