Local structure around Mn atoms in room-temperature ferromagnetic (In,Mn)As thin films probed by extended x-ray absorption fine structure

An extended x-ray absorption fine structure technique has been employed to probe the average local structure around Mn impurity atoms in (In,Mn)As thin films prepared by organometallic vapor phase epitaxy. These films show ferromagnetism above room temperature. As the concentration of Mn increases, the average local environment surrounding Mn changes from that of a Mn–Mn interstitial pair to a dimer, trimer, or cubic MnAs structure and then to the hexagonal MnAs structure/interstitial pair. In contrast to random substitution, the Mn impurity atoms in these dimer, trimer, or cubic MnAs structure occupy adjacent sites in the In sublattice. Ferromagnetism above room temperature in these ordered substitutional samples provides an excellent example for ferromagnetic exchange interaction in (In,Mn)As diluted magnetic semiconductors without the formation of hexagonal MnAs clusters, this is potentially very important for spintronic applications.