Effect of ytterbium on the structural, optical, magnetic and temperature dependent dielectric properties of nickel ferrite nanoparticles

In this work, nanocrystalline NiFe_2−xYb_xO₄ (x = 0.0, 0.02, 0.05, and 0.07) samples were prepared through the sol–gel auto-combustion route. X-ray diffraction (XRD) patterns confirm cubic spinel crystal structure with space group Fd-3m of all the prepared samples. Moreover, an extra phase of YbFeO₃ can be observed for values of x exceeding 0.02 in NiFe_2-xYb_xO₄ samples. The Rietveld refinement study evaluated the lattice parameters, bond lengths, and bond angle. Raman spectra also confirmed the formation of cubic spinel crystals and different vibration modes for NiFe₂O₄. FTIR spectroscopy was utilized to determine the position of various functional groups in the samples. The morphology and elemental composition were explored by using SEM and EDS analysis. The optical direct band gap is increased from 1.55 to 1.66 eV as the Yb doping concentration increases in the prepared samples. The magnetic parameters are obtained at room temperature using a vibrating sample magnetometer (VSM). The magnetic parameter (M_s and M_r) decreases with increased Yb content. The coercive field H_c and magneto-crystalline anisotropy (K) increase, thus making these types of samples best for data storage and magnetic resonance imaging applications etc. Dielectric studies showed that as the temperature increases from 100 K to 400 K, the dielectric constant increases in all the prepared samples.