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 LaMn_0.5Co_0.5O₃ — •T. Burnus¹, Z. Hu¹, H. H. Hsieh², H.-J. Lin³, C.-T. Chen³, P. A. Joy⁴, and L. H. Tjeng¹ — ¹II. 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 LaMn_1−xCo_xO₃ 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-L_3,2 and Mn-L_3,2 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 ⟨ L_z⟩ of Co²⁺ is very sensitive to tetrahedral distortions of the CoO₆ octahedron. ⟨ L_z⟩ is close to 1 for the undistorted CoO₆ octahedron and becomes smaller or larger than 1 for elongated or compressed octrahedra, respectively.