Structural, magnetic and electrical properties of Al 3+ substituted Ni–Zn ferrite nanoparticles

Abstract

Nanocrystalline ferrite materials having the general formula Ni 0.7Zn 0.3Fe 2− x Al x O 4 (0.0 ≤ x ≤ 0.5) have been synthesized by citrate-gel auto combustion method and characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), field emission scanning electron microscopy (FE-SEM), dc magnetization, dielectric and impedance spectroscopy measurements. XRD studies confirm that all the samples show single phase cubic spinel structure. The crystallite size of Ni 0.7Zn 0.3Fe 2− x Al x O 4 (0.0 ≤ x ≤ 0.5) nanoparticles calculated using the Debye–Scherrer formula was found in the range of 13–17 nm. The value of lattice parameter ‘ a’ is found to decrease with increasing Al 3+ content. EDX patterns confirm the compositional formation of the synthesized samples. FE-SEM micrographs show that all the samples have nano-crystalline behavior and particles show spherical shape. The variation of dielectric properties ɛ′, ɛ″, and tan δ with frequency shows the dispersion behavior which is explained in the light of Maxwell–Wagner type of interfacial polarization in accordance with the Koop's phenomenological theory. The dc magnetization studies infer that magnetic moment of Ni 0.7Zn 0.3Fe 2− x Al x O 4 (0.0 ≤ x ≤ 0.5) nanoparticles was found to decrease with Al doping. Impedance spectroscopy techniques have been used to investigate the effect of grain and grain boundary on the electrical properties of the synthesized compounds.