Identifying properties of Co-doped ZnO nanowires from first-principles calculations

• The ferromagnetic (FM) coupling of configuration I is the most stable.
• The FM coupling between the two Co is mediated by O atom.
• The magnetic moment comes from the Co 3d states.
• The optical properties of Co-doped ZnO nanowires exhibit a blue shift.
• The results indicate that Co-doped ZnO nanowires are magneto-optical materials.

The structural, optical and magnetic properties of Zn46Co2O48 nanowires are studied by first-principles calculations. The energy calculated results show that ferromagnetic coupling is the most stable for two Co atoms substituting for two Zn atoms at inner layer along the [0001] direction (configuration I). The ferromagnetic coupling between Co atoms is mediated by the nearest neighbor oxygen atom as evidenced from the strong spin hybridization between Co 3d and O 2p state near the Fermi level, while the antiferromagnetic coupling is extremely fairly weak spin polarization. It is found that Zn46Co2O48 nanowires have the largest magnetic moment mainly come from Co 3d and a fraction O 2p state. Furthermore, the optical properties of Zn46Co2O48 nanowire exhibit a marked blue-shift, and ultraviolet broad emission from 50 to 380 nm is founded in Zn46Co2O48 nanowire. The above results show that Zn46Co2O48 nanowires are a new type of magneto-electric and magneto-optical materials.