Self-organized assembly and properties of ferromagnetic metal/semiconductor nanocomposites

The control over the assembly of magnetic cations in semiconductor alloys is of paramount significance for the realization of nanocomposite systems consisting of ferromagnetic metal-compound nanostructures embedded coherently in a semiconducting host, for which a number of functionalities awaits experimental demonstration. A structural and chemical analysis at the nanoscale, and the correlation with macroscopic properties in the model system (Ga,Fe)N, allow us to give experimental evidence that the aggregation of transition metal ions, and consequently the magnetic and optical response, are affected in a controllable way by the fabrication parameters and by co-doping with shallow impurities. The impact of these findings on the search for the origin of high temperature ferromagnetism in magnetically doped semiconductors and oxides is discussed.