Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.72: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

Structural properties of RETiO₃ and Y_1−xCa_xTiO₃ — •A. Komarek¹, H. Roth¹, T. Lorenz¹, W.D. Stein¹, M. Cwik¹, F. Bourée², A. Freimuth¹, and M. Braden¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²Laboratoire Léon Brillouin

We have studied the crystal structure of the RETiO₃ by different diffraction techniques as function of temperature. In all compounds we find significant distortions of the TiO₆-octahedra which lead to a lifting of the t_2g-orbital degeneracy. A comparison with literature data on isostructural compounds with a 3d⁰ or a 4d⁰-configuration shows that such distortions not necessarily are caused by orbital physics. In the RETiO₃-series, however, the temperature dependence clearly points to a direct coupling. The octahedron distortions depend more sensitively on temperature than the tilt and rotation angles; and, in particular, we find strong anomalies at the Néel-temperatures in all antiferromagnetic RETiO₃ compounds.

Neutron diffraction on a sample of Y_0.62Ca_0.38TiO₃ yields strong evidence for charge ordering, which may be the key element to understand, why Ca-doped YTiO₃ stays non-metallic till rather high doping.