Tunable structural, morphological, and hysteresis characteristics of SrFe₁₂O₁₉/Fe₃O₄ composites

In this communication, Lanthanum (La) and Cobalt (Co)-substituted hard Strontium ferrite (SrCo_1.5zLa_0.5zFe_12−2zO₁₉) (80%) and soft magnetite (Fe₃O₄) (20%) composites by weight with different levels of substitution from z = 0.0 to 0.5 were successfully synthesized. The X-ray diffraction analysis of doped composites revealed the co-existence of hard (M-type) and soft (spinel) ferrite phases without any impurity peak and z = 0.0 exhibited minor traces of α-Fe₂O₃. Fourier infrared spectroscopy (FTIR) analysis revealed the existence of three precise absorption bands in the range of 400–800 cm⁻¹ attributing primarily to iron oxide. Field emission scanning electron microscopy exhibited hexagonal platelet-shaped particles along with randomly oriented and small cubical-shaped grains. Both saturation magnetization and remanent magnetization increased from z = 0.0 to z = 0.1, while further substitution to z = 0.5 caused a gradual decrease in both parameters. The VSM measurement exhibited an increment in H_c from z = 0.0 (607.79 Oe) to z = 0.2 (3084.73 Oe), and it decreases to z = 0.5 (1589.40 Oe) with further substitution of Co–La ions. Switching field distribution plots (dM/dH against H) indicated the strong exchange coupling effect between hard/soft phases for z = 0.0 and insertion of Co–La ions causes abatement in this coupling.