Structure and magnetic properties of (La1-x Fe x)Fe O3(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 )center dot 34H(2)O 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 similar to 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 Fe(3+ )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 Am(2 )kg(-1), indicating that the double-exchange interaction occurs between Fe3+ and Fe4+ ions.