Conduction mechanism in La0.67Ba0.33Mn1-xFexO3 (x=0-0.2) perovskites

International audience ; We have investigated the mechanism of conduction in relatively high iron doped manganites La0.67Ba0.33Mn1-xFexO3 (0 <= x <= 0 2) Below 10% of Fe3+ content these materials show metal-semiconductor transition with a peak of resistivity (rho(max)) at a temperature T-P, whereas above 10% of Fe3+ concentration they exhibit only semiconductor behaviour Interestingly T-P for the undoped compound is very close to room temperature (297 K) and decreases with doping rates (230 and 114 K for x = 0 05 and 0.1, respectively) Low temperature resistivity (rho) data below T-P have been relatively well fitted with the relation rho(T) = rho(0) + rho T-2(2) + rho(4) T-5(4) (5), indicating the importance of grain/domain boundary, electron-electron scattering effects and to a lesser extent electron-(magnon, phonon) scattering effects in the conduction of these materials. On the other hand the high temperature resistivity data (T > T-P) were explained using variable range hopping (VRH) and small polaron hopping (SPH) models Changes in resistivity variation have been analysed on the basis that the substitution of Fe3+ for Mn3+ reduces the number of available hopping sites for the Mn e(g) (l) electron and suppresses the double exchange (DE), rather than on the basis of lattice effect which is insignificant due to similar ionic radii of Fe3+ and Mn3+ (C) 2009 Elsevier B V. All rights reserved.