Structural, magnetic and dielectric properties of nano-crystalline spinel NixCu1-xFe2O4

A series of nickel substituted copper ferrite nanocrystals (NixCu1-xFe2O4, x = 0 , 0.1 , 0.3 , 0.5 , 0.7 ) were synthesized by co-precipitation technique. The prepared powders were calcined twice at 900 °C (pre-calcination) and 1100 °C (post-calcination) respectively. The structural, morphological and magnetic properties were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transformed infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM), respectively. XRD analysis shows that all the samples have a single-phase cubic spinel structure. The crystallite size was calculated by using Debye-Scherrer’s formula. It was observed that the crystallite size decreases with the increasing nickel (Ni) content and increases after post-calcination. The saturation magnetization increased with the increasing Ni content, whereas the coercivity decreased. The saturation magnetization further increased after post-calcination. The parameters such as dielectric constant, dielectric loss and ac conductivity were also studied in the frequency range from 1 to 12 GHz. The complex dielectric permittivity of NixCu1-xFe2O4 nanocrystals was decreased with the increasing Ni contents and as well as after post calcination. Furthermore, the dielectric loss tangent and ac conductivity also decreases with the increasing Ni contents and as well as after post calcination.