A sol-gel auto combustion approach was used to synthesize Co2+ substituted M-type strontium hexagonal ferrite with the chemical formula Sr1-xCoxFe12O19 (x=0.0, 0.25, 0.50 and 0.75). X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Raman Spectroscopy and Vibrating Sample Magnetometer (VSM) have been used to investigate the structural and magnetic properties as a function of cobalt ions substitution in Sr-hexaferrite. XRD pattern disclosed a single M-type hexagonal crystalline phase at x=0, while a desired phase of the strontium M-type hexaferrite with undesired phase appeared with the increase of the cobalt contents. FE-SEM images showed that the particles have irregular distribution and non-uniform shape. Generally, the cobalt ions substitution does not alter the surface morphology. The Raman spectra measurement proved the formation of magnetoplumbite structure of Sr1-xCoxFe12O19 system. The pure strontium hexaferrite compound showed sharp and intense peaks. The intensity of the peaks decreased when the Co2+ ions contents increased. VSM measurements showed ferromagnetic properties for all synthesized samples. The magnetic properties such as saturation magnetization (M-s), remanence magnetization (M-r), coercive field (H-c), effective anisotropy constant (K-eff), anisotropy field (Ha), and squareness ratio (S) showed a progressive decrease with the increase of the cobalt ions substitution in the M-type strontium hexaferrite system. Replacement of strontium (Sr) by cobalt (Co) ions weakens the super-exchange interactions among particles.
