Influence of Mn doping on the magnetic and optical properties of ZnO nanocrystalline particles

(a) High resolution Zn 2p core level XPS spectra for ZnxMn1-xO, with x=0.0.8. (b) The UV–Visible diffuse reflectance spectra of Zn1-xMnxO nanoparticles with different Mn doping as a function of wavelength, the insert shows the broad reflection minima in the visible range for the samples with 0.08% Mn. (c) Magnetization hysteresis curves of the Zn1-xMnxO samples with x=0.02, x=0.04, x=0.08, and x=0.1 measured at 10K. (d) The measured coercive fields of the Zn1-xMnxO samples (left y-axis) and the energy gap (right y-axis) as a function of Mn concentration (x). [Display omitted] •Systematic study was done on the influence of Mn-doping on ZnO properties.•The magnetic properties were studied in a wide range of temperatures and fields.•Room temperature ferromagnetism was found in Mn-doped ZnO.•A clear explanation of the magnetic and optical behaviors was introduced. The structural, optical and magnetic properties of Mn doped ZnO nanocrystalline particles, Zn1-xMnxO, with different percentages of Mn content have been studied. XRD and XPS measurements showed that all samples with Mn doping up to x=0.1 possess typical wurtzite structure and have no other impurity phases. The incorporation of Mn ions into the ZnO lattice was also confirmed by FTIR and UV–Vis. spectroscopy results. Both XRD and SEM results indicated a slight decrease in the grain size with increasing the Mn doping level. The XPS results indicated an increase in the oxygen vacancies concentration with increasing the Mn doping level. The magnetization measurements revealed a weak ferromagnetic behavior at room temperature and a clear ferromagnetic behavior with relatively large coercive fields at low temperature. The ferromagnetic order is improved by increasing the Mn doping. In addition, we observed an increase in the concentration of oxygen vacancies, which is also induced by increasing the Mn doping level. A ferromagnetic coupling of the local moment of Mn dopants through the sp-d exchange interaction and oxygen vacancies, in addition to different magnetic contributions due to different forms of Mn ions that coexist in the Mn doped nanoparticles were presented in order to interpret the observed magnetic behavior. We observed a clear red shift in the direct band gap and an increase in the coercive field and saturation magnetization values with increasing the Mn doping level.