Magnetoresistive properties of cerium doped La0.7Ca0.3MnO3 manganites

Abstract In this work, the effect of doping by tetravalent Ce 4+ on the structural and magnetoresistive properties of La 0.7− x Ce x Ca 0.3 MnO 3 polycrystalline manganites is presented. Samples with x= 0, 0.1, 0.2 and 0.3 are prepared by solid state reaction method and characterized. For all doping levels, the X ray diffraction ( XRD ) analysis shows that the doping element is not completely soluble in the manganite. The cell parameters values, which decrease with Ce content, are refined in the orthorhombic system by taking into account the unreacted CeO 2 phase. The observation by scanning electron microscopy ( SEM ) reveals a change in the morphology of the grains and the porosity of the samples by doping. The temperature dependence of magnetization curves shows a transition from paramagnetic to ferromagnetic state in all samples. A decrease of the Curie temperature T c with doping is revealed. The resistivity of the samples increases with Ce content and shows a clear metal to insulator transition when measured as a function of temperature. The doping also decreases the temperature T p of this transition, in accordance with the evolution of T c values. The calculated magnetoresistance ( MR ) for a magnetic field of 5 T increases gradually from 39.52% for x =0 to 66.18% for x =0.3.