Nanomagnetism in Ge-Doped Narrow CNTs

Abstract

By carrying out density functional theory (DFT) calculations, we studied the effects of Gedoping on the geometrical, electronic, and magnetic properties of carbon nanotubes (CNTs). Three different doping configurations were considered. All of these configurations were stable upon relaxation. It was found that the formation energies of Ge-doped zigzag nanotubes increased with increasing tube diameters, indicating that the doping of Ge into narrower CNTs was more energetically favorable. In the presence of impurity, the electronic properties of small gap semiconducting nanotubes could be changed and the band gap be removed, but the metallic (5, 5) nanotube remained metallic after doping. Spontaneous magnetization was found to be induced in doping Ge nanotubes. The occurrence of ferromagnetism in the absence of transition-metal atoms arose mainly from the Ge-p states and was partially due to C p-orbitals. The magnetic moments of Ge atoms vary with the radius and chirality of nanotubes and their adsorbing sites.