The magnetic groundstate of an experimental $S=1/2$ kagomé antiferromagnet

Abstract

We have carried out neutron powder-diffraction measurements on zinc paratacamite Zn${}_x$Cu${}_{4-x}$(OH)${}_6$Cl${}_2$ with $x=1$, and studied the heat capacity in fields of up to 9 T for $0.5\le x\le 1$. The $x=1$ phase has recently been shown to be an outstanding realisation of the $S=1/2$ kagomé antiferromagnet. A weak mixing of Cu${}^{2+}$/Zn${}^{2+}$ between the Cu and the Zn sites, corresponding to $\sim 9$% of all Cu${}^{2+}$ for $x=1$, is observed using neutron diffraction. This ``antisite disorder'' provides a consistent explanation of the field dependence of the heat capacity for $0.8\le x\le 1$. From comparison of the derived Cu${}^{2+}$ occupancy of the Zn sites for $x=\mathrm{0.8...1}$ with the magnetic susceptibility, we argue that for $x=\mathrm{0.8...1}$ zinc paratacamite is a spin liquid without a spin gap. The presence of unpaired but nevertheless strongly interacting spins gives rise to a macroscopically degenerate ground state manifold, with increasingly glassy dynamics as $x$ is lowered.

Thorough revision of manuscript. Added 1 figure. Manuscript submitted to Physics Review Letters

References in corpus (7)

• Spin Dynamics of the Spin-1/2 Kagome Lattice Antiferromagnet ZnCu_3(OH)_6Cl_2
• Projected wavefunction study of Spin-1/2 Heisenberg model on the Kagome lattice
• Quantum magnetism in the paratacamite family: towards an ideal kagome lattice
• 17O NMR study of the intrinsic magnetic susceptibility and spin dynamics of the quantum kagome antiferromagnet ZnCu3(OH)6Cl2
• ^{63}Cu, ^{35}Cl, and ^{1}H NMR in the S=1/2 Kagomé Lattice ZnCu_{3}(OH)_{6}Cl_{2}
• Low temperature magnetization of the S=1/2 kagome antiferromagnet ZnCu_3(OH)_6Cl_2
• Quantum dimer model with Z_2 liquid ground-state: interpolation between cylinder and disk topologies and toy model for a topological quantum-bit

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• Modified kagome physics in the natural spin-1/2 kagome lattice systems - kapellasite Cu3Zn(OH)6Cl2 and haydeeite Cu3Mg(OH)6Cl2
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