Controlled aggregation of magnetic ions in a semiconductor. Experimental   demonstration
  The control on the distribution of magnetic ions into a semiconducting host is crucial for the functionality of magnetically doped semiconductors. Through a structural analysis at the nanoscale, we give experimental evidence that the aggregation of Fe ions in (Ga,Fe)N and consequently the magnetic response of the material are affected by growth rate and co-doping with shallow impurities. 
A.Bonanni, A.Navarro-Quezada, Tian Li, M.Wegscheider, Z.Matej, V.Holy,   R.T.Lechner, G.Bauer, M.Kiecana, M.Sawicki, T.Dietl