Electron spin resonance and photoluminescence studies of Co/Mg co-doped ZnO nanoparticles

Zn0.95-xMg0.05CoxO (x = 0.01-0.05 with an increment of 0.01) nanoparticles were synthesized by using the sol-gel technique to analyze structural and magnetic properties. The single phase was observed in the X-ray diffraction measurements. To examine the surface morphology, elemental compositions, crystal quality, defect type, density, and magnetic behavior of the nanoparticles, SEM, energy dispersive X-ray analysis (EDX), PL, and ESR were used, respectively. The PL has ultraviolet and a broad emission band including violet and a blue spectral region corresponding to the defect-related and excitonic emissions. These emissions were strongly dependent on the synthesize condition and doping element and ratio. The effect of cobalt concentration on the line widths of pike to pike (Delta HPP) and the g-factor of ESR spectra were investigated. By comparing the results of the ESR and PL measurements, it was determined which defect with a given g-factor was responsible for the corresponding PL emission band. In addition, ESR spectra of Mg/Co co-doped ZnO nanoparticles with different cobalt concentrations recorded at room temperature were presented. Since Mg/Co co-doped ZnO nanoparticles reveal ferromagnetism at RT, they could be an appropriate material for new devices in spin-based technologies.