Crystal and magnetic structures in perovskite-related La1-xCaxFeO3-δ (x=0.2, 0.33)
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Date
2011-12
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Elsevier
Abstract
Using sol gel synthesis, single phase perovskite-related compounds in the family La1-xCaxFeO3-δ have been formed for x=0.2 and x=0.33, but not for x=0.5. The x=0.2 and x=0.33 compounds are isostructural with LaFeO3 (Pnma). The magnetic structure of La 0.8 Ca0.2FeO3-δ has been studied through Mössbauer spectroscopy and neutron powder diffraction. La 0.8 Ca 0.2FeO3-δ is a G-type antiferromagnet with a magnetic moment magnitude of 3.0±0.2μB at room temperature. The reduction in the magnitude of the antiferromagnetic moment compared to that published for LaFeO3 is explained by the measurement being taken at room temperature rather than 4 K and by the presence of Fe4 ions which have weaker exchange interactions than Fe3, causing a strong reduction in TN. Room temperature Mössbauer shows a broad magnetic hyperfine field distribution on the Fe sites in both La0.8 Ca0.2FeO3-δ and La0.67 Ca 0.33FeO3-δ. On cooling, disproportionation of Fe14 into Fe3 and Fe5 is apparent, and the resulting Fe5 sextet measured at low temperature gives a reliable measure of the Fe4 fraction. This in turn shows that creation of high-oxidation-state Fe is the dominant charge balance mechanism on doping Ca2 into the Ln3 site indicating a disordered distribution of Fe3 and Fe4. The lack of broadening of the Fe 5 sextet suggests that there may be ordering in the distribution of Fe5. © 2011 Elsevier Ltd.
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Keywords
Crystallography, Magnetism, Perovskite, Spectroscopy, Antiferromagnetic materials, Calcium, Iron oxides, Lanthanum compounds
Citation
Hudspeth, J. M., Stewart, G. A., Studer, A. J., & Goossens, D. J. (2011). Crystal and magnetic structures in perovskite-related La1− xCaxFeO3− δ (x= 0.2, 0.33). Journal of Physics and Chemistry of Solids, 72(12), 1543-1547. doi:10.1016/j.jpcs.2011.09.014