We report x-ray absorption near edge structure (XANES) on bulk samples of Ca1−x Gd x MnO3+δ with x = 0, 0.02, and 0.05. The transport properties measurements indicate that both resistivity and the absolute value of thermopower decrease with increasing x. Meanwhile, the temperature dependence of resistivity changes from non-metallic CaMnO3−δ to metallic for samples of x = 0.02 and 0.05. XANES spectra at the O K-edge, Mn L 2,3-edge, and Ca L 2,3-edge indicate that Mn 3d–O 2p hybridization increases considerably, and unoccupied (3d–4s) states of Ca decrease with increasing substitution content. The increases of Mn 3d–O 2p hybridization might be responsible for the decrease of the resistivity and the absolute value of thermopower upon partial Gd substitution for Ca.
Journal of Electronic Materials 43(6), pp.2094-2098