Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique
TT 16.58: Poster
Samstag, 5. März 2005, 11:00–16:30, Poster TU C
Optical and magnetic properties of low-dimensional perovskite-related (La,Ca)TiO3.4±δ — •K. Thirunavukkuarasu1, F. Lichtenberg2, and C. A. Kuntscher1 — 11. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany — 2Experimentalphysik VI, EKM, Universität Augsburg, 86135 Augsburg, Germany
The perovskite-related titanium oxides LaTiO3.5−x with 0≤x≤0.5 show a rich phase diagram, including a Mott-Hubbard insulator with antiferromagnetic ordering (x=0.5), metallic phases, semiconductors, and a ferroelectric insulator (x=0) [1]. In particular, for x≈0.1 the dc resistivity is strongly anisotropic, with metal-like values along the a axis. The optical conductivity spectrum contains a Drude component only for the polarization E∥a, indicating the quasi-one-dimensional metallic character of LaTiO3.4 [2].
We carried out polarization-dependent infrared reflectivity measurements and magnetic susceptibility measurements on various (La,Ca)TiO3.4±δ single crystals. For all studied crystals the optical conductivity along the chain direction a consists of a Drude-like contribution superimposed by phonon modes, and a pronounced band in the midinfrared range centered at 2000-3000 cm−1(≈250-370 meV). For increasing carrier doping or decreasing temperature a shift of the midinfrared band towards lower frequencies is observed. These findings are discussed in terms of polaronic models.
[1] F. Lichtenberg et al., Prog. Solid State Chem. 29, 1 (2001).
[2] C. A. Kuntscher et al., Phys. Rev. B 67, 035105 (2003).