Structural and magnetic properties of the Kagomé antiferromagnet YbBaCo4O7

✍ Scribed by A. Huq; J.F. Mitchell; H. Zheng; L.C. Chapon; P.G. Radaelli; K.S. Knight; P.W. Stephens

• Book ID: 104029491
• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 465 KB
• Volume: 179
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2006.01.010

✦ Synopsis

The mixed-valent compound YbBaCo 4 O 7 is built up of Kagome´sheets of CoO 4 tetrahedra, linked in the third dimension by a triangular layer of CoO 4 tetrahedra in an analogous fashion to that found in the known geometrically frustrated magnets such as pyrochlores and SrCr 9x Ga 12À9x O 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 4 O 7 undergoes a first-order trigonalorthorhombic phase transition at 175 K. We show that this transition occurs as a response to a markedly underbonded Ba 2+ site in the high-temperature phase and does not appear to involve charge ordering of Co 2+ /Co 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.