Intra-layer Cation Ordering in a Brownmillerite Super- Structure: Synthesis, Crystal and Magnetic Structures of Ca2FeCoO5
- McMaster University
- University of Saskatchewan
- Canadian Neutron Beam Centre, National Research Council, Chalk River Laboratorie
- ORNL
The synthesis, crystal and magnetic structures and the bulk magnetic properties of Ca2FeCoO5, a brownmillerite type oxide, are presented. The crystal structure, solved and refined from single crystal x-ray and powder neutron diffraction data, is described in Pbcm with cell parameters, a = 5.3652(3) , b = 11.0995(5) , c = 14.7982(7) . Thus, one axis, b in this setting, is doubled in comparison with the standard brownmillerite structure description giving rise to two sets of octahedral and tetrahedral sites. Aided by the strong scattering contrast between Fe and Co for neutrons, a nearly perfect cation site ordering, unique to this compound, is observed in the tetrahedral layers (which may be implicated in the b-axis doubling). A lesser degree of cation site ordering occurs in the octahedral sites. As well, this material shows an unique arrangement of tetrahedral chains, and a new space group for the brownmillerite family. The magnetic structure is G-type antiferromagnetic, with preferred orientation of magnetic moments parallel to the c-axis between 3.8K to 100K. A spin re-orientation occurs in the range of 100K to 225K, above which and up to 510K the orientation of magnetic moments switches to along the a-axis. This spin re-orientation has not been seen for any brownmillerite material before. The neutron diffraction data indicate different site specific ordering temperatures at about 450(5)K and 520(5)K. The refined ordered moments at 3.8K are somewhat smaller than expected for Fe3+ and Co3+(high spin) but are similar to those found in Sr2FeCoO5. There is evidence for spin canting from isothermal magnetization data that shows well pronounced hysteresis and remnant magnetization at 5K and 200K.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1032467
- Journal Information:
- Chemistry of Materials, Vol. 22, Issue 21; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANTIFERROMAGNETISM
CATIONS
CALCIUM COMPOUNDS
COBALT OXIDES
CRYSTAL STRUCTURE
GRAIN ORIENTATION
HYSTERESIS
IRON COMPOUNDS
LAYERS
MAGNETIC MOMENTS
MAGNETIC PROPERTIES
MAGNETIZATION
NEUTRON DIFFRACTION
ORIENTATION
SCATTERING
SPACE GROUPS
SPIN
SYNTHESIS
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
X-RAY DIFFRACTION