Electronic structure studies of nanoferrite Cu _xCo _1-xFe ₂O ₄ by X-ray absorption spectroscopy

Pure and mixed cobalt copper ferrites are of great interest due to their widespread application in electronics and medicine. We report on the electronic structure of a nanoferrite Cu _xCo _1-xFe ₂O ₄ (0.0≤x ≤1.0) system studied by X-ray absorption spectroscopy. These magnetic nanoferrites (average crystallite size ∼31-43 nm) were synthesized by an auto combustion method and are characterized by high resolution X-ray diffraction and near edge X-ray absorption fine structure measurements at the O K and Co, Cu, and Fe L-edges. The O K-edge spectra suggest that there is a strong hybridization between O 2p and 3d electrons of Co, Cu and Fe cations and Fe L _3.2-edge spectra indicate that Fe ions coexist in mixed valence states (Fe ³⁺ and Fe ²⁺) at tetrahedral and octahedral sites of the spinel structure. Copper and cobalt ions are distributed in the divalent state in octahedral sites of the spinel structure. The origin of high saturation magnetization and coercivity in cobalt-copper ferrites are explained in light of these results. Copyright