Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 14: Spin Systems and Itinerant Magnets
TT 14.3: Vortrag
Dienstag, 27. März 2007, 14:30–14:45, H19
Magnetic excitations in multiferroic TbMnO3 — •Daniel Senff1, Peter Link2, Klaudia Hradil3, Arno Hiess4, Louis Pierre Regnault4, Yvan Sidis5, Nadir Aliouane6, Dimitri Argyriou6, and Markus Braden1 — 1II. Physikalisches Institut, Universität zu Köln — 2Forschungsneutronenquelle FRM II, TU München — 3Institut für Physikalische Chemie, Universität Göttingen — 4Institut Laue-Langevin, Grenoble / France — 5Laboratoire Leon Brillouin, Saclay / France — 6Hahn-Meitner-Institut, Berlin
Ferroelectricity (FE) in TbMnO3 is intimately coupled to a complex magnetic ordering: The existence of a spontaneous electric polarization is closely correlated with a magnetic transition into an incommensurable spin-spiral structure. The critical excitations at the FE-transition are thus no longer of phononic, as in conventional ferroelectrics, but of magnetic origin.
We present extensive neutron scattering studies on the spin-wave spectrum of TbMnO3 in the para- as well as in the ferroelectric phase [1]. We have identified the different magnon branches of the spiral structure and discus the dispersion, the field and the temperature dependence of the modes most relevant for the FE-transition. Comparing with recent optical experiments we find an excellent agreement and strengthen the interpretation of strongly mixed magnon-phonon excitations, called electromagnons, as proposed by Pimenov et al. [2].
[1] D. Senff et al., cond-mat/0610620, submitted to PRL.
[2] A. Pimenov et al., Nature physics 2 (2005) 97.