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Cation distribution and magnetic properties of natural chromites
Author(s) -
Rais A.,
Yousif A. A.,
Alshihi M. H.,
Alrawas A. D.,
Gismelseed A. M.,
Elzain M. E.
Publication year - 2003
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200301816
Subject(s) - spinel , octahedron , materials science , analytical chemistry (journal) , paramagnetism , mössbauer spectroscopy , crystallography , magnetic moment , mineralogy , chemistry , condensed matter physics , crystal structure , physics , metallurgy , chromatography
Ten specimens of chromites from Oman ophiolites have been studied using magnetic susceptibility χ measurements, Mössbauer spectroscopy (MS), Scanning electron microscopy (SEM), and X‐ray diffraction (XRD). XRD shows that all samples have a face‐centered cubic spinel structure. MS analysis and SEM data at room temperature enabled to derive the chemical formula and the cations distribution among tetrahedral (A1 and A2) and octahedral (B) sites. For all specimens, paramagnetic variations of 1/ χ with the temperature T show a systematic curve bending at a critical temperature T 0 , which indicates a change of the effective paramagnetic moment μ eff . This deviation from Curie–Weiss law is interpreted as due to spin inversion of a fraction δ of Cr 3+ cations located in the octahedral sites of the spinel structure. This interpretation is supported by a decrease in the Mössbauer peak areas of Fe 2+ located in A1 sites from 300 to 80 K at the expense of Fe 2+ located in A2 sites. The values of δ and μ eff for each specimen are calculated by fitting this model separately to the experimental 1/ χ versus T above and below T 0 .