Thermal analysis and Magnetic characterization of M-type SrFe12O19 nanodisks

Abstract

In the present work, the thermodynamic analysis and magnetic properties as a function of temperature were investigated using calorimetric and VSM measurements of SrFe₁₂O₁₉​ nanodisks, which were obtained by a sonochemical-assisted method. The XRD analysis confirms the successful synthesis of single-phase SrFe₁₂​O₁₉​ powder (98 wt.%) at 2.4 W/cm³, with a disk-shaped morphology revealed by SEM analysis. The TGA/DSC measurements show five stages of mass loss in the range of 273–1073 K, which are identified as an oxidation process. The activation energy ($E_a$) was determined using mass loss identifications from the thermogram and the Coats-Redfern model. This model provides overall kinetic data, such as the Gibbs free energy ($\Delta$G), enthalpy ($\Delta$H), and entropy ($\Delta$S). In all cases, values of the $\Delta$S were negative, demonstrating that the composite has a more organized structure compared to the starting material. The SrFe₁₂O₁₉​ single-phase material showed superparamagnetic behavior with a coercivity field of 0.56 kOe at 100 K and a saturation magnetization of 71.05 emu/g, which was determined using the Law of Approach to Saturation method.