Room Temperature Magnetism and Experimental Electron Density Analysis of Co2+ Doped ZnFe2O4 Spinel Nanoferrites

A clear understanding of the microstructural and physical properties of materials is an essential requirement for the advancement of industrial device applications. In this context, single-phase spinel Co2+ -doped ZnFe2O4 (CoxZn1-xFe2O4: x = 0.05, 0.10, 0.15, 0.20) was synthesised by autocombustion and characterised structurally and magnetically by x-ray and vibrating-sample magnetometry (VSM), respectively. Scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) were used for surface morphology and elemental composition analysis. UV-Visible spectrophotometry was used for optical band gap analysis. Rietveld refinement study yielded the refined structure factor for each Bragg plane, cell constant and oxygen positional parameter. Both cation distribution analysis and VSM studies revealed a cubic spinel structure with a partial distribution of Fe3+ ions at the tetrahedral A and octahedral B sites and the complete incorporation of Co2+ and Zn2+ ions at the octahedral B site. The bonding strength and electron density distribution between tetrahedral A and octahedral B sites via oxygen ions were analysed using the maximum entropy method (MEM). A precise 3D and 2D visualisation of the tetrahedral A and octahedral B sites gives the electronic isosurface shape, size, and bonding behaviour for all the compositions. Maximum A-O covalent bonding and maximum B-O ionic bonding favours an increase in coercivity. The magnetic hysteresis analysis (VSM) reveals a slow switching from paramagnetic to superparamagnetic behaviour with increased Co2+ content. The maximum magnetisation and coercivity in this present work are double the value compared to the reported values.