The structural, electronic and magnetic properties of the 3d TM (V, Cr, Mn, Fe, Co, Ni and Cu) doped ZnO nanotubes: A first-principles study

We have performed the first-principles calculations onto the structural, electronic and magnetic properties of seven 3d transition-metal (TM=V, Cr, Mn, Fe, Co, Ni and Cu) atom substituting cation Zn in both zigzag (10,0) and armchair (6,6) zinc oxide nanotubes (ZnONTs). The results show that there exists a structural distortion around 3d TM impurities with respect to the pristine ZnONTs. The magnetic moment increases for V-, Cr-doped ZnONTs and reaches maximum for Mn-doped ZnONTs, and then decreases for Fe-, Co-, Ni- and Cu-doped ZnONTs successively, which is consistent with the predicted trend of Hund's rule for maximizing the magnetic moments of the doped TM ions. However, the values of the magnetic moments are smaller than the predicted values of Hund's rule due to strong hybridization between p orbitals of the nearest neighbor O atoms of ZnONTs and d orbitals of the TM atoms. Furthermore, the Mn-, Fe-, Co-, Cu-doped (10,0) and (6,6) ZnONTs with half-metal and thus 100% spin polarization characters seem to be good candidates for spintronic applications.