Effect of lattice strain on structural, magnetic and dielectric properties of sol–gel synthesized nanocrystalline Ce³⁺ substituted nickel ferrite

The rare earth ion cerium (Ce³⁺) doped nickel ferrite nanoparticles with a structural formula NiCe_xFe_2−xO₄ (0.0 ≤ x ≤ 0.1) were procured using the sol–gel technique. The structural and morphological analysis of the as prepared sample was done using the X-ray diffraction (XRD) and HRSEM studies. A more in-depth morphological study was facilitated using the TEM, HR-TEM and SAED analysis. The position of the various ions was studied using the FTIR spectroscopy. The magnetic response of the cerium doped parent sample was recorded at room temperature using the vibrating sample magnetometer. The dielectric response of the synthesized sample was observed and analyzed at different temperatures for various frequencies. The well resolved broad peaks in the XRD pattern clearly indicated the nanosized, single phased, cubic spinel nature of these samples. There was a substantial decrease in the crystallite size on doping with cerium. Cerium was successfully substituted into the spinel lattice without any distortion. The TEM investigation revealed random shaped, sharp edged nanoparticles with a normally facetted morphology. The presence of distinctive diffractions spots on the SAED pattern indicated the formation of nanoparticles that are highly crystalline in nature. The FTIR analysis revealed a slight shift in the octahedral absorption band at γ₂ towards the lower frequency side with the incorporation of cerium ions. The magnetic properties have been seen to be altered by the addition of Ce³⁺ in the Ni ferrite matrix. The decrease in the saturation magnetization with the increase in Ce³⁺ content rendered the synthesized sample applicable in field of antenna construction. This change will be also suitable for reducing the size of the antenna. The variation of the dielectric constant with frequency indicated a monotonous decrease with increasing frequency which is a typical dielectric response of ferrites.