Structure and magnetic properties of (La1-xFex)FeO3 (x = 0, 0.25, 0.50) perovskite

Abstract

The effect of Fe doping of a LaFeO3 orthoferrite nanostructure was investigated, and the structural and magnetic properties of the resulting material were studied. The pure (La1-xFex)FeO3 (x = 0, 0.25, 0.50) nanocrystals with a minimal amount of impurities (?6%) were successfully produced by the sol–gel technique using La(NO2)3 and Fe(NO2)·34H2O as starting materials. The phase impurities and crystalline structures were characterized through multiphase Rietveld refinement of x-ray diffraction data. The results showed that the average crystallite size of synthesized powders is ~18 nm. Lanthanum ions have a valence state of La3+ in the (La1-xFex)FeO3, meanwhile inducing the states of mixed character of Fe3+ and Fe4+ in Fe ions, as confirmed by X-ray photoelectron spectroscopy. Magnetometry measurements provided evidence that all the samples, including the parent LaFeO3, are weak ferromagnets; this finding is explained by distortions in the orthoferrite structure, which disturb the ideal antiferromagnetic coupling between Fe3+ ions. Fe substitution for La ions in the parent LaFeO3 structure leads to a significant increase in the saturation magnetization from 5.4 to 10.2 Am2 kg-1, indicating that the double-exchange interaction occurs between Fe3+ and Fe4+ ions. © 2019 Elsevier B.V.