Structural phase transitions in the kagome lattice based materials Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5)
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The solid solution Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5) has been investigated crystallographically between 100 and 300 K using synchrotron X-ray powder diffraction and, in the case of x = 0, neutron powder diffraction. For Cs2SnCu3F12 (x = 0), there is a structural transition from the previously reported room temperature rhombohedral symmetry (R[3 with combining macron]m) to monoclinic (P21/n) symmetry at 170 K. This transformation is repeated for the x = 0.5 composition, but with an increased transition temperature of 250 K. For x = 1.0 the monoclinic phase is found at 300 K, suggesting that the transition temperature is increased even further. For x = 1.5 a different behaviour, more akin to that previously reported forCs2SnCu3F12, is found: a single phase transition between rhombohedral symmetry (R[3 with combining macron]) and triclinic symmetry (P[1 with combining macron]) is found at 280 K. In agreement with previous single crystal studies, Cs2SnCu3F12 powder exhibits strong antiferromagnetic interactions (Θ ~ −268 K) and long-range magnetic order at TN ~ 19.3 K. The finite magnetic moment observed for T < TN might be explained by a Dzyaloshinskii–Moriya interaction, due to the lowering of symmetry from rhombohedral to monoclinic, which was not suggested in the earlier single crystal study.
Downie , L J , Black , C , Ardashnikova , E I , Tang , C C , Vasiliev , A N , Golovanov , A N , Berdonosov , P S , Dolgikh , V A & Lightfoot , P 2014 , ' Structural phase transitions in the kagome lattice based materials Cs 2-x Rb x SnCu 3 F 12 (x = 0, 0.5, 1.0, 1.5) ' CrystEngComm , vol 16 , no. 32 , pp. 7419-7425 . DOI: 10.1039/C4CE00788C
© Royal Society of Chemistry 2014. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at http://dx.doi.org/10.1039/C4CE00788C
The collaboration between the University of St Andrews and Moscow State University was funded by a Royal Society International Exchanges grant, in collaboration with the Russian Foundation for Basic Research (12-03-92604). LJD thanks the EPSRC for a PhD studentship via a Doctoral Training grant (EP/P505097/1). ANV acknowledges support of RFBR through grants 13-02-00174, 14-02-92002 and 14-02-92693. This work was supported in part from the Russian Ministry of Education and Science, Increased Competitiveness Program of NUST (No. K2-2014-036).
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