Tailoring the Magnetic and Optical properties of MgO Nanoparticles by Cobalt doping

 In this work, Cobalt (0-10) % doped MgO nanoparticles are prepared for magnetic and optical studies. X-ray diffraction studies show the particle size increases from 3.10 nm to 9.50 nm with increasing Cobalt concentration in MgO samples. The secondary phases are observed beyond 5% Cobalt in the host MgO which indicates the solubility limit of dopant in this material. SEM analysis further reconfirms the purity and spherical morphology of nanoparticles in all samples. Its result also reveals that the smallest particles have the largest oxygen vacancy concentration as compared to other samples. The dopant and size-induced effects are observed for electronic absorption spectra and bandgap of the samples.  UV-visible absorption spectra show a quantum confinement effect as the optical band gap decreases with the increase of the particle size. The optical band gap of the nanoparticles ranges from 4.68 eV to 3.15 eV which is very less in comparison with the bulk MgO band gap up to 7.2eV.  Vibrating sample magnetometer studies at room temperature clearly show the ferromagnetic behavior for pure MgO nanoparticles in contrast with the paramagnetic behavior for other samples.  It is suggested that the presence of the ferromagnetic behavior in pure MgO nanoparticles are due to the presence of oxygen vacancies.