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SYSP: Spintronics in Grundlagen und Anwendungen

SYSP I: HV I

SYSP I.1: Hauptvortrag

Donnerstag, 14. März 2002, 09:30–10:00, H1

Ferromagnetism in (III,Mn)V Semiconductors — •Jürgen König — Institut für Theoretische Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe

Carrier-induced ferromagnetism has been observed in several (III,Mn)V semiconductors. We review the theoretical picture of these ferromagnetic semiconductors that emerges from a model with kinetic-exchange coupling between localized Mn spins and valence-band carriers. We discuss the applicability of this model, the validity of a mean-field approximation widely used in the literature, and validity limits for the simpler RKKY model. Our conclusions are based in part on our analysis of the system’s elementary spin excitations. We use theoretical estimates of spin-wave energies and Monte-Carlo simulations to address the effect of collective fluctuations, neglected by mean-field theory, on limiting the critical temperature. Furthermore, we provide a microscopic theory for phenomenological micromagnetic parameters and evaluate them using either simple or more sophisticated models for the band-structure of the host material. As an application we discuss recently measured domain structures in films of (Ga,Mn)As.

Collaborators in different parts of the presented work has been T. Dietl, T. Jungwirth, H.H. Lin, A.H. MacDonald, and J. Schliemann.