Role of divalent Co²⁺ and trivalent Tb³⁺ incorporation in ZnO nanocrystals: Structural, optical, photoluminescence properties and enhanced ferromagnetism

Herein, we synthesized the series of cobalt (Co) and terbium (Tb) co-doped (Zn_0.95-xTb_xCo_0.05O; x = 1–4%) nanocrystals by co-precipitation method and studied their multifunctional properties. X-ray photoelectron spectroscopy (XPS) results ensure the successful doping of Co and Tb ions in the ZnO lattice. X-ray diffraction (XRD) patterns reveal the formation of single-phase hexagonal wurtzite structure for all samples. Scanning electron microscopy (SEM) analysis shows the non-uniform distribution of spherical-shaped nanocrystals of 20–23 nm size. The UV–visible spectra show a marginal red shift in the absorption peak and a decrease in the bandgap energy. Photoluminescence (PL) spectra show a broad emission band identifying the presence of lattice defects in the visible region those act as trap centers. The magnetic measurements exhibit strong ferromagnetism (FM) at room temperature. The BMPs concentration (10²¹cm⁻³) in the co-doped samples is higher than the required threshold value. It is established that the observed FM is induced by the magnetic polarons.