Dzyaloshinsky-Moriya interaction in vesignieite: A route to freezing in a quantum kagome antiferromagnet

TL;DR

This study uses electron spin resonance to show that in-plane Dzyaloshinsky-Moriya interactions in vesignieite suppress quantum spin fluctuations, leading to magnetic ordering instead of a spin-liquid state, and highlights lattice effects and inhomogeneity.

Contribution

It reveals the dominant in-plane Dzyaloshinsky-Moriya anisotropy in vesignieite and its role in promoting magnetic order over a quantum spin-liquid state.

Findings

In-plane Dzyaloshinsky-Moriya anisotropy dominates the spin interactions.

Suppression of quantum spin fluctuations promotes long-range magnetic order.

Evidence of lattice instability and local inhomogeneity affecting magnetic properties.

Abstract

We report an electron spin resonance investigation of the geometrically frustrated spin-1/2 kagome antiferromagnet vesignieite, BaCu$_3$V$_2$O$_8$(OH)$_2$. Analysis of the line widths and line shifts indicates the dominance of in-plane Dzyaloshinsky-Moriya anisotropy that is proposed to suppress strongly quantum spin fluctuations and thus to promote long-range ordering rather than a spin-liquid state. We also evidence an enhanced spin-phonon contribution that might originate from a lattice instability and discuss the origin of a low-temperature mismatch between intrinsic and bulk susceptibility in terms of local inhomogeneity.