Structural, dielectric and magnetic properties of terbium doped strontium spinel ferrite (SrFe₂O₄) synthesized by sol-gel method

In this research work, sol-gel technique was employed to prepare the strontium based spinel ferrite nanoparticles (SrFe₂O₄) with different ratios of terbium (Tb). Different characterization techniques were used to investigate the structural, morphological, dielectric and magnetic properties of the prepared samples. X-ray diffraction (XRD) result suggests that face-centered cube spinel nanocrystalline structure is formed. Crystallite size of the SrFe₂O₄ decreases with rising of Tb ratio. The morphology, shape and size of the SrFe₂O₄ were examined by scanning electron microscopy (SEM) analysis and results reveal inhomogeneous distributions of the nanostructures with high agglomeration. The electrical resistivity of the SrFe₂O₄ increases with rising of Tb ratio, which is confirmed from the cyclic voltammetry. It is observed that dielectric constant of all the samples decreases with the increasing frequency range. It is determined that the dielectric constants of the spinel ferrites are frequency dependent and decrease with increasing the frequency of applied electric field. The magnetic behavior of SrFe₂O₄ with different ratios of Tb was studied and it is found that the saturation magnetization values of samples decrease with increase in the substitution of Tb³⁺ at octahedral sites for Fe³⁺. This decrease in the values of M_s is also attributed to spin at surface of nanoparticles.