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 ϱ ( T ) ∞ exp [( T 1 / T ) n ] with n = 1/2, when system was the paramagnetic (PM) insulator at the high temperature range (T>T p ). 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 e g electrons can be estimated with the relationship, ξ=2.8 e 2 /(4πε 0 κ k 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. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)