| Autor: |
Fujishiro, H., Naito, T., Takeda, D., Yoshida, N., Watanabe, T., Nitta, K., Hejtmanek, J., Knizek, K., Jirak, Z. |
| Rok vydání: |
2012 |
| Předmět: |
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| Zdroj: |
Phys. Rev. B 87, 155153 (2013) |
| Druh dokumentu: |
Working Paper |
| DOI: |
10.1103/PhysRevB.87.155153 |
| Popis: |
Temperature dependence of the X-ray absorption near-edge structure (XANES) spectra at the Pr $L_{3}$- and Tb $L_{3}$-edges was measured for the (Pr$_{1-y}$Tb$_{y})_{0.7}$Ca$_{0.3}$CoO$_{3}$ system, in which a metal-insulator (MI) and spin-state (SS) transition took place simultaneously at a critical temperature $T_{\rm MI}$. A small increase in the valence of the terbium ion was found below $T_{\rm MI}$, besides the enhancement of the praseodymium valence; the trivalent states, which are stable at room temperature, change to a 3+/4+ ionic mixture at low temperatures. In particular for the $y$=0.2 sample, the average valence determined at 8 K amounts to 3.03+ and 3.25+ for the Tb and Pr ion, respectively. In analogous (Pr$_{1-y}$RE$_{y})_{0.7}$Ca$_{0.3}$CoO$_{3}$ samples (RE=Sm and Eu), in which the MI-SS transition also took place, no valence shift of the RE ion was detected in the XANES spectra at the RE ion $L_{3}$-edge. The role of the substituted RE ion for the Pr-site on the MI-SS transition is discussed. |
| Databáze: |
arXiv |
| Externí odkaz: |
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