Hopping conduction behavior with the Coulomb effects in colossal magnetoresistance materials

We report on the temperature dependence of resistivity in La 0.7-x Pr x Pb 0.3 MnO 3 (x=0, 0.5, 0.7) bulk samples in order to explore the hopping transport behavior with the Coulomb effects for the colossal magnetoresistance materials. The experimental observations in La 0.7-x Pr x Pb 0.3 MnO 3 (x=0.5, 0.7) bulk samples reveal the exponential temperature dependence of resistivity p(T) ∞ exp[(T 1 /T) n with n = 1/2, when system was the paramagnetic (PM) insulator at the high temperature range (T>Tp). Evidence for the hopping conduction with Coulomb effects is presented By using the approximate method of the VRH conduction in the localization regime base on Efros and Shklovskii model [A. L. Efros and B. I. Shklovskii, J. Phys. C, Solid State Phys. 8, L49 (1975)], the localization length of eg electrons can be estimated with the relationship, ξ=2.8e 2 /(4πe 0 κk B T 1 ). The reasonable results of localization length can be evaluated to explain the possibility of the presence of the Coulomb interactions in these CMR materials.