Gapless spin liquid ground state in the S=1/2 vanadium oxyfluoride kagome antiferromagnet [NH4]2[C7H14N][V7O6F18]

TL;DR

This study demonstrates that the vanadium oxyfluoride DQVOF exhibits a gapless spin liquid ground state, with no spin freezing observed down to 40 mK, making it a promising model for S=1/2 kagome physics.

Contribution

It provides experimental evidence of a gapless spin liquid in a S=1/2 kagome antiferromagnet with weakly coupled interlayer spins.

Findings

No spin freezing down to 40 mK

Weak coupling of S=1 spins to kagome layers

Displays a gapless spin liquid ground state

Abstract

The vanadium oxyfluoride [NH4]2[C7H14N][V7O6F18] (DQVOF) is a geometrically frustrated magnetic bilayer material. The structure consists of S=1/2 kagome planes of V4+ d1 ions with S=1 V3+ d2 ions located between the kagome layers. Muon spin relaxation measurements demonstrate the absence of spin freezing down to 40 mK despite an energy scale of 60 K for antiferromagnetic exchange interactions. From magnetization and heat capacity measurements we conclude that the S=1 spins of the interplane V3+ ions are weakly coupled to the kagome layers, such that DQVOF can be viewed as an experimental model for S=1/2 kagome physics, and that it displays a gapless spin liquid ground state.