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Structural and magnetic properties of the Kagomé antiferromagnet YbBaCo4O7 |
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| Authors: | A Huq H Zheng PG Radaelli PW Stephens |
| Institution: | a Intense Pulsed Neutron Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439, USA b Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439, USA c ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, Didcot, Oxfordshire, OX11 0QX, UK d Department of Physics and Astronomy, SUNY Stonybrook, NY 11794, USA |
| Abstract: | The mixed-valent compound YbBaCo4O7 is built up of Kagomé sheets of CoO4 tetrahedra, linked in the third dimension by a triangular layer of CoO4 tetrahedra in an analogous fashion to that found in the known geometrically frustrated magnets such as pyrochlores and SrCr9xGa12−9xO19 (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. YbBaCo4O7 undergoes a first-order trigonal→orthorhombic phase transition at 175 K. We show that this transition occurs as a response to a markedly underbonded Ba2+ site in the high-temperature phase and does not appear to involve charge ordering of Co2+/Co3+ 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. |
| Keywords: | Geometric frustration Cobaltite Charge-order Neutron diffraction Kagomé Mixed-valent |
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