Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Correlated Electrons: Poster Session
TT 32.75: Poster
Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B
Optical spectroscopy on multiferroic MnWO4 — •Thomas Möller1, Joachim Hemberger1, Markus Grüninger1, Andrei Pimenov2, Alexey Shuvaev2, Petra Becker-Bohatý3, and Ladislav Bohatý3 — 12. Physikalisches Institut, Universität zu Köln — 2Experimentelle Physik 4, Universität Würzburg — 3Institut für Kristallographie, Universität zu Köln
MnWO4 (Huebnerite) crystallizes in a monoclinic crystal structure composed of alternating layers of Mn2+ and W6+ ions which are octahedrally coordinated by oxygen ions. The partially frustrated spin system exhibits a negative Curie-Weiss temperature TCW ≈ −75 K in the paramagnetic regime and undergoes a sequence of transitions into complex antiferromagnetic phases below TN ≈ 13.5 K, including transitions from commensurate to incommensurate and collinear to non-collinear magnetic order, which are connected to the onset or decay of ferroelectric polarization [1]. Thus MnWO4 belongs to the class of multiferroics. We present a detailed study of the phonon modes of this compound based on polarized reflectivity measurements in the FIR and MIR regime. In addition, polarized transmission measurements in the sub-mm regime below the phonon frequencies have been carried out in order to investigate the low-energy magnetoelectric excitations, so-called electro-magnons [2,3].
[1] A.H. Arkenbout et al., Phys. Rev. B 74, 184431 (2006);
[2] A. Pimenov et al., Nature Phys. 2, 97 (2006);
[3] D. Senff et al., Phys. Rev. Lett. 98, 137206 (2007).