Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)
MA 15.103: Poster
Dienstag, 27. März 2007, 15:00–19:00, Poster A
Exchange constants in Mn doped Ge and GaAs: a first principles study of the environment effects — •Marjana Ležaić1, Silvia Picozzi2, Phivos Mavropoulos1, Yuriy Mokrousov3, and Stefan Blügel1 — 1IFF, Forschungszentrum Jülich, Jülich, Germany — 2CNR-INFM CASTI Regional Lab., L’Aquila, Italy — 3Institute for Applied Physics, University of Hamburg, Hamburg, Germany
Ab-initio calculations have been performed for [001]-ordered Mn/Ge and Mn/GaAs “digital alloys", focusing on the effects of the band-gap width and the semiconducting host on the exchange constants of the Mn atoms. Our results for Mn/Ge, obtained using a frozen-magnon scheme [1], show that a larger band-gap tends to give a stronger nearest-neighbor ferromagnetic coupling and an overall enhanced in-plane ferromagnetic coupling even for longer-ranged coupling constants. Mn/GaAs shows a smaller nearest-neighbor ferromagnetic coupling than Mn/Ge, but exchange constants for higher Mn-Mn distance show an overall increased ferromagnetic behavior in Mn/GaAs [2]. The environmental dependence of the exchange constants in Mn-doped Ge was also investigated. We find that while the exchange constants in [001] and [111] direction remain small and practically unaffected by the different arrangements of the Mn atoms in Ge matrix, the coupling along [110] direction shows a strong environmental and concentration dependence. We discuss the exchange mechanisms and their consequences to the Curie temperature of the alloys.
[1] As implemented in the FLEUR code, http://www.flapw.de
[2] S.Picozzi, M.Ležaić, S.Blügel, Phys.Stat.Sol.(a) 203, 2738 (2006)