Polycrystalline samples of La5/8-yPr yCa3/8MnO3; 0 <; y <; 0.625; were synthesized by the solid-state reaction method and studied by several techniques including electrical resistivity rho(T, H) measurements. The occurrence of an insulator-to-metal transition was observed for all samples at a temperature T MI, and for samples with y > 0.35 a transition to a charge and orbital-ordered state was also observed. The rho(T, H) data analyses suggest the coexistence of at least two ordered phases in these samples: a ferromagnetic metallic phase FMM and a charge and orbital-ordered insulating COI phase.The data also indicate that the volume fraction of these phases can be changed by the variation of thermodynamic parameters like temperature T and magnetic field H. The magnetoresistance MR(T) determined from rho(T, H) data were observed in a large temperature range for all samples. In addition, samples with y > 0.35 were found to display a pronounced colossal magnetoresistance effect due to a severe competition between FMM and COI coexisting phases.
manganites; (La,Pr)CaMnO3; colossal magnetoresistance
