Investigation of Stability and Magnetic Properties of Ni- and Co-Doped Iron Oxide Nano-particles

The current work is dedicated to investigate the effect of nickel and cobalt doping on the crystallanity, stability, and magnetic and optical properties of magnetite (Fe3O4) nano-particles. Nickel-and cobalt-doped magnetite (NixFe(3)-xO4 and CoxFe(3)-xO(4) with x = 0, 0.05, 0.1, and 0.15) nano-particles have been prepared by chemical co-precipitation method and are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), themogravimetric analysis (DSC-TGA), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and UV-visible spectroscopy to study their structural, thermal, morphological, magnetic, and optical properties, respectively. The structural analysis indicates the formation of a single-phase cubic inverse spinel structure with a decrease in lattice parameters with increasing Ni and Co concentrations. Thermal analysis reveals that the transition temperature increases. The increase in transition temperature is due to the maghemite to hematite phase transition after the replacement of Fe2+ with Co2+ or Ni2+ in the B-site. The increase in transition temperature is attributed to the fact that stability increases with increasing cobalt content. Morphological analysis indicates the spherical shape of nano-particles with least agglomeration at all concentrations. The optical band gap energy increases as the particle size decreases. Magnetic properties reveal that the saturation magnetization decreases in both cases, but coercivity increases in the case of Co. This behavior is ascribed due to the high anisotropic cobalt cation doping in magnetite (Fe3O4) nano-particles, which is the goal to achieve the increase in hyperthermic efficiency.