Structural and Magnetic Properties of the Kagome Antiferromagnet YbBaCo4O7
The mixed-valent compound YbBaCo{sub 4}O{sub 7} is built up of Kagom{acute e} sheets of CoO{sub 4} tetrahedra, linked in the third dimension by a triangular layer of CoO{sub 4} tetrahedra in an analogous fashion to that found in the known geometrically frustrated magnets such as pyrochlores and SrCr{sub 9x}Ga{sub 12-9x}O{sub 19} (SCGO). We have undertaken a study of the structural and magnetic properties of this compound using combined high-resolution powder neutron and synchrotron X-ray diffraction. YbBaCo{sub 4}O{sub 7} undergoes a first-order trigonal{yields}orthorhombic phase transition at 175 K. We show that this transition occurs as a response to a markedly underbonded Ba{sup 2+} site in the high-temperature phase and does not appear to involve charge ordering of Co{sup 2+}/Co{sup 3+} ions in the tetrahedra. The symmetry lowering relieves the geometric frustration of the structure, and a long-range-ordered 3-D antiferromagnetic state develops below 80 K.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 914000
- Report Number(s):
- BNL-78568-2007-JA; JSSCBI; TRN: US0801464
- Journal Information:
- J. Solid State Chem., Vol. 179, Issue 4; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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