The effect of the annealing temperature on the structural and magnetic properties of the manganites compounds

The electron-doped manganites La1-xCexMnO3 (x = 0.3, 0.4 and 0.5) compounds were prepared by the sol-gel method and annealed at two different temperatures of 1400 degrees C and 900 degrees C. The morphology, crystallographic and magnetic properties of these compounds were studied as function of annealing temperature. The morphology study shows a decrease of the grain size for the temperature of 900 degrees C. The grain size is found to affect the structure which is confirmed by the Rietveld refinements of X-ray diffraction revealing a transition from the orthorhombic phase to the rhombohedral one when decreasing the annealing temperature from 1400 degrees C to 900 degrees C. This transition is accompanied by an enhancement of the one-electron bandwidth inducing an increase of the magnetization and the Curie temperature. The magnetocaloric study indicates the existence of a transition from second to first order when decreasing annealing temperature from 1400 degrees C to 900 degrees C. (C) 2008 Elsevier B.V. All rights reserved.