Annealing temperature dependence of crystalline structure and magnetic properties in nano-powder strontium-substituted cobalt ferrite

Strontium-substituted cobalt ferrite nanoparticles were synthesised via the co-precipitation method. Thermogravimetric analysis (TGA) showed that the relative reduction of the mass was supported by the available strontium cations. X-ray diffraction analyses clarified that single-phase nanoparticles were obtained and indicated that the strontium cations substituted metal cations in the cobalt ferrite nanoparticle system. The crystallite size increased on increasing the annealing temperature. By contrast, the crystalline stress decreased on increasing the annealing temperature. Furthermore, the saturated magnetisation decreased with an increased annealing temperature. Finally, the annealing temperature dependence of the coercive field is shown in this paper and the highest coercive field, H_C, of 2.76 kOe is obtained for Sr_0.1Co_0.9Fe₂O₄ nanoparticles with an annealing temperature of 1000 °C. Here, the Sr²⁺ cations facilitate the high value of the anisotropic magnetic realisation for the whole annealing temperature treatment.