Studies on Magnetic Properties and Exchange Spring Coupling Interaction Between Hard Barium Hexaferrite (BaFe ₁₂ O ₁₉ ) and Soft Nickel Ferrite (NiFe ₂ O ₄ ) Particulate Composite Thick Films

In this study, Hard:BaFe12O19 and Soft:NiFe2O4 ferrite powders were synthesized by the solid-state route and characterized for phase purity and crystallinity using XRD and morphology by FE-SEM. To investigate the effect of milling time on the magnetic properties, the composite systems have been subjected to ball milling for different durations (0, 5, and 10 h) and processed into highly flexible particulate composite thick films by tape casting with PVDF polymer matrix. The presence of kinks in MH loops and Mr/Ms values less than 0.5 in the 0, 10-h tapes indicate the magnetostatic interactions, a smooth MH loop, and Mr/Ms values slightly greater than 0.5 in the 5-h tape indicate exchange spring coupling between hard and soft phases. Furthermore, three distinct peaks were observed in the dM/dH vs H graphs (which gives a better understanding of exchange coupling) for 0- and 10-h tapes, indicating a magnetostatic interaction. Whereas, in the 5-h composite, only two broad peaks with a shoulder on either side of the Y-axis confirm the weak exchange coupling. In addition, the moderate values of magnetic anisotropy (K1=4.52x105 erg/g), anisotropic field (Ha=17569 Oe), and BHmax(= 0.365 MGOe) values confirmed the cooperative magnetization reversal in the 5 hrs tape than others.