1. Long- and Short-Range Structure of Ferrimagnetic Iron–Chromium Maghemites
- Author
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M. E. Fuentes-Montero, Emilio Morán, Marco L. Garcia-Guaderrama, Miguel Á. Alario-Franco, María E. Montero-Cabrera, Edgar Macías-Ríos, Hilda E. Esparza-Ponce, and Luis E. Fuentes-Cobas
- Subjects
Extended X-ray absorption fine structure ,Chemistry ,Maghemite ,chemistry.chemical_element ,engineering.material ,X-ray absorption fine structure ,Inorganic Chemistry ,Crystallography ,Chromium ,Octahedron ,Ferrimagnetism ,Atom ,engineering ,Physical and Theoretical Chemistry ,Absorption (chemistry) - Abstract
Maghemite-like materials containing Fe(3+) and Cr(3+) in comparable amounts have been prepared by solution-combustion synthesis. The conditions of synthesis and the magnetic properties are described. These materials are ferrimagnetic and are much more stable than pure iron maghemite since their maghemite-hematite transformation takes place at about ∼ 700 °C instead of ∼ 300 °C, as usually reported. These materials were studied by synchrotron radiation X-ray diffraction (XRD) and by X-ray absorption fine structure (XAFS) of the K-absorption edge of two elements. High-resolution XRD patterns were processed by means of the Rietveld method. Thus, maghemites were studied by XAFS in both Fe and Cr K-edges to clarify the short-range structure of the investigated systems. Pre-edge decomposition and theoretical modeling of X-ray absorption near edge structure transitions were performed. The extended X-ray absorption fine structure (EXAFS) spectra were fitted considering the facts that the central atom of Fe is able to occupy octahedral and tetrahedral sites, each with a weight adjustment, while Cr occupies only octahedral sites. Interatomic distances were determined for x = 1, by fitting simultaneously both Fe and Cr K-edges average EXAFS spectra. The results showed that the cation vacancies tend to follow a regular pattern within the structure of the iron-chromium maghemite (FeCrO3).
- Published
- 2015
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