Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 2: Correlated Electrons - Metal Insulator Transition

TT 2.5: Vortrag

Freitag, 4. März 2005, 11:15–11:30, TU H2053

Relevance Of Structural Distortions To The Metal Insulator Transition Of Doped LaTiO₃ — •H. Roth¹, K. Kordonis¹, A. Komarek¹, M. Cwik¹, N. Schittner¹, J. Baier¹, M. Kriener¹, T. Lorenz¹, N. Johannsen¹, T. Zabel¹, A. El Filali¹, G. André², M. Braden¹, and A. Freimuth¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²Labaroatore Léon Brilliouin, Saclay

LaTiO₃ is an antiferromagnetic insulator. Hole-doping suppresses T_N and induces a metal-insulator transition (MIT). We present a systematic study of magnetization, specific heat and resistivity of La_1−xSr_xTiO₃ and LaTiO_3+δ. While La_1−xSr_xTiO₃ shows a MIT at a hole concentration n=x ≈ 4 %, the oxygen-doped LaTiO_3+δ stays insulating up to a much higher charge-carrier concentration n=2 δ ≈ 8 % . Thus, the MIT of doped LaTiO₃ cannot be described by band filling alone. X-ray and neutron diffraction show that the orthorhombic splitting є decreases upon doping, too. Both, the magnetic and the metal insulator transition scale with the size of є, indicating that the orbital splitting is crucial for the magnetic and transport behaviour. Another aspect of the MIT in the studied systems is the coexistance of antiferromagnetic order and metallic behaviour in the intermediate doping range ( x ≈ 0.05, 0.04 ≤ δ ≤ 0.1).

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