Synthesis and characterization of nano-crystalline Zn-substituted Mg–Ni–Fe–Cr ferrites via surfactant-assisted route

Nano-crystalline ferrites of Mg0.8−xZnxNi0.2FeCrO4 with stoichiometric proportion (x) lying between 0.0 and 0.8 were synthesized by sol–gel template using cationic, anionic and nonionic surfactants. The resultant powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and vibrating scanning magnetometry (VSM). XRD indicated the formation of polycrystalline single-phase cubic spinels with average crystallite sizes in the range of 10–15 nm. The structural data, as a function with Zn-content, has been explained on the basis of the entire cation distribution. Magnetic hysteresis loops showed very narrow hysteresis curves, which infer that the prepared powders are superparamagnetic. The smaller magnetization values obtained for all the samples can be attributed to larger surface-to-volume ratio and the spin canting on their surface. The effect of surfactant type, Zn-substitution and the presence of Cr3+ ions on the structural and magnetic properties of the investigated system was estimated and discussed.