Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 28: Poster Session on Ferroic Domain Walls - Multiferroics (jointly with DF, KR, MA)

TT 28.6: Poster

Montag, 16. März 2015, 19:00–21:00, Poster C

Raman Spectroscopy and Spin-Phonon-Coupling of Multiferroic Eu_1−xHo_xMnO₃ — •Sebastian Elsässer¹, Jean Geurts¹, Vladimir V. Glushkov², and Anatoly M. Balbashov² — ¹Exp. Phys. III, University of Würzburg, Germany — ²Prokhorov GPI, Russian Academy of Sciences, Moscow, Russia

The revival of studies on magneto-electric (ME) effects has led to rich insights in the physics of charge and spin degrees of freedom and their mutual interaction via ME coupling [1]. One of the most extensively studied effects is the inverse Dzyaloshinskii-Moriya interaction. Hereby, the ordering of the magnetic moments leads to a lattice distortion which, in turn, can induce in a permanent electric polarization. This manifests itself in the perovskite-like rare-earth manganites RMnO₃. Here, the average size of the rare-earth ions R³⁺ directly influences the octahedron tilting angle. This can be used to tune the coupling between the magnetic Mn sites yielding model system for the interplay of crystalline distortion, magnetic frustration and electric polarization. In this study, R= Eu³⁺ ions are partially replaced with Ho³⁺ (<30%) to achieve the multiferroic phase. Spin-phonon-coupling (SPC) is probed by temperature-dependent Raman spectroscopy. We identify the elusive peak at  650cm⁻¹ to be the B_3g(1) mode. Upon cooling renormalisation of phonon energies due to SPC-effects starts already well above T_N. We observe that the SPC-shift is mode-specific, being strongest (up to 1%) for the B_2g(1) and B_3g(1), which are both octahedron breathing modes.

[1] M. Fiebig, Journal of Physics D-Applied Physics 38, 8 (2005)