Regensburg 2010 – wissenschaftliches Programm

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KR: Fachverband Kristallographie

KR 10: Poster: Multiferroics (with MA, DF, KR, DS)

KR 10.19: Poster

Dienstag, 23. März 2010, 10:45–13:45, Poster A

Influence of doping on the lattice dynamics: Comparison of stoichiometric and mixed orthorhombic rare earth manganites RMnO₃ (R = Gd, Tb, Eu:Y) — •S. Issing¹, F. Fuchs¹, C. Ziereis¹, E. Batke¹, A. Pimenov¹, Y. Vu. Ivanov², A. A. Mukhin², and J. Geurts¹ — ¹Physikalisches Institut, Universität Würzburg, Germany — ²General Physics Institute of the Russian Academy of Sciences, Moscow, Russia

Among the class of multiferroics, the orthorhombic manganites RMnO₃ are an excellent example for the intimate coupling of lattice and magnetic degrees of freedom. For a fine tuning of the magnetic properties the isovalent substitution of the R ion can be employed leading to a quasi-continuous increase of the orthorhombic crystalline distortion and thus of the magnetic frustration responsible for multiferroicity. However the question of disorder induced by isovalent substitution needs to be adressed. Thus, employing Raman and FTIR spectroscopy, we studied the lattice dynamics of stoichiometric (R = Eu, Gd, Tb) as well as mixed RMnO₃ compounds (Eu_1−xY_x 0≤x≤0.5 - covering the R ion radius from Eu to Tb) - to gain insight into the consequences of an isovalent partial substitution on the R-site. Our spectroscopic techniques give us sensitivity not only to symmetry properties but also to the involvement of different ion types within the unit cell. Our results clearly show that the MnO₆-octahedra remain unaffected by disorder, making Eu_1−xY_xMnO₃ an excellent model system for a quasi-continuous fine-tuning of the lattice properties relevant for the appearance of multiferroicity.