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MA: Fachverband Magnetismus

MA 38: Multiferroics

MA 38.13: Talk

Thursday, March 26, 2009, 18:30–18:45, HSZ 103

Many-particle Approach to Multiferroic Bulk Systems — •Thomas Michael¹, Steffen Trimper¹, and Julia M. Wesselinowa² — ¹Institute of Physics, Martin-Luther-Universitaet, Halle (Saale), Germany — ²Department of Physics, University of Sofia, Sofia, Bulgaria

Multiferroic bulk systems are studied in a many-particle approach. The magnetization, polarization, excitation energies, associated dampings of ferroelectric and magnetic modes are presented as a function of temperature. An anomaly in the ferroelectric quantities close to the magnetic phase transition is observed. The analysis of the ferroelectric subsystem is based on a two-state quantum model, the Ising model in a transverse field. The magnetic moments interact via the Heisenberg model. The corresponding multiferroic coupling term differs for hexagonal and orthorhombic materials. A Green's function technique in reciprocal space provides the static and dynamic properties. Furthermore, we present the dielectric function of the coupled model. The theoretical result are compared with experimental data.