Ground state and intrinsic susceptibility of the kagome antiferromagnet vesignieite as seen by51V NMR

The intrinsic magnetic susceptibility and local magnetization of the near-kagome quantum magnet vesignieite, Cu 3 BaV 2 O 8 (OH) 2 , are presented as measured using 51 V NMR. The NMR line shift gives an accurate measurement of the intrinsic susceptibility of the kagome sites which closely resembles that of the quantum spin liquid herbertsmithite [A. Olariu et al., Phys. Rev. Lett. 100, 087202 (2008)]. It is therefore surprising that, at T C ≃ 9 K, a transition to a heterogeneous ground state is observed. A gradual wipeout of half the NMR intensity indicates a slowly fluctuating spin liquid component, and a detailed analysis of the linewidth reveals the onset of static magnetism at the remaining half of the sites. It is proposed that this transition and unusual ground state originate from a nearby quantum critical point induced by the Dzyaloshinskii-Moriya interaction