Electronic structure and magnetic properties of Mn-doped ZnO nanotubes: An ab initio study

Abstract

The electronic and magnetic properties of pure and Mn-doped armchair and zigzag ZnO nanotubes were studied using density functional theory with the generalized gradient approximation. The calculated results show that all of the pure ZnO nanotubes are nonmagnetic and have relatively uniform band gap of 1.66 eV at Γ-point. Both the armchair and zigzag ZnO nanotubes are found to be direct gap and the band gaps are almost independent of tubular structures. For the Mn-doped ZnO nanotubes, it is noted that the band gaps are influenced by three factors, doping concentration, diameter, and chirality of the tube, while the bond lengths between Zn and O and between Mn and O for these structures are only decided by the diameter of the nanotube. The magnetic moments, however, are independent of the chirality from comparison between armchair and zigzag Mn-doped ZnO nanotube, and mainly governed by the doping concentration and diameter of the nanotube. Furthermore, it is found that large magnetic moments appears in Mn-doped ZnO nanotubes, which are principally due to the hybridization between the O 2p and Mn 3d states by our analysis.