This paper presents the co-relation between doping induced defects, structural, magnetic and optical properties of chemically grown Mn doped ZnO nanocrystals. The solubility limit of Mn in ZnO is found to be ∼10%. X-ray diffraction (XRD), Raman spectroscopy and high resolution transmission electron microscope (HRTEM) are employed to study the doping induced defects. These studies confirm that undoped and Mn doped (up to 10%) nanoparticles have lesser defects as compared to 15–20% Mn doped nanocrystals. Noticeable increases in strain with a significant decrease in lattice parameters and bond length were observed for nanocrystals doped with 10% or higher Mn concentrations. In contrast to previous observations of room temperature ferromagnetism in undoped ZnO nanoparticles, we observe diamagnetic behavior of the sample due to lesser oxygen vacancies in these samples. Doped samples show room temperature ferromagnetism and as Mn concentration increases, saturation magnetization decreases due to enhanced anti-ferromagnetic interaction between Mn–Mn ions. Luminescence studies show a significantly visible change in the emission (bright blue → bright green) characteristics with increasing dopant concentration. Currently, LEDs giving UV emission have been combined with broadband visible green phosphors to make white-light LEDs. Thus observed magnetic and optical properties could be utilized in different opto-electronic, dilute magnetic semiconductors (DMS)/spintronics and bio-imaging applications, underlying the findings and importance of current investigations.
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