Influence of processing conditions on the crystal structure and magnetic behavior of La0.7Ca0.3MnO3±δ samples

In this work we report crystallographic structure variations and the related modifications on the magnetic behavior of La0.7Ca0.3MnO3+/-delta introduced by heat-treatments in different synthesis atmospheric conditions. We have prepared polycrystalline ceramic samples using a modified polymeric precursors method, which produces highly homogeneous specimens. The use of argon atmosphere enlarges the crystalline c-axis as detected by Rietveld refinements. As a consequence, an improvement in the magnetic transition temperature T-C of the samples was observed. Our results also indicate that different heat-treatment conditions change the magnetic interactions between the ferromagnetic (F) and antiferromagnetic (AF) structures of these systems. Our conclusions rely on the use of AC magnetic susceptibility measurements as the experimental tool for measuring these variations. (C) 2003 Elsevier Science Ltd. All rights reserved.