Investigation of the electronic structure of the charge-ordered phase in epitaxial and polycrystalline La1-xCaxMnO3 (x = 0.55, 0.67) perovskite manganites

In this work, the charge transport properties of charge-ordered (CO) La(1-x)Ca(x)MnO(3) (x=0.55, 0.67) epitaxial thin films and polycrystals are discussed following the recent controversy of localized electron states versus weakly or delocalized charge-density wave states in CO manganites. The transport properties were investigated by current versus voltage, direct current resistivity versus temperature, local activation energy versus temperature, magnetoresistance, and alternating current admittance spectroscopy measurements, which all indicated a localized electronic structure in the single CO phase. Delocalized charge anomalies previously observed may be restricted to phase separated materials.