Precise determination of the hyperfine parameters of europium in multifluorite perovskites by 151Eu Mössbauer spectroscopy
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© 1994 American Physical Society (APS). This is the accepted version of the following article: Lindén, J. & Lippmaa, M. & Miettinen, J. & Tittonen, I. & Katila, T. & Karppinen, Maarit & Niinistö, L. & Nara, A. & Yamauchi, H. 1994. Precise determination of the hyperfine parameters of europium in multifluorite perovskites by 151Eu Mössbauer spectroscopy. Physical Review B. Volume 49, Issue 21. 15280-15286. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.49.15280, which has been published in final form at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.15280.
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School of Chemical Technology |
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
1994
Department
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Language
en
Pages
15280-15286
Series
Physical Review B, Volume 49, Issue 21
Abstract
The hyperfine interactions at the europium lattice sites in samples of the homologous (Fe,Cu)Sr2(Eu,Ce)nCu2O4+2n+z (n=2,3) series were studied by Eu151 Mössbauer spectroscopy. The work was motivated by the search for new superconducting phases. This homologous series is based on the YBa2Cu3O7−δ (1:2:3) structure. The samples used in the Mössbauer measurements consisted of crystallites with random orientation and grain oriented crystallites. The texture of oriented samples was analyzed by x-ray diffraction. The complete quadrupole Hamiltonian of the 21.5-keV γ-transition of Eu151 was successfully applied in the analyses of all the Mössbauer spectra. In samples having n≤2 the europium atoms occupy a single lattice site, whereas the spectra of the n=3 samples exhibit hyperfine interactions of the two different europium sites. Analyzing the hyperfine parameters of the latter samples was made possible by simultaneous fitting of three spectra, corresponding to three different crystal orientations of the same specimen. This fitting scheme also enables more precise determination of the hyperfine parameters in the n=2 samples. In these samples an electric field gradient (EFG), with a large negative-valued main component (Vzz) parallel with the crystal c axis, was found. In the n=3 samples, the two EFG’s of the europium sites were found to have Vzz components of opposite signs. The negative Vzz value was attributed to the rare-earth site adjacent to the CuO layer. This site, found in all samples of the series, corresponds to the rare-earth site of the 1:2:3 system.Description
Keywords
Mössbauer spectroscopy, multifluorite perovskites, europium
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Citation
Lindén, J. & Lippmaa, M. & Miettinen, J. & Tittonen, I. & Katila, T. & Karppinen, Maarit & Niinistö, L. & Nara, A. & Yamauchi, H. 1994. Precise determination of the hyperfine parameters of europium in multifluorite perovskites by 151Eu Mössbauer spectroscopy. Physical Review B. Volume 49, Issue 21. 15280-15286. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.49.15280.
