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Structural Phase Transition in the S = 1/2 Kagome System Cs2ZrCu3F12 and a Comparison to the Valence-Bond-Solid Phase in Rb2SnCu3F12

DOI: 10.1021/cm201762f DOI Help

Authors: Sandra A. Reisinger (School of Chemistry and EaStChem, University of St. Andrews) , Chiu C. Tang (Diamond Light Source) , Stephen P. Thompson (Diamond Light Source) , Finlay D. Morrison (School of Chemistry and EaStChem, University of St. Andrews) , Philip Lightfoot (School of Chemistry and EaStChem, University of St. Andrews)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials , VOL 23 (18)

State: Published (Approved)
Published: September 2011

Abstract: The crystal structure of the S = 1/2 kagome system Cs2ZrCu3F12 has been determined at both 295 and 125 K via single-crystal X-ray diffraction. A first-order structural phase transition is seen near 225 K, confirmed by variable-temperature synchrotron powder diffraction studies, in which the structure transforms from rhombohedral (Rm) to monoclinic (P21/m). A corresponding abrupt change in dielectric constant is observed near the same temperature. The phase transition is driven by a dramatic change in coordination around the Zr site, which changes from regular octahedral in the rhombohedral phase to a seven-coordinate environment in the monoclinic phase. This leads to a severe buckling of the copper fluoride kagome layers and significant changes in the geometry around the Cu sites, which correlates with both the observed dielectric anomaly and a previously observed anomaly in magnetic susceptibility. It is suggested that this structural phase transition ultimately permits long-range antiferromagnetic ordering in Cs2ZrCu3F12, contrasting markedly with the behavior of the analogue Rb2SnCu3F12, which exhibits a “pinwheel” valence-bond-solid ground state.

Subject Areas: Chemistry

Instruments: I11-High Resolution Powder Diffraction

Added On: 09/09/2011 08:45

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