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DS: Fachverband Dünne Schichten
DS 10: Multiferroics II: Hexagonal manganites / Incommensurate multiferroics (jointly with MA, DF, KR, TT)
DS 10.7: Vortrag
Montag, 26. März 2012, 16:45–17:00, EB 301
Theoretical study of Magnetoelectric effects in Multiferroic RMn2O5 — •Safa Golrokh Bahoosh1, Julia Wesselinowa2, and Steffen Trimper3 — 1Max Planck Institute of Microstructure Physics, 06099 Halle, Germany — 2Department of Physics, University of Sofia, 1164 Sofia, Bulgaria — 3Institute of Physics, Martin-Luther-University, 06120 Halle, Germany
The magnetoelectric behavior of the rare-earth RMn2O5 perovskites is studied theoretically using a quantum model. Whereas the magnetic subsystem is described by nearest-neighbor ferromagnetic coupling and next nearest neighbor antiferromagnetic order, the ferroelectric subsystem is characterized by an Ising model in a transverse field.
Due to frustration, the magnetic system offers spiral structures. The coupling between both systems is a symmetry-allowed linear coupling.
Using Green*s functions we find analytically the temperature and wave vector dependent elementary excitation of the Magnetoelectric system, the polarization and the magnetization for different magnetoelectric coupling strengths.
Lowering the temperature, the system undergoes a magnetic transition at TN and a further reduction of the temperature leads to a ferroelectric transition at TC < TN. The magnetoelectric coupling is manifested as a kink in both the magnetization and the elementary excitation at TC. The polarization is enhanced under the presence of a finite external magnetic field. In the same manner the magnetization is slightly changed by an applied electric field near to TC.