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Structure and Magnetism in the Kagome Antiferromagnet RBaCo4O7

Published online by Cambridge University Press:  26 February 2011

John F. Mitchell ,
Hong Zheng ,
Ashfia Huq ,
Laurent C. Chapon ,
Paolo G. Radaelli  and
Peter W. Stephens
John F. Mitchell
Affiliation:
mitchell@anl.gov, Argonne National Laboratory, Materials Science Division, MSD 223, 9700 S. Cass Avenue, Argonne, IL, 60439, United States, 630-252-5852, 630-252-7777
Hong Zheng
Affiliation:
zheng@anl.gov, Argonne National Laboratory, Materials Science Division, MSD 223, 9700 S. Cass Ave., Argonne, IL, 60439, United States
Ashfia Huq
Affiliation:
ahuq@ornl.gov, Oak Ridge National Laboratory, Spallation Neutron Source, Oak Ridge, TN, 37831, United States
Laurent C. Chapon
Affiliation:
l.c.chapon@rl.ac.uk, Rutherford Laboratory, ISIS Facility, Chilton, Didcot, OX11 0QX, United Kingdom
Paolo G. Radaelli
Affiliation:
p.g.radaelli@rl.ac.uk, Rutherford Laboratory, ISIS Facility, Chilton, Didcot, OX11 0QX, United Kingdom
Peter W. Stephens
Affiliation:
pstephens@notes.cc.sunysb.edu, SUNY Stonybrook, Physics and Astronomy, Stonybrook, NY, 11794, United States
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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

Keywords

crystallographic structuremagnetic propertiesneutron scattering
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 988: Symposium QQ – Solid-State Chemistry of Inorganic Materials VI , 2006 , 0988-QQ07-04
Copyright
Copyright © Materials Research Society 2007

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