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Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 57: Focus Session "X-ray absorption spectra - state of the art of theory and experiment" (jointly with DS, HL, MM, O), Organization: Andreas Ney (Universität Duisburg-Essen)

MA 57.6: Vortrag

Donnerstag, 17. März 2011, 18:00–18:20, HSZ 403

Investigation of strain and doping induced ferromagnetism in LaCoO3 by x-ray absorption and magnetic circular dichroismMichael Merz1, Peter Nagel1, Andrea Assmann1,2, Stephan Uebe1,2, Markus Wissinger1,2, Hilbert von Löhneysen1,3, Dirk Fuchs1, and •Stefan Schuppler11Institut für Festkörperphysik, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany — 2Fakultät für Physik, Karlsruhe Institute of Technology — 3Physikalisches Institut, Karlsruhe Institute of Technology, 76031 Karlsruhe, Germany

Undoped bulk LaCoO3 remains paramagnetic down to liquid He temperatures; it has been shown that upon cooling, the Co3+ ions undergo a spin-state transition to the S=0 low-spin (LS) state. We explore two avenues for inducing ferromagnetism in this compound: (i) strain, applied by the lattice mismatch between a LaCoO3 thin film and the substrate, and (ii) doping, both with electrons and holes. The spin-state structure of these systems can be studied in detail by near-edge x-ray absorption fine structure and by soft x-ray magnetic circular dichroism at the Co L2,3 and the O K edges. It turns out that the mechanism responsible for ferromagnetism in each of the systems – strained undoped, electron doped, hole doped – is unique and distinctly different from the others, explaining the vastly differing transition temperatures. In all cases, a mix of Co spin states is realized, and thus their actual microscopic arrangement is a co-determining factor for magnetic parameters like the spin and orbital moments.

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