Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 40: Poster Session Correlated Electrons
TT 40.68: Poster
Wednesday, March 13, 2013, 15:00–19:00, Poster D
Optical phonons in multiferroic CuCrO2, studied by Raman and Far-Infrared spectroscopy — •Michael Eichberger1, Jean Geurts1, Michael Schmidt2, Vladimir Tsurkan2,3, and Joachim Deisenhofer2 — 1Institute of Physics, University of Würzburg, Germany — 2Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, Germany — 3Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Moldova
CuCrO2 is an example for a multiferroic material, in which the ferroelectric order is driven by a proper-screw type magnetic order, occurring below TN ∼ 24 K. While the magnetic order and its coupling with the ferroelectricity has been in the focus of most research activities on this system, we investigated the optical phonons and the possible effect of spin ordering, employing Raman and FIR spectroscopy. As the CuCrO2 crystal structure (space group R3m) has an inversion centre, Raman spectroscopy gives access to the g-modes, while FIR probes the u-modes. All expected optical modes (A1g, Eg, 2A2u, 2Eu) were observed. No mode splitting or emergence of new modes occurs when entering the magnetically ordered state. The Eg mode shows a slight softening in the low temperature range, which may indicate a weak spin-phonon coupling. This mode is modulating the Cr-O bonding and thereby affecting the overlap of the participating wavefunctions. At the same time, this overlap is responsible for the antiferromagnetic interaction between the Cr-atoms and hence establishing the magnetic order within the Cr-plane.