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Ferrimagnetism in manganese-rich gallium and aluminium spinels due to mixed valence Mn2+-Mn3+ states

Bekheet, Maged F. and Schlicker, Lukas and Doran, Andrew and Siemensmeyer, Konrad and Gurlo, Aleksander (2018):
Ferrimagnetism in manganese-rich gallium and aluminium spinels due to mixed valence Mn2+-Mn3+ states.
In: Dalton Transactions, Royal Soc. Chemistry RSC, Cambridge, England, pp. 2727-2738, 47, (8), ISSN 1477-9226,
DOI: 10.1039/c7dt04765g,
[Online-Edition: http://pubs.rsc.org/en/Content/ArticleLanding/2018/DT/C7DT04...],
[Article]

Abstract

Stoichiometric (MnGa2O4 and MnAl2O4) and Mn-rich (Mn1.3Ga1.7O4 and Mn1.4Al1.6O4) spinels with a small inversion degree (0.14-0.21) were obtained via a co-precipitation route followed by calcination of the as-synthesized coprecipitates at 700-1000 degrees C under different gas atmospheres (air, N-2 or argon). In situ synchrotron XRD at elevated temperatures reveals the conditions for synthesizing phase-pure materials. The stoichiometry of the samples is confirmed by inductively coupled plasma optical emission spectrometry as well as by structure refinement of neutron diffraction data of phase-pure specimens. XANES characterization reveals the average oxidation state of manganese to be +2.2 and 2.3 in Mn1.3Ga1.7O4 and Mn1.4Al1.6O4 spinels, respectively. The mixed Mn2+-Mn3+ valence states are responsible for the ferrimagnetic properties of Mn1.3Ga1.7O4 and Mn1.4Al1.6O4 samples below 48 and 55 K, respectively, as well as for a smaller optical bandgap when compared to stoichiometric spinels.

Item Type: Article
Erschienen: 2018
Creators: Bekheet, Maged F. and Schlicker, Lukas and Doran, Andrew and Siemensmeyer, Konrad and Gurlo, Aleksander
Title: Ferrimagnetism in manganese-rich gallium and aluminium spinels due to mixed valence Mn2+-Mn3+ states
Language: English
Abstract:

Stoichiometric (MnGa2O4 and MnAl2O4) and Mn-rich (Mn1.3Ga1.7O4 and Mn1.4Al1.6O4) spinels with a small inversion degree (0.14-0.21) were obtained via a co-precipitation route followed by calcination of the as-synthesized coprecipitates at 700-1000 degrees C under different gas atmospheres (air, N-2 or argon). In situ synchrotron XRD at elevated temperatures reveals the conditions for synthesizing phase-pure materials. The stoichiometry of the samples is confirmed by inductively coupled plasma optical emission spectrometry as well as by structure refinement of neutron diffraction data of phase-pure specimens. XANES characterization reveals the average oxidation state of manganese to be +2.2 and 2.3 in Mn1.3Ga1.7O4 and Mn1.4Al1.6O4 spinels, respectively. The mixed Mn2+-Mn3+ valence states are responsible for the ferrimagnetic properties of Mn1.3Ga1.7O4 and Mn1.4Al1.6O4 samples below 48 and 55 K, respectively, as well as for a smaller optical bandgap when compared to stoichiometric spinels.

Journal or Publication Title: Dalton Transactions
Volume: 47
Number: 8
Publisher: Royal Soc. Chemistry RSC, Cambridge, England
Uncontrolled Keywords: X-RAY-ABSORPTION; MAGNETIC-PROPERTIES; MNIN2O4 SPINEL; PHASE-DIAGRAM; K-EDGE; MNGA2O4; MN; XANES; CO; STABILITY
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
Date Deposited: 22 Aug 2018 14:18
DOI: 10.1039/c7dt04765g
Official URL: http://pubs.rsc.org/en/Content/ArticleLanding/2018/DT/C7DT04...
Funders: German Research Foundation DFG: GU992/8-1, Office of Science,Office of Basic Energy Sciences, of the U.S. Department of Energy: DE-AC02-05CH11231, ALS
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