Dresden 2006 – wissenschaftliches Programm

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MA: Magnetismus

MA 24: Magnetic Thin Films III

MA 24.3: Vortrag

Donnerstag, 30. März 2006, 10:45–11:00, HSZ 03

EXAFS on electron-doped La_0.7A_0.3CoO₃ — •Christian Pinta^1,2, Dirk Fuchs¹, Eric Pellegrin¹, Peter Adelmann¹, Stefan Mangold³, and Stefan Schuppler¹ — ¹Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe — ²Universität Karlsruhe, Fakultät für Physik,D-76128 Karlsruhe — ³Forschungszentrum Karlsruhe, Institut für Synchotronstrahlung, D-76021 Karlsruhe

Cobaltites are currently receiving intense interest. Especially intriguing is the large number of interactions in this mixed-valent family of compounds (like Hund’s coupling, double exchange, correlation, and crystal field) that occur on similar energy scales and may lead to a number of mutually competing phases. Up until recently it was impossible to dope cobaltites with electrons, and it still is for bulk material. For epitaxial thin-film systems, however, we have performed the first successful synthesis of single-phase electron-doped lanthanum cobaltites, La_1−xA_xCoO₃ (A=Ce or Te). These films exhibit ferromagnetic order with transition temperatures T_C of about 85K and 20K for Te and Ce doping, respectively. To better understand the interplay between local structure, doping, and magnetism, we performed Co K-edge EXAFS measurements on three cobaltite thin-film systems: La_0.7Ce_0.3CoO₃, La_0.7Te_0.3CoO₃, and LaCoO₃. For further comparison to bulk material, we also carried out measurements on powder samples of undoped LaCoO₃. Partial substitution of La by Ce and Te as well as the epitaxial growth clearly affect the local structure; possible implications for the doping-related electronic structure and spin states will be discussed.