Aluminium doped Ni-Zn ferrite nanoparticles of general formula of Ni0.5Zn0.5AlxFe2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0) have been synthesized by sol-gel auto combustion method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform spectroscopy (FTIR) and vibrating sample magneto meter (VSM). XRD studies confirm that all compositions show single phase cubic spinel structure. The crystallite size was calculated using the Debye-Scherrer formula and found in the range of 17 -52 nm. The lattice parameter "a" is found to decrease with increasing Al 3+ content. The SEM images clearly show the crystalline structure and EDX patterns confirm the compositional formation of the synthesized compositions. The results of FTIR analysis indicated that the functional groups of Ni-Zn spinel ferrite were formed during the sol-gel synthesis process. The IR spectra showed two main absorption bands, the high frequency band ν1 around 600 cm −1 and the low frequency band ν2 around 400 cm −1 arising from tetrahedral (A) and octahedral (B) interstitial sites in the spinel lattice. As doping is increased the magnetic behavior is found to decrease and the composition x = 2.0 ferrite appears to be exhibiting superparamagnetism as the coercive field and retentivity are found near zero.

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Ni-Zn-Al nanoferrites of general formula Ni x Zn 1-x Al Fe O 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by sol-gel auto combustion technique. The X-ray diffraction and FTIR studies confirmed the formation of single cubic spinel structure. Dielectric performance and AC conductivity of prepared mixed nanoferrites were carried out using LCR impedance meter. It was observed that both dielectric constant and dielectric loss were decreased by increasing the frequency whereas AC conductivity increases with applied frequency but decreases with increasing the Ni 2+ ion substitution for a fixed Al 3+ ion concentration. DC resistivity, activation energy and Curie temperature were calculated by using the two probe experimental method. It was observed that DC resistivity decreased whereas the charge mobility increased with increasing the temperature. DC resistivity and activation energy of the nanoferrite samples were increased with Ni 2+ ion substitution for a fixed Al 3+ ion concentration.

Ni-Zn-Al mixed ferrite nanoparticles, with general formula Ni x Zn 1-x AlFeO 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), were synthesized by sol-gel auto combustion technique. All prepared ferrite nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometer. X-ray diffraction study confirmed the formation of the single phase cubic spinel structure in all ferrite samples. The crystallite size was calculated by the Debye-Scherrer formula and found to be in the range 15-46 nm. The lattice constant decreased with increasing Ni 2+ ion concentration. Scanning electron microscopy images clearly indicate that the particles are very small but agglomerated. Energy dispersive X-ray was used to confirm the composition of the prepared powders. Fourier transform infrared spectra showed two main absorption bands of ferrite nanoparticles, the high frequency band (ν 1) around 600 cm-1 and the low frequency band (ν 2) around 400 cm-1 arising from tetrahedral (A) and octahedral (B) interstitial sites in the spinel lattice, respectively. Vibrating sample magnetometer results reported that the saturation magnetization, remanent magnetization and magnetic moments decrease with increasing Ni 2+ ion concentration.

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