Magnetic and electrical behaviour of La0.67Ba0.33Mn1-xFexO3 perovskites

(La0.67Ba0.33)Mn1-xFexO3 manganites compounds have been prepared by doping up to 20% of Fe at the Mn site. As previously reported in the literature paramagnetic (PM) to ferromagnetic (FM) phase transition has been observed in materials with low Fe doping (<= 10%). In our x = 0 and x = 0.05 compounds the Curie temperature (T-C) is close to room temperature. Above 10% Fe amount, specimens exhibit a glass magnetic behaviour with a spin- or cluster-like freezing process that can be related to a loss of ferromagnetic double exchange interaction. Below 10% of Fe3+ doping electrical-resistivity measurement shows metal - semiconductor transition with a maximum peak of resistivity (rho(max)) at a temperature T-P close to T-C. Above 10% of Fe3+ doping amount the materials exhibit only semiconductor behaviour. Both T-C and T-P decrease with doping rates with an increasing difference in temperature (T-P, being lower than T-C). Results are consistent with a reduction of the number of available hopping sites for the Mn e(g)(up arrow) electron due to substitution of Mn3+ by Fe3+ that suppress the double exchange (DE) interactions. (C) 2009 Elsevier B.V. All rights reserved.