Microstructural, magnetic and electrical properties of Zn_0.4M_0.3Co_0.3Fe₂O₄ (M = Ni and Cu) ferrites synthesized by sol–gel method

A comparative study of microstructural, magnetic and electrical properties of Zn_0.4Ni_0.3Co_0.3Fe₂O₄ (ZNCFO) and Zn_0.4Cu_0.3Co_0.3Fe₂O₄ (ZCCFO) ferrites prepared using sol–gel method have been investigated in this work. X-ray diffraction results indicate that samples have cubic spinel type structure (\(Fd\bar {3}m\) space group). Lattice constant, average grain size and X-ray density are higher for ZCCFO than those of ZNCFO. The magnetic parameters such as M _s , H _c , and M _r were found to decrease with the substitution of Ni by Cu. The electrical properties of the samples have been studied using impedance measurements as a function of frequency and temperature. The substitution of Zn–Co ferrite with Cu leads to improve its conductivity that its substitution with Ni. The behaviors of imaginary part of permittivity and loss tangent have been investigated using Maxwell–Wagner’s model and Koop’s theory. The electrical modulus study reveals the presence of the non-Debye type of dielectric relaxation in our samples. Close values of activation energy for dc conduction (E _dc ) and for conductivity relaxation (E _Mʺ ) were found confirming that the relaxation process and electrical conductivity are attributed to the same defect. Nyquist representations (Z″ vs. Zʹ) were plotted and their characteristic behaviors were analyzed in terms of electrical equivalent circuit.