Structural, Magnetic, and Dielectric Properties of Ni0.5Zn0.5Al x Fe2−x O4 Nanoferrites

This work investigates the effect of non-magnetic aluminum (Al) substitution in structural, morphological, magnetic, and dielectric properties of nanosized Ni0.5Zn0.5Al x Fe2−x O4 (0.0 ≤ x ≤ 0.25) synthesized through citrate-gel autocombustion route (CGAC). Structural characterizations were performed by using X-ray powder diffraction (XRD), FT-IR, and scanning electron microscope (SEM). XRD reveals the formation of single-phase cubic spinel with crystallite sizes around 62–57 nm for all Al substituted samples estimated from Williamson-Hall method. Two significant absorption bands around 600 cm−1 and 400 cm−1 are observed from FT-IR spectra of samples under investigation, which confirms the formation of a single-phase cubic spinel. Interionic bond lengths and bond angles confirm the solubility of Al in the spinel lattice and support the observed variation in magnetic properties. Using vibrating sample magnetometer (VSM) saturation magnetization, coercivity has been measured. A decrease in lattice parameter, saturation magnetization with increasing Al concentration was attributed to the difference in the ionic radii and weakening of exchange interactions. The decrease in initial permeability explained on the basis of variation in grain size and porosity. Dielectric constant and dielectric loss decreases with increasing Al concentration and with frequency.