The cobalt substituted Nickel-Zinc ferrites with the composition Ni0.95-xZn0.05CoxFe2O4, for x= 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 were synthesized by the soft chemical route method and were found to have cubic system of ferrimagnetic spinel using XRD. The grain sizes decreases significantly with the cobalt content (x) and are 1.62-1.36nm for x = 0.01 to 0.06 which are small enough to produce appropriate high density recording media. The particle size is found to be in the range 29-22 nm with the help of SEM. Their magnetic properties determined with VSM show the dependency on the exchange interaction due to the cobalt substitution between the metal ions of tetra and octahe.

The soft chemical method was adopted for the synthesis of cobalt substituted nickel-zinc and zinc-nickel ferrites (Ni0.95-xZn0.05CoxFe2O4 and Zn0.95-xNi0.05CoxFe2O4 for x= 0.01, 0.02, 0.03, 0.04, 0.05, and 0.06. We have recently studied the structural, morphological, magnetic properties, initial permeability, and dielectric constant of the samples. They are found with cubic ferromagnetic spinel structure along with the morphology suitable for high-density recording media. The effective initial permeability μi (μeff) is found to depend on magnetocrystalline anisotropy constant K1 and grain size D. From this present study, the dc resistivity is found to increase linearly with Co2+ substitution for both ZNCF and NZCF ferrites up to x=0.04. After that, the material changes its ferromagnetism to paramagnetism thereby increasing the activation energy. The difference between the two magnetic states (Ferro and para) in NZCF is found to be greater than in ZNCF. The phase transition helps to determine the Curie temperature. The ac conductivity takes place by the hopping of charge carriers called polarons. The conductivity is enhanced with frequency.

The Zinc Nickel Cobalt Ferrite (ZNCF) Zn0.95−xNi0.05CoxFe2O4, for x= 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 were prepared by co-precipitation. XRD patterns show spinel ferrite with a cubic structure. The lattice parameter was found to increase linearly with cobalt concentration (x). FESEM gave the grain sizes in the range 1.61-1.38nm and particle size in the range 28-21 nm for x = 0.01 to 0.06. The porosity was in the range 92.6-92.9 %. The occupancy of metal ions in the two interstitial sites affects the exchange interaction. The higher grain size and lower porosity have a positive impact on magnetic saturation which makes them applicable in recording media.

The soft chemical method was adopted to prepare of cobalt-substituted nickel-zinc ferrites (Ni0.95-x Zn0.05COx Fe2O4 for x = 0.01, 0.02 and 0.03). We have recently studied their structural, morphological, and magnetic properties, initial permeability, and dielectric constant. They were found to be with cubic ferromagnetic spinel structure, the morphology of which is suitable for high-density recording media. The impedance has a major role in characterizing the electrical and magnetic properties of the sample, which are dependent on their permeability and dielectric constant. So, this study will verify the values obtained before. Next, the energy stored in a capacitor is directly proportional, and its size is inversely proportional to the dielectric constant. Similarly, the resistance offered by a material to the magnetic field to pass through it is related to permeability. This study will focus on the variation of impedance with Co2+ concentration. The results were derived with the equivalent circuit model. The impedance analysis is also important in the biological field having a name of Bio-Impedance Analysis (BIA), for determining nutritional status, and many more.