Effect of 3d-transition metal atoms distribution on exchange interaction and optical spectra in the diluted magnetic semiconductors of III–V and IV groups

We calculated the total energy of ferromagnetic (FM) and antiferromagnetic (AFM) GaN:Mn, GaAs:Mn, Ge:Mn and Si:Mn with various distribution of Mn atoms. It is found that the formation of Mn–N–Mn–N chain-like fragments largely lowers the total energy of GaN:Mn. Exchange interaction in the chains has AFM character, so this mechanism can result in a significant decrease of the Curie temperature of GaN:Mn. Our optical calculations show that the formation of such chain-like fragments introduces features in intragap absorption and can be observed in optical measurements. In GaAs:Mn, Ge:Mn and Si:Mn this mechanism is not efficient and the formation of the chains of Mn atoms has no significant effect on Curie temperature.