Berlin 2008 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
DF: Fachverband Dielektrische Festkörper
DF 11: Dielectric and ferroelectric thin films and nanostructures I
DF 11.3: Vortrag
Mittwoch, 27. Februar 2008, 14:40–15:00, EB 107
Static and Dynamic Properties of Ferroelectric Nanostructures and Multiferroic Bulk Systems: A Multiscale Approach — •Thomas Michael1, Julia Wesselinowa2, and Steffen Trimper1 — 1Institute of Physics, Martin-Luther-University, D-06099 Halle, Germany — 2University of Sofia, Department of Physics, Blvd. J. Bouchier 5, 1164 Sofia, Bulgaria
Ferroelectric nanostructures and multiferroic bulk systems are studied in a multiscale approach. The excitation energy and the associated damping of ferroelectric modes as well as the polarization and the hysteresis are presented as a function of the temperature, the defect concentration, size and shape of the nanomaterials. The softening of the mode is strongly influenced by the kind of doping ions, the surface configuration and the defect composition. The analysis is based on a modified Ising model in a transverse field. A Green’s function technique in real space provides the static and dynamic properties, which differ significantly from the bulk behavior. Additionally a mesoscopic approach is carried out similar to the Landau-Lifshitz equation with Gilbert damping for ferromagnets. The temperature dependence of the damping paramters is discussed. The analysis is extended to multiferroic bulk systems, where the magnetic moments interact via the Heisenberg model and the multiferroic coupling term differs for hexagonal and orthorhombic materials. We present the dielectric function and the dynamic properties of the coupled model. Both, the Green’s function technique and the mesoscopic Landau-Lifshitz equation are applicable here. Theoretical results are compared with experiments.