Abstract
The relationship between electrical and magnetic properties of manganites has been traced through the analysis of dependence of La0.47Eu0.2Pb0.33MnO3(LEPMO) and La0.47Y0.2Pb0.33MnO3(LYPMO) resistivity on temperature. The dependence of electrical resistivity on temperature shows a metal-semiconductor transition at T(M-Sc)and a decrease in T(M-sc)with Eu and Y substitution. The critical property of both systems around second order transition was investigated using Fisher-Langer relation and Suezaki-Mori method. The obtained exponents values from resistivity were so close to those predicted by the 3D-Ising model. These results and the analysis of the critical exponents from magnetization measurements were in good agreement. For low temperatures (T < TM-Sc), the electrical conduction process obeys the Scattering model defined by rho(T)=rho(0)+rho T-2(2)+rho T-5(5). While forT > TM-Sc, for the two samples, the mechanism of electrical conduction is governed by the thermal activation model defined by rho = rho(0)Texp(E-a/k(B)T). In order to understand the transport mechanism in the whole temperature range, the phenomenological percolation model, based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, was used in fitting the electrical resistivity. Therefore, it was found that the estimated values of the resistivity are in good agreement with experimental data. Magnetoresistance study showed a peak that has a great value around the transition temperature (TM-Sc).