Structural, Microstructural, and Magnetic Properties of Cu/Eu Co-Doped ZnO Nanoparticles

Cu/Eu co-doped ZnO nanoparticles with the nominal composition Zn0.99−xCu0.01EuxO (x = 0.00–0.05) were synthesized using the sol–gel method to systematically investigate the influence of Eu incorporation on their structural, microstructural, and magnetic properties. X-ray diffraction (XRD) analysis combined with Rietveld refinement confirmed the predominance of the hexagonal wurtzite ZnO structure, with no detectable secondary crystalline phases within the detection limits of XRD. Crystallite size, lattice strain, stress, and deformation energy density were evaluated using the Debye–Scherrer method and three Williamson–Hall approaches: the Uniform Deformation Model (UDM), Uniform Stress Deformation Model (USDM), and Uniform Deformation Energy Density Model (UDEDM). The crystallite size estimated using the Debye–Scherrer method decreased from 41.13 nm at x = 0.00 to 34.35 nm at x = 0.04, indicating composition-dependent changes in crystal growth. Magnetization–field (M–H) and magnetization–temperature (M–T) measurements were performed between 10 and 300 K using a Physical Property Measurement System (PPMS). The magnetic measurements revealed predominantly paramagnetic behavior at room temperature and enhanced ferromagnetic-like interactions at low temperatures with increasing Eu incorporation. The novelty of this study lies in the combined evaluation of concentration-dependent lattice distortion, microstructural parameters, and magnetic behavior in Cu/Eu co-doped ZnO nanoparticles using complementary structural and magnetic characterization approaches. These findings provide insight into the relationship between dopant concentration, crystal defects, and magnetic interactions, which may inform the development of ZnO-based functional magnetic nanomaterials and their potential use in spintronic applications.