Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.111: Poster

Wednesday, March 29, 2006, 14:30–18:30, P1

Role of the structural distortions in the phase diagrams of RE_1−xA_xTiO₃ (A=Ca,...) — •A. C. Komarek¹, M. Cwik¹, W. D. Stein¹, H. Roth¹, H. Hartmann¹, T. Zabel¹, M. Kriener¹, N. Schittner¹, A. El-Filali¹, M. Hölzel², F. Bouree³, T. Lorenz¹, A. Freimuth¹, and M. Braden¹ — ¹II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln — ²Technische Universität Darmstadt, c/o Technische Universität München — ³Laboratoire Leon Brillouin, CE-Saclay, F-91191 Gif-sur-Yvette, France

Having one electron in the 3d shell, the rare earth (RE) titanates RETiO₃ represent interesting systems to study the complex interplay of orbital and magnetic degrees of freedom as well as to investigate metal-insulator (MI) transitions enabled by hole doping due to a partial substitution of the trivalent rare earth by divalent earth alkaline ions. In the series of rare earth titanates we find an anomalous behaviour of the lattice parameter a for the samples with larger rare earth ions showing antiferromagnetic order. However, with decreasing rare-earth ionic radius the anomalous increase of the lattice constant a gets even more pronounced and sets in closer to the magnetic ordering temperature. The hole-doped system Y_1−xCa_xTiO₃ shows a complex phase diagram of structural transitions. The structural changes are accompanied by a MI transition and anomalies in the magnetic susceptibility. We ascribe this complex behavior to the coexistence of an insulating monoclinic phase and a metallic low-temperature orthorhombic phase. Our neutron diffraction data give evidence for a charge ordering in the monoclinic phase.