Regensburg 2010 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.4: Poster

Mittwoch, 24. März 2010, 14:00–18:00, Poster D1

X-ray absorption of hole-doped and electron-doped Pr_1−xCa_xMnO₃: Doping-dependent transfer of spectral weight — •Stephan Uebe^1,2, Andrea Assmann^1,2, Michael Merz¹, Prabir Pal³, Manas Dalai³, Biju Sekhar³, Hilbert von Löhneysen^1,2, Peter Nagel¹, and Stefan Schuppler¹ — ¹Karlsruhe Institute of Technology, Institut für Festkörperphysik, Germany — ²Karlsruhe Institute of Technology, Physikalisches Institut, Germany — ³Institute of Physics, Bhubaneswar, India

Transition metal oxides like the manganites have intriguing physical properties, many of which are based on unusual interrelations between spin, charge, and orbital degrees of freedom. To better understand the phenomena of charge/orbital ordering (CO/OO) and to possibly isolate the fundamental properties which serve as a driving force for CO/OO we have investigated Pr_1−xCa_xMnO₃ with temperature-dependent near-edge x-ray absorption spectroscopy. With respect to CO/OO, Pr_1−xCa_xMnO₃ becomes especially interesting since it is a narrow band system with almost identical radii of Pr³⁺ and Ca²⁺. Changes in the tolerance factor can, therefore, directly be attributed to the t_2g and e_g orbital occupation. The present data clearly show that the spectral weight and, thus, the number of unoccupied states near the Fermi energy directly tracks the Ca doping level x. A small but distinct redistribution with temperature between the t_2g and e_g states at E_F is observed. Implications of the spectroscopic data will be discussed.