Cation distribution and magnetic properties of natural chromites

摘要: Ten specimens of chromites from Oman ophiolites have been studied using magnetic susceptibility χ measurements, Mossbauer spectroscopy (MS), Scanning electron microscopy (SEM), and X-ray diffraction (XRD). XRD shows that all samples a face-centered cubic spinel structure. MS analysis SEM data at room temperature enabled to derive the chemical formula cations distribution among tetrahedral (A1 A2) octahedral (B) sites. For specimens, paramagnetic variations 1/χ with T show systematic curve bending critical 0 , which indicates change effective moment μ eff . This deviation Curie-Weiss law is interpreted as due spin inversion fraction δ Cr 3+ located in sites interpretation supported by decrease peak areas Fe 2+ A1 300 80K expense A2 The values for each specimen are calculated fitting this model separately experimental versus above below