Spin-state transition, magnetism and local crystal structure in Eu_{1-x}Ca_xCoO_{3-d}
| Autor: | Vasiliev, A. N., Vasilchikova, T. M., Volkova, O. S., Kamenev, A. A., Kaul, A. R., Kuzmova, T. G., Tsymbarenko, D. M., Lomachenko, K. A., Soldatov, A. V., Streltsov, S. V., Lin, J. -Y., Kao, C. N., Chen, J. M., Abdel-Hafiez, M., Wolter, A. U. B., Klingeler, R. |
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| Rok vydání: | 2012 |
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| Zdroj: | J. Phys. Soc. Jpn. 82, 044714 (2013) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.7566/JPSJ.82.044714 |
| Popis: | The doping series Eu1-xCaxCoO3-d provides a rather peculiar way to study the spin-state transition in cobalt-based complex oxides since partial substitution of Eu3+ ions by Ca2+ ions does not increase the mean valence state of cobalt but is accompanied by appearance of oxygen vacancies in the ratio d \sim x/2. In the parent compound EuCoO3, the low spin (LS)-high spin (HS) transition takes place at temperatures so high that the chemical decomposition prevents its direct observation. The substitution of Eu3+ for Ca2+ in this system shifts the LS-HS transition to lower temperatures. The energy gap associated with this transition in octahedrally-coordinated Co3+ ions changes from 1940 K in EuCoO3 to 1540 K in Eu0.9Ca0.1CoO2.95 and 1050 K in Eu0.8Ca0.2CoO2.9. Besides, each O2- vacancy reduces the local coordination of two neighboring Co3+ ions from octahedral to pyramidal thereby locally creating magnetically active sites which couple into dimers. These dimers at low temperatures form another gapped magnetic system with very different energy scale, D~3 K, on the background of intrinsically non-magnetic lattice of octahedrally-coordinated low-spin Co3+ ions. Comment: 15 pages |
| Databáze: | arXiv |
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