Effect of Zn2+–Cr3+ substitution on structural, morphological, magnetic and electrical properties of NiFe2O4 ferrite nanoparticles

The Zn 2+ –Cr 3+ substituted nickel ferrite nanoparticles with a chemical formula Ni 1−x Zn x Fe 2−x Cr x O 4 (0.0 ≤ x ≤ 1.0) were successfully synthesized by a sol–gel auto-combustion method. X-ray diffraction (XRD) patterns of all the samples confirm the single phase cubic spinel structure with Fd-3m space group. In the present system, the lattice constant was increased from 8.337 to 8.396 Å with increasing Zn 2+ –Cr 3+ concentration. The average crystallite size (t) determined using the Debye–Scherrer’s formula, which lies in the range of 19–28 nm. The surface morphology was examined with field emission scanning electron microscopy (FE-SEM) and it showed that the particle size of the samples lies in the nano regime with a moderate agglomeration. The compositional stoichiometry was confirmed by energy dispersive spectrum (EDS). FT-IR spectra indicates two fundamental absorption bands, the higher frequency band ϑ 1 at 574–594 cm −1 and the lower frequency band ϑ 2 at 468–486 cm −1 arising from tetrahedral (A) and octahedral [B] sites it confirm the spinel structure. The magnetic properties of all the samples were measured using a Vibrating sample magnetometer (VSM) at room temperature. The saturation magnetization (M s ) was found to decrease due to B–B exchange and A–B superexchange interaction while remanent magnetization (M r ) and coercivity (H c ) decreases with increasing Zn 2+ –Cr 3+ concentration. The DC electrical resistivity as a function of temperature revealed the semiconducting nature of all the samples. The activation energy (E a ) was found to increase from 0.371 to 0.478 eV with an increase in Zn 2+ –Cr 3+ concentration. Overall, the Zn 2+ and Cr 3+ ions are successfully incorporated in the nickel ferrite by sol–gel auto-combustion method, and the spinel structure was not disturbed by the substitution. The magnetic and electrical properties of nickel ferrites are strongly influenced by the substitution, which may useful in technological and industrial applications.