Neutron scattering and electrical transport in Nd0.5Pb0.5MnO3

Diffuse neutron scattering measurements have been made on single crystals of Nd 0.5 Pb 0.5 MnO 3 in the temperature range 5-295 K. It is found that Nd 0.5 Pb 0.5 MnO 3 begins to order magnetically at a temperature T c approximately=184 K, this being accompanied by an anomalous change in electrical conductivity. Above T c the conductivity is of the activated hopping type and below T c it is metallic. Neutron scattering measurements show that below T c there are well defined magnon branches which soften as T approaches T c . Temperature-dependent coherent diffuse quasi-elastic scattering occurs around some Bragg peaks above T c . This diffuse scattering is magnetic in origin and its energy width is consistent with the activation energy derived from the conductivity, suggesting magnetic polaron formation. Diffuse scattering due to lattice polarons has not been observed.