Temperature-dependent dielectric and magnetic properties of NiFe2O4 nanoparticles

This work described the structural, morphological, temperature-dependent relative permittivity, and magnetic behavior of nickel ferrite (NiFe2O4) nanoparticles prepared via a facile co-precipitation method. A computational analysis, density functional theory (DFT) calculation was carried out to understand the band structure and density of the state of NiFe2O4. The crystallinity and phase purity was analyzed by powder X-ray diffraction, which confirms the polycrystalline nature of the cubic spinel structure of NiFe2O4 belonging to the Fd3m space group. The calculated crystallite size is about 22 nm. Field emission scanning electron micrograph confirms the agglomerated flake-like grains. All the phonon modes (A(1g), E-g and T-2g) confirm the inverse spinel cubic structure of NiFe2O4. The dielectric study shows that the relative permittivity is varied between 1.2 x 10(2) and 1.6 x 10(3) as a function of different temperature. The obtained semicircle arc from the Cole-Cole plot confirms the grain and grain boundaries contribution in the conduction process. The exploration of the magnetic hysteresis loop measured in the temperature between 5 and 300 K over the field strength of +/- 2 T, revealed a ferromagnetic behavior. Temperature-dependent magnetization and coercivity were studied using modified Bloch's law and Kneller's law, respectively. The increasing magnetic parameters at low temperature may be due to increasing the surface-spin moment in the finite-size nanoparticles.