Impact of Mn-substitution on structural, optical, and magnetic properties evolution of sodium–cobalt ferrite for opto-magnetic applications

Mixed-metal oxide spinel ferrite nanoparticles of composition Na 0.5 Mn x Co (0.5− x ) Fe 2 O 4 (where x = 0.0, 0.1, 0.3, and 0.5) were synthesized successfully through a well-known citrate sol–gel autocombustion method. X-ray diffraction approach, transmission electron microscope, scanning electron microscope, and spectroscopic Fourier transform infrared were used to investigate the microstructure and the formation of the composites. Diffuse reflectance was employed to investigate the optical properties and estimating of optical band gap type and value. The magnetic analysis was made by employing a vibrating sample magnetometer. It was found that the average crystallite size increases with the increase of manganese (Mn) content. The formation of the spinel structure of Mn-doped Na-CFO was confirmed by FTIR spectra. The direct optical band gap was observed through the Kubelka–Munk function calculation of diffusely reflected light. The saturation magnetization decreases with the addition of Mn cations.