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A6: Characterization

X-ray absorption spectroscopy study of rare-earth-doped CaMnO3-δ

Shih-Show Chen1, Chia-Jyi Liu2, Wei-Cheng Wang3, Mei-Huei Wu3, and Ching-Lin Chang3
1Dept of Information Tech, Taipei College of Maritime Technology, Tamsui 251, Taiwan, 2Dept of Physics, Nat'l Changhua Univ of Education, Changhua 500, Taiwan, 3Dept of Physics, Tamkang Univ, Tamsui 251 Taiwan

We report x-ray absorption near edge structure (XANES) studies on a series of Ca1-xRexMnO3+δ samples with Re = Sm, Eu, Gd, Dy; x = 0.02. XANES spectra at the O K-edge and Mn L2,3-edge were recorded. Our results indicate that the Mn4+ to Mn3+ ratio increases with dopings, due to the increased charge introduced by the rare-earth elements. Also observed is the strength of Mn 3d-O 2p hybridization increases considerably, due to the smaller ionic size of the rare earth dopants. The increase of the Mn4+ to Mn3+ ratio and Mn 3d-O 2p hybridization could be responsible for the decrease of resistivity and absolute value of thermopower.