### Session H8: Focus Session: Frustrated Magnetism - Kagome I

8:00 AM–11:00 AM, Tuesday, February 28, 2012
Room: 208

Chair: Peter Schiffer, Pennsylvania State University

Abstract ID: BAPS.2012.MAR.H8.2

### Abstract: H8.00002 : NMR study of the spin-1/2 near-kagome system Vesignieite

8:36 AM–8:48 AM

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#### Authors:

Jeffrey Quilliam
(Laboratoire de Physique des Solides, Universite Paris-Sud)

Fabrice Bert
(Laboratoire de Physique des Solides, Universite Paris-Sud)

Ross Colman
(Department of Chemistry, University College London)

David Boldrin
(Department of Chemistry, University College London)

Andrew Wills
(Department of Chemistry, University College London)

Philippe Mendels
(Laboratoire de Physique des Solides, Universite Paris-Sud)

The spin-1/2 kagome lattice antiferromagnet is understood to be an ideal setting in which to find novel quantum spin liquid physics. Here, $^{51}$V NMR results are presented on the quantum spin system Vesignieite, which closely approximates such an antiferromagnetic kagome model, possessing a minute 0.7\% length difference between inequivalent Cu-Cu bonds. We obtain a measure of the intrinsic magnetic susceptibility of the near-kagome lattice, which shows commonalities with other kagome systems, in particular Herbertsmithite. Meanwhile, the system is found to undergo partial spin freezing at a surprisingly high temperature of $T_C = 9 K \simeq J/6$. Through a loss of NMR intensity and detailed analysis of the spectral linewidth, we infer a heterogeneous ground state in which 50\% of the spins are very weakly frozen, with a moment of $\sim 0.2$ $\mu_B$ and the remaining 50\% remain dynamic down to very low temperatures. These results are found to be highly consistent with $\mu$SR studies, which find a similar frozen fraction and small size of magnetic moment. We propose that the elevated transition temperature and weakly frozen ground state are explained by the Dzyaloshinskii-Moriya interaction and a proximity to the resulting quantum phase transition.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.H8.2