Ferromagnetism in ZnO clusters, due to vacancy defects and C impurities doped at substitutional O or Zn sites, and interstitial sites, was investigated. The total energy calculations suggested that C at the O site was more stable than that at the Zn site in ZnO clusters. The total magnetic moments of ZnnOn−mCm clusters were 2.0μB/C. However, when two C atoms were bonded to the same Zn atom they interacted antiferromagnetically and the total magnetic moment became less than 2.0μB/C. The interstitial C defects in ZnO clusters induce small magnetic moments. The combination of substitutional and interstitial C defects in ZnO clusters led to magnetic moments of 0.0–2.0 μB/C. The presence of vacancy defects in addition to substitutional C defects gave magnetic moments of greater than 2.0 μB/C. These results suggested that the experimentally observed sample dependence of magnetic moments in ZnO systems was largely due to the different concentrations of substitutional and interstitial C impurities and the presence of vacancy defects in ZnO samples prepared under different growth conditions.

Spin-Polarized Density Functional Investigation into Ferromagnetism in C-Doped (ZnO)N Clusters; n = 1–12, 16. H.Sharma, R.Singh: Journal of Physics: Condensed Matter, 2011, 23[10], 106004