Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 83: [MA] Focussed Session "X-ray absorption spectra - state of the art of theory and experiment" (jointly with DS, HL, MM, O)
O 83.6: 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 dichroism — Michael Merz1, Peter Nagel1, Andrea Assmann1,2, Stephan Uebe1,2, Markus Wissinger1,2, Hilbert von Löhneysen1,3, Dirk Fuchs1, and •Stefan Schuppler1 — 1Institut 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.