Electrical transport and giant magnetoresistance in La0.8-x□xCa0.2MnO3 (X=0, 0.1 and 0.2) oxides

La0.8-x square xCa0.2MnO3 (x =0, 0.1 and 0.20) samples were prepared by the conventional solid-state reaction and annealed at 1200 K. X-ray diffraction and scanning electron microscopy were used to check the crystalline structure and the samples morphology. Resistivity measurements versus temperature under different magnetic fields are performed to investigate the electronic transport as well as the magnetoresistance properties. A classical metal-insulator transition at T-MI is observed for all samples. As other results, the increase of the lanthanum deficiency content induces the decrease of the resistivity values. In addition, a resistivity minimum has been observed for all samples in the range of temperatures from 5 to 50 K, which is strongly influenced by an applied magnetic field. Therefore, the electrical resistivity is fitted with the phenomenological percolation model which is based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. Magnetoresistance measurements show high values which reach 76% for x=0.1 sample. (C) 2014 Elsevier B.V. All rights reserved