Comprehensive analysis of Cu-doped CoFe2O4 nanocrystals: Structural, morphological, optoelectronic, and magnetic properties

The aim of this research is to fabricate nanocrystalline ${Cu}_x{Co}_{1-x}{Fe}_2{O}_4$ materials, where x takes values of 0.1, 0.3, and 0.5, and to analyse how their structural, morphological, optoelectronic, vibrational, and magnetic properties change with varying levels of Cu²⁺ doping. The preparation of copper-doped cobalt ferrite samples was conducted using the sol–gel method, with citric acid serving as a chelating agent. Powder X-ray diffraction measurements were conducted to identify the phase and structural attributes of the synthesized copper-doped cobalt ferrite. The Rietveld refinement clearly indicates the single-phase cubic structure, characterized by the Fd-3 m space group. The Debye Scherrer formula was used for the calculation of the crystallite size and it was discovered that the average crystallite size varied from ∼ 4.5 to 5.4 nm (which is less than 10 nm) as the doping concentration of Cu²⁺ was increased. For the surface morphological studies, Field Emission Scanning Electron Microscopy (FESEM) was used, which suggest that all samples are well prepared and are spherical in nature. EDAX analysis validated the elemental composition with appropriate doping in crystalline samples of ${Cu}_x{Co}_{1-x}{Fe}_2{O}_4$. The existence of different chemical bonds has been verified by the Fourier Transform Infrared Rays (FTIR) Spectroscopy. The Raman spectra analysis indicated the existence of various vibrational modes within the sample, revealing the presence of four distinct Raman modes: A1g, Eg, and 2 T2g. Further, the Photoluminescence spectroscopy (PL) was utilized to explore the luminescent properties of the synthesized sample. The optical characteristics was studied using UV–Visible spectroscopy and it was observed that with an increase in the Cu²⁺ concentration, the band gap decreased from 2.466 eV to 2.299 eV. X-ray photoelectron spectroscopy (XPS) was used to analyse the chemical states of the elements present in ${Cu}_x{Co}_{1-x}{Fe}_2{O}_4$ nanoparticles. Furthermore, the magnetic characteristics of the synthesized copper-doped cobalt nanoferrites were examined using a Vibrating Sample Magnetometer (VSM). The hysteresis curves demonstrated low coercivity (H_c) and negligible remanent magnetization (M_r), suggesting the presence of superparamagnetic behavior at room temperature.