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Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 26: Metal-Insulator Transition

TT 26.12: Talk

Thursday, March 29, 2007, 17:00–17:15, H19

X-ray magnetic circular dicroism study of LaMn0.5Co0.5O3 — •T. Burnus1, Z. Hu1, H. H. Hsieh2, H.-J. Lin3, C.-T. Chen3, P. A. Joy4, and L. H. Tjeng11II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln — 2Chung Cheng Institute of Technology, National Defense University, Taoyuan 335, Taiwan — 3National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan — 4Physical and Material Chemistry Division, National Chemical Laboratory, Pune 411008, India

The perovskite LaMn1−xCoxO3 system shows a multitude of magnetic properties, ranging from the diamagnetic LaCoO3 via ferromagnetism in the mixed region to the antiferromagnetic LaMnO3. For x = 0.5 soft-X-ray absorption spectroscopy at the Co-L3,2 and Mn-L3,2 edge reveals the divalent state for cobalt ions and the tetravalent for manganese ions. X-ray magnetic circular dichroic (XMCD) spectra indicate ferromagnetic coupling between Co2+ ions and Mn4+ ions. We found from the analysis of the XMCD spectra using configuration-interaction cluster calculations that the orbital moment ⟨ Lz⟩ of Co2+ is very sensitive to tetrahedral distortions of the CoO6 octahedron. ⟨ Lz⟩ is close to 1 for the undistorted CoO6 octahedron and becomes smaller or larger than 1 for elongated or compressed octrahedra, respectively.

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