Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 31: Matter at Low Temperature: Materials
TT 31.5: Vortrag
Mittwoch, 25. März 2009, 16:45–17:00, HSZ 304
Far-infrared measurements on multiferroic TbMnO3 — •Michael Schmidt, Christian Kant, Torsten Rudolf, Franz Mayr, Joachim Deisenhofer, and Alois Loidl — Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86135 Augsburg, Germany
Recently multiferroics with strongly enhanced magnetoelectric effects attracted considerable attention. Especially TbMnO3 gained a lot of interest, as in this compound it has been documented that spin waves can be excited by ac electric fields. This novel excitations of multiferroics have been termed electromagnons [1].
Despite extensive experimental and theoretical efforts, the microscopic origin of these excitations is strongly debated and their coupling to phonons is not fully understood. New models aiming to explain the origin of these excitations have been developed [2,3].
We performed polarization dependent far-infrared spectroscopy on TbMnO3 for wavenumbers ranging from 40 cm−1 to 8000 cm−1 and temperatures from 5 K to 300 K. We followed in detail the temperature dependencies of eigenfrequencies, strengths and damping constants of all IR-active phonon modes, with the main emphasis to study the coupling of phonons to spin excitations. We provide experimental evidence that the low energy phonon modes are strongly coupled to spin excitations, a characteristic feature of spin driven ferroelectricity.
[1] A. Pimenov et al., Nature Phys. 2, 97 (2006)
[2] Y. Takahashi et al., Phys. Rev. Lett. 101, 187201 (2008)
[3] R. Valdés Aguilar et al., arXiv:0811.2966v1 (unpublished)