Coexistence of localized and itinerant carriers near Tc in calcium-doped   manganites
  We explore the possibility that polaronic distortions in the paramagnetic phase of La$_{0.67}$Ca$_{0.33}$MnO$_3$ manganites persist in the ferromagnetic phase by considering the observed electrical resistivity to arise from coexisting field- and temperature-dependent polaronic and band-electron fractions. We use an effective medium approach to compute the total resistivity of the two-component system, and find that a limit with low percolation threshold explains the data rather well. To test the validity of this model, we apply it to the thermoelectric coefficient. We propose a plausible mean-field model that reproduces the essential features of a microscopic model and provides a comparison with the experimental mixing fraction, as well as the magnetization and magnetic susceptibility. 
M. Jaime(1), P. Lin(2), S.H. Chun(2), M.B. Salamon(2), P. Dorsey(3),   and M. Rubinstein(3) ((1) Los Alamos National Laborat...