Investigation on Optical, Dielectric, and Magnetic Properties of CoAl_2-xFe_xO₄ Nanoparticles

In this study, Fe³⁺ doped cobalt aluminate, CoAl_2-xFe_xO₄, x = 0.00, 0.05, 0.10, 0.15, and 0.20, nanoparticles are synthesized via an efficient co-precipitation method. X-ray powder diffraction (XRD) is used to confirm the formation of single-phase cubic spinel structure. Some important optical parameters such as optical band gap E_opt, Urbach energy E_u, and refractive index n are estimated using UV-visible spectra, and their variations with Fe³⁺ content are discussed. Dielectric studies are carried out for the pelletized samples of CoAl_2-xFe_xO₄ nanoparticles at room temperature in the frequency range 50 kHz to 5 MHz. Several important dielectric parameters such as dielectric permittivity (ε′), dielectric loss (tanδ), and ac conductivity (σ_ac) of the samples are determined as a function in both frequency and Fe³⁺ content. The obtained Cole–Cole diagram shows one semicircle corresponding to grain conductions. The magnetic hysteresis (M-H) loop shows ferromagnetic behavior of the samples. The results show that the variation of magnetic parameters depends strongly on Fe³⁺ content and particle size. Saturation magnetization, magnetic moment, and remnant magnetization increase as the Fe³⁺ content increases.