Characteristics of the incorporation of Yb defect states in CuO:ZnO nanocomposite

Exploring magnetic order in nonferromagnetic substances, such as CuO:ZnO, becomes especially attractive when introducing defect states through nonmagnetic ion doping. In this study, we delved into the impact of Yb doping on the structural, morphological, optical, and magnetic properties of CuO:ZnO. The Yb doped CuO:ZnO was prepared with different Yb concentrations (x = 0.00–20 %) via the temperature-assisted co-precipitation method. X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, and vibrating sample magnetometer (VSM) were used to investigate the structural, morphological, optical, and magnetic properties of Yb doped CuO:ZnO nanocomposites. The incorporation of Yb in CuO:ZnO nanocomposites leads to a notable shift of the characteristic XRD peaks of CuO and ZnO to lower angles, accompanied by an increase in the lattice parameters. UV–visible absorption spectroscopy shows an overall decrease in the optical band gap energy of ZnO as the Yb defect level increases. FE-SEM studies revealed the transformation of spherical structures into agglomerated non-spherical structures upon the introduction of Yb ions into CuO:ZnO nanocomposites. According to XPS data, the predominant valences of Yb-doped CuO:ZnO nanocomposites are Zn²⁺, Cu²⁺, and Yb³⁺. One noteworthy observation from the XPS results is that, in comparison to the intensity of O_L or O_ad peaks, the intensity of O_V (Oxygen vacancy) defect peak increases when the Yb impurity concentration increases. Magnetic measurements demonstrated a diamagnetic order in pure ZnO, which converts to a ferromagnetic order with the incorporation of Yb defect states. The ferromagnetic properties of the Yb-doped CuO:ZnO nanocomposite can be ascribed to the exchange interaction of Yb³⁺ ions with defect states (Oxygen Vacancy) in ZnO and CuO.