Synthesis, structural characterization, and magnetic properties of mixed ternary spinel-Type Mn-Ni-Co oxides

Mixed ternary spinel-Type oxides Mn_xNi_1-xCo₂O₄ (x = 0, 0.5, 1) were synthesized using a citrate sol-gel route. The morphologies and structures of the mixed oxide nanoparticles were characterized using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Fourier-Transform Infrared Spectroscopy (FTIR). Structural analysis from XRD and FTIR confirm the formation of single phase cubic spinels. TEM and SEM images show the formation of interconnected nanoparticles. The particle sizes obtained from TEM and XRD are consistent with each other. It was observed that the lattice constant increases with increasing Mn concentration from x=0 to x=0.5 and then decreases with further increase in Mn concentration to x=1. Magnetization measurements were carried out using Vibrating Sample Magnetometery (VSM), which showed that the oxides have weak ferromagnetic behavior with the presence of an antiferromagnetic component. The oxide with the highest Mn substitution was observed to be superparamagnetic at room temperature.