Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 34: Correlated Electrons: Metal-Insulator Transition 2
TT 34.8: Vortrag
Donnerstag, 28. Februar 2008, 16:00–16:15, H 2053
Charge ordering in perovskite rare-earth titanate compounds — •A. C. Komarek1, M. Reuther1, N. Hollmann1, A. Cousson2, F. Bouree2, M. Hölzel3,4, A. Senyshyn3,4, P. Link3, D. Trots5,4, C. Baehts5,4, T. Lorenz1, and M. Braden1 — 1Institute of Physics II, University of Cologne, Cologne — 2LLB, CEA/CNRS, Saclay — 3TU Munich, FRM-II, Garching — 4Institute for Materials Science, TU Darmstadt, Darmstadt — 5Hasylab/DESY, Hamburg
Having a single electron in the 3d shell, the rare-earth (RE) titanates RETiO3 have attracted strong interest to study the complex interplay of charge, orbital and magnetic degrees of freedom. Substituting divalent earth-alkali for the RE, a metal-insulator transition is induced, which in case of Y1−xCaxTiO3 occurs only at rather high doping. We have studied the hole-doped system (Y,Er,Lu)1−xCaxTiO3 by various diffraction techniques, by resistivity and by magnetic susceptibility measurements. This system shows a complex phase diagram of structural distortions accompanied by a metal-insulator transition. We ascribe the complex behavior to the coexistence of an insulating monoclinic phase with a metallic low-temperature orthorhombic phase. Our neutron diffraction data show that charge ordering occurs in the monoclinic phase. Even away from half-doping, we find two distinct Ti sites in a checkerboard arrangement, with significantly different TiO6 coordination.