Synthesis and characterization of the K{sub 2}NiF{sub 4} phases La{sub 1+x}Sr{sub 1-x}Co{sub 0.5}Fe{sub 0.5}O{sub 4-{delta}} (x=0, 0.2)
- School of Chemistry, University of Birmingham, Birmingham B15 2TT (United Kingdom)
The K{sub 2}NiF{sub 4} phases LaSrCo{sub 0.5}Fe{sub 0.5}O{sub 4} and La{sub 1.2}Sr{sub 0.8}Co{sub 0.5}Fe{sub 0.5}O{sub 4}, and their reduced forms LaSrCo{sub 0.5}Fe{sub 0.5}O{sub 3.75} and La{sub 1.2}Sr{sub 0.8}Co{sub 0.5}Fe{sub 0.5}O{sub 3.85}, have been successfully prepared by solid-state reactions, followed by reduction in 10% H{sub 2}/N{sub 2} in order to produce oxygen-deficient materials. All materials crystallize in a tetragonal K{sub 2}NiF{sub 4} structure (space group I4/mmm) with Co and Fe randomly distributed over the B-sites of the structure. Moessbauer spectra have confirmed the trivalent state of Fe in these materials. In the reduced materials, oxide ion vacancies are confined to the equatorial planes of the K{sub 2}NiF{sub 4} structure and the Co is present almost entirely as Co{sup 2+} ions; low-temperature neutron powder diffraction data reveal that these reduced phases are antiferromagnetically ordered with a tetragonal noncollinear arrangement of the moments. The Co{sup 3+} ions, present in stoichiometric LaSrCo{sub 0.5}Fe{sub 0.5}O{sub 4} and La{sub 1.2}Sr{sub 0.8}Co{sub 0.5}Fe{sub 0.5}O{sub 4}, inhibit magnetic order and are assumed to be in the low-spin state. - Graphical abstract: The reduced K{sub 2}NiF{sub 4} phases LaSrCo{sub 0.5}Fe{sub 0.5}O{sub 3.75} and La{sub 1.2}Sr{sub 0.8}Co{sub 0.5}Fe{sub 0.5}O{sub 3.85} accommodate disordered oxide ion vacancies confined to equatorial planes of the structure. Magnetic exchange results in AFM order at low temperature, which can be represented by a tetragonal noncollinear model for the moments. Co{sup 3+} ions, present in stoichiometric LaSrCo{sub 0.5}Fe{sub 0.5}O{sub 4} and La{sub 1.2}Sr{sub 0.8}Co{sub 0.5}Fe{sub 0.5}O{sub 4}, inhibit magnetic order and are assumed to be in the low-spin state.
- OSTI ID:
- 21212053
- Journal Information:
- Journal of Solid State Chemistry, Vol. 181, Issue 10; Other Information: DOI: 10.1016/j.jssc.2008.06.039; PII: S0022-4596(08)00338-1; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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