Development and characterization of superparamagnetic Zn-Doped Nickel ferrite nanoparticles

The nanocrystalline Zn-doped Nickel ferrite nanoparticles, Zn_xNi_1-xFe₂O₄ (x = 0.2, 0.4, 0.6 and 0.8) have been developed using the sol–gel method. The average crystallite size was calculated using the Debye- Scherrer formula through X-ray diffractometry and found to be in the range of ∼ 4 nm to 7 nm. Rietveld refinement of the prepared samples suggested the cubic spinel phase of the nanoparticles. For the surface morphology analysis of the nanoparticles, the Field Emission Scanning Electron Microscope (FESEM) technique was utilized, which showed the spherical shape of the particles. Elemental Dispersive X-ray spectroscopy (EDAX) ascertained the experimentally obtained elemental composition with the calculated elemental composition and identified the elements present within the sample. Fourier Transform Infrared Spectroscopy (FTIR) revealed the two prominent absorbing bands, i.e., tetrahedral complex, υ¹ and octahedral complex, υ² in the range of 4000–300 cm⁻¹. Photoluminescence spectroscopy and UV Visible diffuse reflectance spectroscopy determined the optical properties of the samples and it was observed that with the increasing concentration of Zinc, the value of band gap decreased from 2.29 eV to 2.11 eV. The M−H curves of the Zn-doped nickel ferrites exhibit superparamagnetic behavior at room temperature, confirming the presence of a single domain in the sample.