Annealing Temperature Effects on Structural, Magnetic, and Optoelectronic Properties of Mixed Ni_0.6Mg_0.2Co_0.2FeCrO₄ Ferrites

An investigation of the structural, morphological, magnetic, and optical properties of Ni_0.6Mg_0.2Co_0.2FeCrO₄ spinel ferrites prepared by the sol–gel method at different annealing temperatures conducted. The grain size and the unit cells parameters of the synthesized samples exhibit an increasing trend as the annealing temperature increases. A low coercive field was obtained from the hysteresis loops, making Ni_0.6Mg_0.2Co_0.2FeCrO₄ ferrites suitable candidates for soft magnetic devices. The bands associated with the tetrahedral (A) and octahedral [B] sites shift toward higher wavenumbers as the annealing temperature increases. In addition, the optical band gap energy decreases with annealing temperature due to the increase in grain size. From the absorbance and the Tauc method, the samples present direct optical transitions. Moreover, the determined Urbach energies are significantly low and decrease with annealing temperature. This implies that the degree of disorder and defects in the prepared samples decreases by increasing the annealing temperature. A detailed study has also been conducted on the variations versus wavelength of penetration depth, refractive index, extinction coefficient, dielectric constants, conductivity, and loss factor. From the variations of these optical parameters, some interesting optoelectronic applications were deduced for the prepared samples.