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 15.111: Poster
Dienstag, 27. März 2007, 15:00–19:00, Poster A
Disordered Correlated Kondo-lattice model — •Vadym Bryksa and Wolfgang Nolting — Institut für Physik, Humboldt-Universität zu Berlin, Theoretische Festkörperphysik, Newtonstraße 15, D-12489 Berlin
We propose a self-consistent approximate solution of the disordered Kondo-lattice model (KLM) to get the interconnected electronic and magnetic properties of ’local-moment’ systems like diluted ferromagnetic semiconductors. Aiming at compounds (A1−xMx) , where magnetic (M) and non-magnetic (A) atoms are distributed randomly over a crystal lattice, we present a theory which treats the subsystems of itinerant charge carriers and localized magnetic moments in a homologous manner. The coupling between the localized moments, being mediated by itinerant electrons (holes), is treated by a modified RKKY-theory which maps the KLM onto an effective Heisenberg model. The exchange integrals turn out to be functionals of the electronic selfenergy guaranteeing selfconsistency of our theory. The disordered electronic and moment systems are both treated by CPA-type methods. We discuss in detail the dependencies of key-terms such as the long range and oscillating effectice exchange integrals, ’the local-moment’ magnetization, the electron spin polarization, the Curie temperature as well as the electronic and magnonic quasiparticle densities of states on the concentration x of magnetic ions, the carrier concentration n, the exchange coupling J, and the temperature. The disorder causes anomalies in the spin spectrum especially in the low-dilution regime, which are not observed in the mean field approximation.