Defect engineering and magnetic properties of Cu/Cr codoped ZnO nanoparticles

The function of intrinsic defects in controlling the microstructural and magnetic characteristics of sol-gel produced Zn_{0.99 −x}Cu_0.01Cr_xO nanoparticles (x = 0.01–0.05) is methodically examined in this work. For every composition, a single-phase wurtzite structure was verified by Rietveld refinement and X-ray diffraction. Reliable size-strain estimates that demonstrated strong agreement with the Debye-Scherrer approach were produced by Williamson-Hall analysis using the Uniform Stress Deformation Model (USDM). Znᵢ-related violet emission predominated in all samples, V_Zn signatures peaked at x = 0.02, and Oᵢ contributions increased for x ≥ 0.03, indicating a definite reliance on dopant concentration, according to photoluminescence (PL) deconvolution. Electron Spin Resonance (ESR) spectroscopy showed a spin density maximum at x = 0.05 and a narrowing linewidth (ΔH_pp from 97.9 to 81.3 mT) with a single, strong resonance (g = 2.078–2.170) between 300 and 350 mT. The findings demonstrate that the magnetic response and visual PL properties are co-governed by the Znᵢ/V_Zn/Oᵢ defect populations. Additionally, the Cu/Cr co-doped nanoparticles' proven room-temperature ferromagnetism emphasizes its potential for spintronic devices with controllable optical emission.