Synthesis and influence of Zn substitution on optical and magnetic properties of cobalt ferrite nanoparticles by a polyacrylamide gel route

Zn-doped CoFe₂O₄ nanoparticles were prepared via a modified polyacrylamide gel method. X-ray diffraction (XRD) and Fourier transform infrared spectrometer (FTIR) data reveal the formation of cubic spinel phase Co_1−xZn_xFe₂O₄ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) with average crystallite sizes from 57 to 44 nm. X-ray photoelectron spectrometer (XPS) result declares the compositional stoichiometry and atomic ratios of Co to Zn. Scanning electron microscopy (SEM) images show that the nanoparticles are prone to clustering via agglomeration. High crystallinity and elemental uniformity are demonstrated by transmission electron microscopy (TEM) technique. Ultraviolet–Visible (UV–Vis) diffuse refectance spectroscopy (DRS) measurements determine the optical band gaps from 1.46 to 1.57 eV. The hysteresis loops exhibit that all the products have a ferromagnetic behavior. The concentration of Zn²⁺ doping strikingly affects magnetic properties. The saturation magnetization (M_s) reaches a maximum value of 79 emu/g at x = 0.2. Both coercivity (H_c) and remanent magnetization (M_r) reduce with increasing content of Zn²⁺. The variation mechanism of magnetic properties is discussed. This work will provide a valuable reference for synthesizing doped cobalt ferrite and tuning magnetic properties.