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Insight into the local magnetic environments and deuteron mobility in jarosite (AFe3(SO4)2(OD,OD2)6, A = K, Na, D3O) and hydronium alunite ((D3O)Al3(SO4)2(OD)6), from variable-temperature2H MAS NMR spectroscopy
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Nielsen, Ulla Gro, Heinmaa, Ivo, Samoson, Ago, Majzlan, Juraj and Grey, Clare P. (2011) Insight into the local magnetic environments and deuteron mobility in jarosite (AFe3(SO4)2(OD,OD2)6, A = K, Na, D3O) and hydronium alunite ((D3O)Al3(SO4)2(OD)6), from variable-temperature2H MAS NMR spectroscopy. Chemistry of Materials, Vol.23 (No.13). pp. 3176-3187. doi:10.1021/cm2003929 ISSN 0897-4756.
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Official URL: http://dx.doi.org/10.1021/cm2003929
Abstract
Detailed insight into the magnetic properties and mobility of the different deuteron species in jarosites (AFe(3)(SO(4))(2)(OD)(6), A = K, Na, D(3)O) is obtained from variable-temperature (2)H MAS NMR spectroscopy performed from 40 to 300 K. Fast MAS results in high-resolution spectra above the Neel transition temperature (i.e., in the paramagnetic regime). The (2)H NMR hyperfine shift (delta), measured as a function of temperature, is a very sensitive probe of the local magnetic environment. Two different magnetic environments are observed: (i) Fe(2)-OD groups and D(3)O(+) ions in stoichiometric regions of the sample. Here, the delta((2)H) values are proportional to the bulk susceptibility and follow a Curie-Weiss law above 150 K. (ii) Fe-OD(2) groups and D(2)O molecules located near the Fe(3+) vacancies in the structure. The Fe(3+) ions near these vacancies show strong local antiferromagnetic couplings even high above the Neel temperature (of ca. 65 K). The D(2)O and D(3)O(+) ions located on the jarosite A site can be distinguished in the (2)H NMR spectra due to the different temperature dependence of their isotropic shifts. Motion of the D(3)O(+) ions was followed by investigating the isostructural (diamagnetic) compound (D(3)O)Al(3)(SO(4))(2)(OD)(6) and an activation energy of 6.3(4) kJ/mol is determined for the D(3)O(+) motion. Our NMR results support theories that ascribe the spin glass behavior that is observed for (H(3)O)Fe(3)(SO(4))(2)(OD)(6) but not for the other cation substituted jarosites, to the disorder of the D(3)O(+) ions and/or a less distorted Fe coordination environment. No signs of proton transfer reactions from the D(3)O(+) ion to the framework are observed.
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Subjects: | Q Science > QC Physics | ||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
| Library of Congress Subject Headings (LCSH): | Jarosite, Paramagnetism, Spin glasses, Solid state physics, Nuclear magnetic resonance, Ferrous sulfate, Proton transfer reactions | ||||
| Journal or Publication Title: | Chemistry of Materials | ||||
| Publisher: | American Chemical Society | ||||
| ISSN: | 0897-4756 | ||||
| Official Date: | 12 July 2011 | ||||
| Dates: |
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| Volume: | Vol.23 | ||||
| Number: | No.13 | ||||
| Page Range: | pp. 3176-3187 | ||||
| DOI: | 10.1021/cm2003929 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Funder: | Danmarks Grundforskningsfond [Danish National Research Foundation], L'Oreal-UNESCO for Women in Science Fellowship, National Science Foundation (U.S.), Estonian Science Foundation (ESF) | ||||
| Grant number: | ANS-272-06-0058 (DG), CHE-0221934 (NSF), CHE-0714183 (NSF), ETF 8198 (ESF) |
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