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Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.96: Poster

Wednesday, March 29, 2006, 14:30–18:30, P1

Valence and spin state in Ca3FeRhO6 and Ca3CoRhO6 studied by XAS — •Zhiwei Hu1, Tobias Burnus1, Seiji Niitaka2, Chun-Fu Chang1, Hua Wu1, Júlio Criginski Ceszar3, Nicholas B. Brookes3, Ling-Yun Jang4, Hong-Ji Lin4, Hidenori Takagi2, Keng San Liang4, Chen Te Chen4, and Liu Hao Tjeng11II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln — 2Magnetic Material Laboratory, RIKEN (Institute of Physical and Chemical Research), Wako 351-0198, Japan — 3European Synchrotron Radiation Facility, BP 220, Grenoble 38043, France — 4National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan

The physical properties of triangular-lattice systems has been attracting much interest because the geometrical frustration produces novel types of phase transitions. The triangular lattice in Ca3CoRhO6 and Ca3FeRhO6 consist of one-dimensional chains with faced-sharing CoO6 and FeO6 trigonal prisms and of RhO6 octahedra. Neutron diffraction experiments indicate ferromagnetic Ising-spin chains in Ca3CoRhO6 and a three-dimensional antiferromagnetic transition at 12 K in CaFeRhO6. The valence and spin states in both compounds are a matter of controversy. The combined experimental and theoretical X-ray absorption spectroscopy (XAS) study at the Co-, Fe- and Ru-L2,3 edges presents unambiguously Co2+/Rh4+ and Fe3+/Rh4+ states in Ca3CoRhO6 and CaFeRhO6, respectively. The X-ray magnetic circular dichroism at the Co-L2,3 edge indicates a large orbital moment of Co2+ in Ca3CoRhO6.

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