Effect of Surfactant Treatment on the Magnetic Properties of Mn-Doped ZnO Bulk and Nanoparticles

We report the effect of surfactant treatment on the structural and magnetic properties of Mn-doped ZnO bulk (Zn0.978Mn0.022O) and Mn- and Li-codoped ZnO nanoparticles (Zn0.96Mn0.03Li0.01O) prepared by low-temperature reaction. X-ray diffraction and transmission electron microscopy analyses of these samples showed the formation of impurity-free crystals with wurtzite ZnO structure. XPS data revealed that Mn exists in the 2+ oxidation state. TEM and HRTEM studies of sodium bis-2-ethylhexyl sulfosuccinate (AOT)-treated Zn0.978Mn0.022O showed predominantly rodlike microstructures developing into platelets and sizes in the range of 50-500 nm, whereas the AOT-treated Zn0.96Mn0.03Li0.01O sample showed nearly spherical particles in the nanometer regime (20-30 nm). DC magnetization measurements as a function of field showed enhanced room temperature ferromagnetism for the surfactant-treated Zn0.978Mn0.022O and Zn0.96Mn0.03Li0.01O. We discuss the possible role of surfactant and Li ion on the magnetic properties of Mn-doped ZnO.