from the conferences organized by TANGER Ltd.
The study focuses on a comprehensive analysis of the structure and thermal stability of the magnetic parameters of two commercial ring-shaped strontium ferrite magnets, for which the manufacturing conditions were unknown. Structural characterization was carried out using powder Xray diffraction (XRD) and scanning electron microscopy (SEM) with EDX analysis. XRD confirmed the magnetoplumbite-type structure SrFe12O19 in both samples. Evaluation of the March parameter revealed a pronounced preferential grain orientation in the (001) plane for the anisotropic sample, while the isotropic sample exhibited no significant texture.Magnetic properties were determined from the J-H and B-H magnetization curves measured using the hystergraph in the temperature range of 25-190 °C. Anisotropic sample exhibited a rectangular magnetization curve with a remanence-to-saturation ratio of 0.951-0.923, which decreased only by a few hundredths with increasing temperature. In the isotropic sample, this ratio was lower (0.663–0.649), and the corresponding curves displayed a significantly more rounded shape. With increasing temperature, both samples showed a linear decrease in remanent induction, saturation polarization, and the maximum energy product BHmax (Pearson correlation coefficient ≈ 0.99). The slope of the remanent induction decrease was −1.178 mT·K-1 for anisotropic and approximately −0.423 mT·K-1 for isotropic sample. A similar trend was observed for saturation polarization and BHmax. In contrast, the coercive field HcJ increased linearly, with slopes of 0.908 kA·m-1·K-1 for anisotropic and 0.735 kA·m-1·K-1 for isotropic sample. The Curie temperature of both samples was determined to be approximately 450 °C. The results confirm higher remanent induction and energy product values for the anisotropic ferrite; however, these are accompanied by a more pronounced temperature dependence of the magnetic parameters.
Keywords: Ferrites, hystergraph, crystal structure, magnetization curve, March parameter© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.