Vesignieite: a $S = \frac{1}{2}$ kagome antiferromagnet with dominant third-neighbor exchange

TL;DR

This study reveals that deuterated vesignieite, a nearly distortion-free $S=1/2$ kagome antiferromagnet, exhibits magnetic order driven primarily by third-neighbor exchange interactions, confirmed through neutron scattering and spin-wave analysis.

Contribution

It demonstrates that a dominant third-neighbor exchange $J_3$ stabilizes magnetic order in vesignieite, highlighting the importance of longer-range interactions in kagome antiferromagnets.

Findings

Vesignieite orders magnetically at 9K with a multi-k coplanar structure.

The magnetic behavior is primarily governed by a $J_3$ exchange interaction.

The spin-wave spectrum aligns with a $J_3$-only model including slight anisotropy.

Abstract

The spin-$\frac{1}{2}$ kagome antiferromagnet is an archetypal frustrated system predicted to host a variety of exotic magnetic states. We show using neutron scattering measurements that deuterated vesignieite BaCu$_{3}$V$_{2}$O$_{8}$(OD)$_{2}$, a fully stoichiometric $S=1/2$ kagome magnet with $<$1% lattice distortion, orders magnetically at $T_{\mathrm{N}}=9$K into a multi-k coplanar variant of the predicted triple-k octahedral structure. We find this structure is stabilized by a dominant antiferromagnetic 3$^{\mathrm{rd}}$-neighbor exchange $J_3$ with minor 1$^{\mathrm{st}}$- or 2$^{\mathrm{nd}}$--neighbour exchange. The spin-wave spectrum is well described by a $J_3$-only model including a tiny symmetric exchange anisotropy.