Tailoring structural, optical and magnetic properties of spinel type cobalt oxide (Co3O4) by manganese doping

To study the effects of manganese doping on structural, optical and magnetic properties of spinel type cobalt oxide (Co3O4) system, manganese ions were doped at different concentrations (5–20%) using co-precipitation method. Crystalline nature and phase purity of the prepared materials were investigated using XRD, FTIR and XPS measurements. Manganese ions played a major role in reducing crystallite size and introducing macro/micro-strains in the doped compounds. Surface morphology of the materials examined using FESEM images confirmed the role played by manganese ion in restraining particle growth. Manganese doping was further confirmed using EDS and XPS elemental analysis. From the XPS studies, manganese concentration in the doped samples were identified to be close to the initial doping percentage (MnxCo3−xO4; x=4.61%, 8.25%, 14.13% and 18.10%). Presence of three types of manganese ions was revealed from the XPS study. Pair of absorption bands centered at 440 nm and 720 nm characteristic of spinel type cobalt oxide was observed for all the prepared materials. Micro- and macro-strains induced by manganese doping have created localized density of states reducing band energy gaps in the doped materials. Mn2+ ions replacing Co2+ ions in the tetrahedral site have enhanced the weak ferromagnetism observed for pristine cobalt oxide. Saturation magnetization, coercivity and remanent magnetization was found to increase with Mn2+ concentration.