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

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Abstract
Diffuse neutron scattering measurements have been made on single crystals of Nd0.5Pb0.5MnO3 in the temperature range 5-295 K. It is found that Nd0.5Pb0.5MnO3 begins to order magnetically at a temperature Tc approximately=184 K, this being accompanied by an anomalous change in electrical conductivity. Above Tc the conductivity is of the activated hopping type and below Tc it is metallic. Neutron scattering measurements show that below Tc there are well defined magnon branches which soften as T approaches Tc. Temperature-dependent coherent diffuse quasi-elastic scattering occurs around some Bragg peaks above Tc. 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.