Cation distribution and magnetic properties of CoxMg1−xFe2O4 nanoparticles

In this work, CoxMg1−xFe2O4 (x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles were prepared by hydrothermal method. Basic characterization tools were used together with the synchrotron based technique to obtain correlation between structures and magnetic properties. The XRD and SEM results confirmed the spinel structure of all prepared samples with particle sizes between 61 and 145 nm and size distribution of less than 10%. The cation valency and distribution were determined from the XAFS spectra measured at the Co and Fe K-edges. It has been shown from the result that Fe and Co ions in CoxMg1−xFe2O4 are predominantly trivalent and divalent, respectively, with no change as a function of compositions. The saturation magnetization of the x = 1 composition is much higher than those of other compositions. It was shown from the XAFS result that the added Co content in the mixture compositions could not increase the saturation magnetization substantially as the population of divalent ions in A sites are mostly Mg ions.