Probing anisotropic magnetotransport in manganese perovskites using Raman spectroscopy

We report an electronic Raman scattering study of the colossal magnetoresistance (CMR) manganese perovskites as a function of temperature, magnetic field, symmetry, and doping. The low-frequency electronic Raman spectrum in the paramagnetic-insulating phase of these materials is characterized by a diffusive Raman-scattering response, while a nearly flat continuum response is observed in the ferromagnetic-metallic state. We found that the (Formula presented)-symmetry electronic scattering intensity is significantly reduced with applied magnetic field near (Formula presented) in a manner reminiscent of the dc magnetoresistivity. The strongly field-dependent scattering rate in the (Formula presented) channel appears to reflect the highly field-dependent mobility along the Mn-O bond direction expected in the double exchange mechanism. In addition, we observe a persistent field dependence in the (Formula presented) electronic scattering response for (Formula presented) suggesting that the ferromagnetic phase is inhomogeneous, perhaps consisting of both metallic and insulating components.