Structural behavior of the kagome antiferromagnet TmBaCo{sub 4}O{sub 7} : neutron diffraction study and group-theoretical consideration.

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Phys. Rev. B

DOI:https://doi.org/10.1103/PhysRevB.80.144107· OSTI ID:967954

Khalyavin, D D; Chapon, L C; Radaelli, P G; Zheng, H; Mitchell, J F

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 hexagonal 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.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 967954
• Report Number(s): ANL/MSD/JA-65644
• Journal Information: Phys. Rev. B, Journal Name: Phys. Rev. B Journal Issue: 2009 Vol. 80; ISSN 1098-0121
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
CRYSTAL STRUCTURE
DIFFRACTION
NEUTRON DIFFRACTION
NEUTRONS
ORIGIN
SPIN
SYMMETRY
TOPOLOGY