Ferromagnetism induced by intrinsic defects and carbon substitution in ZnO nanowires

The possibilities of magnetism induced by intrinsic defects and carbon substitution in ZnO nanowires are investigated by ab initio calculations. The calculated results indicate that an ideal ZnO nanowire is nonmagnetic. The zinc (Zn) vacancy can induce the magnetic moments rather than oxygen vacancy, which is originated from the polarization of O 2p electrons. A couple of zinc vacancies can lead to the ferromagnetic coupling. A carbon substitution for oxygen also produces magnetic moments. When substituting two carbon atoms, the characteristics of exchange coupling depend upon the distance of two carbon atoms. The longer distance of two carbon atoms prefers the ferromagnetic coupling, whereas the shorter distance leads to the antiferromagnetic coupling.