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Structure and Magnetism in the Kagome Antiferromagnet RBaCo4O7

  • John F. Mitchell (a1), Hong Zheng (a2), Ashfia Huq (a3), Laurent C. Chapon (a4), Paolo G. Radaelli (a5) and Peter W. Stephens (a6)...

Abstract

The mixed-valent compound RBaCo4O7 (R=Rare earth, Y), hereafter abbreviated as R-114, 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 the Y-114 and Yb-114 compound using combined high resolution powder neutron and synchrotron X-ray diffraction. Both compounds undergo a first order trigonal → orthorhombic phase transition that breaks the trigonal symmetry of the structure. We show from Bond Valence Sum arguments that this transition occurs as a response to a markedly underbonded Ba2+ site in the high-temperature phase. The symmetry-lowering transition relieves the geometric frustration of the structure, and a long-range ordered 3-D antiferromagnetic state develops at low temperature. The magnetic structure of the Y compound has been solved and shows a compromise between the well-known 120° structure of the Kagomé net and a collinear antiferromagnet in the third dimension

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Keywords

Structure and Magnetism in the Kagome Antiferromagnet RBaCo4O7

  • John F. Mitchell (a1), Hong Zheng (a2), Ashfia Huq (a3), Laurent C. Chapon (a4), Paolo G. Radaelli (a5) and Peter W. Stephens (a6)...

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