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Zn and Co incorporated with Fe2O4 show different magnetic behaviors, the former can be adjusted between ferromagnetic and antiferromagnetic while the later one displays ferromagnetic ordering. This work presents a mixed system of Co–Zn with Fe2O4 for its potential applications in optical communication, data storage, and magneto-optical devices. ZnxCo1-xFe2O4 (x = 0.00, 0.25, 0.50, 0.75, 1.00) nanostructures were prepared through Sol–Gel method followed by annealing at 800 °C. XRD results showed the cubic nature of all samples with grain sizes of 14–21 nm having high values of specific surface area (71–81 m2 g−1). A linear increase in lattice constant from 8.3934 to 8.4322 Å is reported with the increase in Zn+2 concentration from 0 to 1, i.e., following Vegard's law. Magnetic properties for x = 0.5 sample studied up to 5 K, and an improvement has been reported, e.g., Ms from 40 to 88 emu.g−1, Hc up to 2236 Oe, nB from 1.72 to 3.75 μB,Hex up to 32.44 Oe, and αY-K ranged from 50° to 16°. Switching is reported in direct B.G for x = 0.25, x = 0.50, and in indirect B.G for x = 0.75. Prepared nanostructures have long ranged nonlinear refractive index (0.48–5.34) and metallization criterion from 0.37 to 0.45. Increased Zn+2 content in CoFe2O4 resulted a decrease in Urbach energy from 318 to 141 meV. High values of lattice dielectric constant, direct B.G and large values of activation energies, optical and electrical conductivities suggested that prepared samples (especially with x = 0.50) have potential for use in efficient electronic devices such as sensors, photoconductors, solar cells and high-capacity energy storage devices such as supercapacitors. Dielectric and optoelectronic properties for ZnxCo1-xFe2O4 surpassed all the previous work. [ABSTRACT FROM AUTHOR]

Nanocrystalline Mn-Zn ferrite nanopowders (Mn0.5Zn0.5Fe2O4) were synthesized by co-precipitation technique and post-fabrication annealing has been performed at different temperature ranges from 400 to 700 °C for 2 h. The effect of annealing on morphology, crystalline phase formation, cation distribution, lattice constant, particle size, magnetic properties, and optical properties was studied by scanning electron microscopy (SEM), x-ray diffraction (XRD), vibrating sample magnetometer (VSM), and UV-visible spectroscopy (UV-Vis) respectively. The crystallite size increased from 14 to 24 nm with the annealing temperature owing to the grain growth process or more technically we say Ostwald ripening mechanism. The decomposition of ferrites at low-temperature results in the formation of hematite Fe2O3 eventually reduced the magnetic properties of ferrites. The hematite, impurity phase, started to dissolve or converted into the ferrite phase after 600 °C. The sample annealed at 700 °C shows a better crystalline structure, phase formation, and larger magnetization compared to the other ferrite samples. The improved magnetic behavior after heat treatment is due to the better alignment of domains at the cost of the grain growth process. The UV-Vis spectroscopy result revealed the maximum absorbance at 380 nm. [ABSTRACT FROM AUTHOR]