Effects of copper substitution on the microstructural, electrical and magnetic properties of Ni0.7Co0.3-⁢x⁢Cu⁢x⁢Fe2O4 ferrites

Spinel ferrites are interesting materials because of their rich physical and magnetic properties. In this study, copper substituted Ni0.7Co0.3-xCuxFe2O4 (x = 0.0, 0.05, 0.1, 0.15 and 0.2) nanoaystalline ferrites were synthesized using the sol-gel method. The X-ray powder diffraction (XRD) patterns showed that all of the samples had a pure single-phase cubic spinel structure with the Fd-3m space group over the whole composition range. The lattice constants, average crystallite size, and grain size were calculated for these compounds based on the XRD patterns and compared with those for nickel ferrite, where most of the values increased with the copper concentration. The DC resistivity increased with the dopant concentration. The magnetic properties were investigated based on the electron spin resonance, which showed that the g-factor decreased in a linear manner as the magnetic field and dopant concentration increased.