Structural, Optical, and Magnetic Characteristics of (Zn_0.5Ni_0.5Fe₂O₄)_0.5(Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉)_0.5 Nanocomposite Synthesized by the Ball-Milling Assisted Co-precipitation Route

In this study, the structural, optical, and magnetic properties of the Zn_0.5Ni_0.5Fe₂O₄ soft ferrite nanoparticle, the Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉ hard ferrite nanoparticle, and their nanocomposite (Zn_0.5Ni_0.5Fe₂O₄)_0.5(Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉)_0.5 have been investigated. The nanoparticles and the nanocomposite were synthesized via co-precipitation and ball-milling routes, respectively. The formation, purity, and crystallinity of the samples were verified from the Rietveld analysis of X-ray diffraction (XRD) data as well as the essential absorption bands in the Fourier transform infrared (FTIR). The morphology and lattice spacing were investigated using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED). TEM micrographs visualized the hexagonal morphology of Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉ phase and the spherical-like shape of Zn_0.5Ni_0.5Fe₂O₄ phase. A scanning electron microscope (SEM) revealed well-distributed grains in the composite. Furthermore, energy-dispersive X-ray analysis (EDX) analysis validated the chemical compositions and the coexistence of Zn_0.5Ni_0.5Fe₂O₄ and Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉ phases in one matrix. Additionally, the optical behavior of the samples was tested via ultraviolet–visible and photoluminescence spectroscopies. Tauc plots were used to estimate the direct energy gap using UV spectroscopy. The direct and indirect energy band gaps of (Zn_0.5Ni_0.5Fe₂O₄)_0.5(Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉)_0.5 nanocomposite are in between that of the pure phases, due to the increase in energy states with particle size. Also, near-band edge emissions and deep-level emissions have been observed in PL studies. X-ray photoelectric spectroscopy (XPS) studies were performed to investigate the elemental composition and cationic distribution. A good exchange coupling between both nanoparticles was verified via a single-phase behavior in the magnetic hysteresis loop. (Zn_0.5Ni_0.5Fe₂O₄)_0.5(Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉)_0.5 nanocomposite had a higher saturation magnetization ( \({M}_{s}\) $M_s$ ) compared to Ba_0.4Sr_0.4Ca_0.2Fe₁₂O₁₉ phase and a squareness ratio (SQR) of 0.207 value ( \(<0.5),\) $<0.5),$ making it suitable for use in magnetic hyperthermia, the production of permanent magnets, and extremely sensitive for magnetic recording media.