Study of electrical transport and magnetoresistive properties of La0.67−x DyxPb0.33 MnO3 (x=0.00, 0.10 and 0.15)

We investigate the influence of dysprosium (Dy) doping on the magneto-electrical properties of LPMDyx compounds. The temperature dependence of electrical resistivity shows that all samples undergo a sharp metal–semiconductor (M–SC) transition at a temperature (TM–SC), accompanying the ferromagnetic–paramagnetic transition. Metallic resistivity ρ(T)=ρ0+ρ1T2 is observed below TM–SC. Above TM–SC, the electrical conductivity is dominated by adiabatic small polaron hopping model, inducing electrical resistivity in the paramagnetic region as ρPM(T)=CTexpEakBT. A percolation theory is introduced to understand the properties of these mixed systems. We have also found that the estimated results are in good agreement with the experimental data. Above all, the magnetoresistance (MR) study showed a peak which has a great value around the metal–semiconductor (M–SC) transition temperature. The dependence of resistivity on the temperature and magnetic field data is used to deduce the magnetic entropy change.