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Title: Structural and Magnetic Properties of the Kagome Antiferromagnet YbBaCo4O7

Abstract

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.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914000
Report Number(s):
BNL-78568-2007-JA
Journal ID: ISSN 0022-4596; JSSCBI; TRN: US0801464
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Solid State Chem.; Journal Volume: 179; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; DIMENSIONS; MAGNETIC PROPERTIES; MAGNETS; NEUTRONS; SYMMETRY; SYNCHROTRONS; X-RAY DIFFRACTION; NSLS; national synchrotron light source

Citation Formats

Huq,A., Mitchell, J., Zheng, H., Chapon, L., Radaelli, P., Knight, K., and Stephens, P. Structural and Magnetic Properties of the Kagome Antiferromagnet YbBaCo4O7. United States: N. p., 2006. Web. doi:10.1016/j.jssc.2006.01.010.
Huq,A., Mitchell, J., Zheng, H., Chapon, L., Radaelli, P., Knight, K., & Stephens, P. Structural and Magnetic Properties of the Kagome Antiferromagnet YbBaCo4O7. United States. doi:10.1016/j.jssc.2006.01.010.
Huq,A., Mitchell, J., Zheng, H., Chapon, L., Radaelli, P., Knight, K., and Stephens, P. Sun . "Structural and Magnetic Properties of the Kagome Antiferromagnet YbBaCo4O7". United States. doi:10.1016/j.jssc.2006.01.010.
@article{osti_914000,
title = {Structural and Magnetic Properties of the Kagome Antiferromagnet YbBaCo4O7},
author = {Huq,A. and Mitchell, J. and Zheng, H. and Chapon, L. and Radaelli, P. and Knight, K. and Stephens, P.},
abstractNote = {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.},
doi = {10.1016/j.jssc.2006.01.010},
journal = {J. Solid State Chem.},
number = 4,
volume = 179,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The mixed-valent compound YbBaCo{sub 4}O{sub 7} is built up of Kagome 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 9} {sub x} Ga{sub 12-9} {sub x} 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{sup {yields}}orthorhombic phase transition at 175 K. We show that this transition occurs asmore » 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.« less
  • The first-order structural phase transition at T{sub S}{approx}240K in the extended kagome antiferromagnet TmBaCo{sub 4}O{sub 7} has been studied by neutron powder diffraction. In order to comprehend the microscopic origin of the transition, a detailed symmetry analysis is performed, based on crystallographic parameters obtained by Rietveld analysis of the neutron data. The results are consistent with the P31c {yields} Pna2{sub 1} symmetry lowering and support a displacive nature of the phase transition. The complex tilting pattern of CoO{sub 4} tetrahedra in both triangular and kagome sublattices is described based on symmetry-adapted pseudovector distortion modes of the parent P6{sub 3}mc hexagonalmore » structure. Our analysis reveals that the unusual topology of the crystal structure does not allow CoO{sub 4} tetrahedra to rotate as rigid units, resulting in their inevitable distortions, whatever the combination of rotational modes considered. A possible analogy between polyhedral distortions and spin frustration in this system is discussed.« less
  • Cited by 4
  • We propose a general nonperturbative scheme that quantitatively maps the low-energy sector of spin-1/2 frustrated Heisenberg antiferromagnets to effective generalized quantum dimer models. We develop the formal lattice-independent frame and establish some important results on (i) the locality of the generated Hamiltonians, (ii) how full resummations can be performed in this renormalization scheme. The method is then applied to the much debated kagome antiferromagnet for which a fully resummed effective Hamiltonian - shown to capture the essential properties and provide deep insights on the microscopic model [D. Poilblanc, M. Mambrini, and D. Schwandt, Phys. Rev. B 81, 180402(R) (2010)] -more » is derived.« less