Magnetic, Raman and Mossbauer properties of double-doping LaFeO3 perovskite oxides

The La0.8Ca0.2-xPbxFeO3 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) compounds were prepared by the sol-gel method using the citric acid route. The structural study revealed that all samples crystallized in the Pnma orthorhombic structure with the apparition of Ca2Fe2O5 and Fe3O4 secondary phases for samples with x >= 0.05, confirmed by the Raman spectroscopy study. The fitted Mossbauer spectra exposed, for x = 0.00 sample, the presence of a one sextuplet, related to the Fe3+ ion in the tetrahedral site, and a doublet. However, for x > 0.00 samples, the fit results showed the apparition of other sextuplets related to the Fe3O4 phase. The percentage of this latest phase was found to increase and to reach a maximum for the x = 0.10 sample and to decrease after for x = 0.15 and 0.20 samples. The variation of the magnetization (M) as a function of the temperature (T), under an applied magnetic field of 0.05 T, showed the presence of a ferromagnetic-paramagnetic transition. The magnetic study exposed that the magnetization decreases first for x <= 0.10 samples and then increases for the two other samples. This behavior was related to the competition between the Fe3+-Fe3+ tetrahedral ferromagnetic interactions and the octahedral antiferromagnetic ones between Fe3+ and Fe2+ ions. (C) 2014 Elsevier B.V. All rights reserved.