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Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 34: Correlated Electrons: Metal-Insulator Transition 2

TT 34.12: Talk

Thursday, February 28, 2008, 17:00–17:15, H 2053

X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6 — •Tobias Burnus1, Zhiwei Hu1, Júlio C. Cezar2, Seiji Niitaka3, Hua Wu1, Hidenori Takagi3,4, Chun Fu Chang1, Nicholas B. Brookes2, Ling-Yun Jang5, Keng S. Liang5, and L. Hao Tjeng11II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln — 2European Synchrotron Radiation Facility, Grenoble, France — 3RIKEN and CREST, Saitama, Japan — 4University of Tokyo, Japan — 5National Synchrotron Research Center, Hsinchu, Taiwan

The valence-state of the transition-metal ions in the chain-like compounds Ca3CoRhO6 and Ca3FeRhO6 is currently an issue under debate. Using numerical simulations and x-ray absorption spectroscopy at the Rh-L2,3, the Co-L2,3, and the Fe-L2,3 edges we reveal a Co2+/Rh4+ configuration in Ca3CoRhO6 and Fe3+/Rh3+ in Ca3FeRhO6. X-ray magnetic circular dichroism at the Co-L2,3 edge shows that the Co2+ ions carry a giant orbital moment of about 1.7µB. We attribute this to a d01d21 ground state for the high-spin Co 3d7 configuration in trigonal prismatic coordination. The intrachain-ferromagnetic coupling of two neighboring Co ions is mediated by a low-spin Rh4+ ion (S = 1/2) in between.

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