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Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 19: Poster I (Bio- and Molecular Magnetism/ Magnetic Particles and Clusters/ Micro- and Nanostructured Magnetic Materials/ Magnetic Materials/ Multiferroics/ Magnetic Shape Memory Alloys/ Electron Theory of Magntism/ Spincaloric Transport/ Magnetic Coupling and Exchange Bias/ Magnetization Dynamics/ Micromagnetism and Computational Magnetics)

MA 19.46: Poster

Tuesday, March 15, 2011, 10:45–13:00, P2

Coupling Effects between Lattice dynamics and Magnetism in GdMnO3 studied by optical spectroscopySven Issing1, Michael Schmidt2, Franz Mayr2, Joachim Deisenhofer2, Alois Loidl2, Alexander A. Mukhin3, Andrei Pimenov4, and •Jean Geurts11Experimentelle Physik III, Universität Würzburg, Germany — 2Experimentelle Physik V, Universität Augsburg, Germany — 3General Physics Institute of the Russian Academy of Sciences, Moscow, Russia — 4Institut für Festkörperphysik, Technische Universität Wien, Austria

We present detailed optical reflectivity FT-IR investigations of the temperature dependence of the infrared active phonons in the multiferroic manganite GdMnO3 from T = 300K down to T = 5K. GdMnO3 is in the focus of interest due to its intimately coupled orbital, lattice and spin degrees of freedom and the resulting multiferroism. Our results clearly show two different coupling effects shifting the phonon frequencies at the onset of the magnetically ordered phases: Spin-Phonon Coupling (SPC) and Electromagnon-Phonon Coupling (EMPC). SPC is caused by a modulation of the magnetic exchange by a movement of the O2− ions within the MnO2 plane. Thus, it is most strongly pronounced for phonons consisting mainly of distortive modes of the MnO6 octahedra within this plane. We observed a softening of the phonon frequencies by Δ ω ≈ −(1−2)%. EMPC on the other side manifests itself as a strong hardening of the phonon frequency (Δ ω ≈ + 3%) for the B3u(1) mode, which is mainly a Gd3+ and Mn3+ displacement. It is clearly connected with the appearance of the Electromagnon.

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