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TT: Tiefe Temperaturen

TT 2: Correlated Electrons - Metal Insulator Transition

TT 2.1: Vortrag

Freitag, 4. März 2005, 10:15–10:30, TU H2053

The orbital degree of freedom in single- and bilayered manganites — •M. Merz¹, P. Reutler², B. Büchner², A. Revcolevschi³, Y. Idzerda⁴, S. Tokumitsu⁵, and S. Schuppler⁵ — ¹Inst. für Kristallographie, RWTH-Aachen — ²IFW Dresden — ³Uni. Paris-Sud — ⁴NRL, Washington — ⁵Forschungszentrum Karlsruhe, IFP

Transition metal oxides like the manganites are fascinating materials since their physical properties are intimately connected with an unusual interrelation between spin, charge, and orbital degrees of freedom. Yet, only little is known about the nature of the experimentally observed ordered phases and the principal factors determining the ordering scheme. To better understand the phenomena of charge/orbital ordering (CO/OO) and to isolate the fundamental properties which serve as a driving force for CO/OO we have investigated layered manganites with x-ray diffraction and near-edge x-ray absorption spectroscopy. The current data demonstrate that the energy difference between d_3x²−r², d_3y²−r², and d_3z²−r² orbitals is very small for single- and bilayered systems and indicate that the orbital degree of freedom is determined not only by crystal field effects but also by orbital coupling.