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Title: Approaching the Ground State of the Kagome Antiferromagnet

Abstract

Y{sub 0.5}Ca{sub 0.5}BaCo{sub 4}O{sub 7} contains kagome layers of Co ions, whose spins are strongly coupled, with a Curie-Weiss temperature of -2200 K. At low temperature, T=1.2 K, our diffuse neutron scattering study with polarization analysis reveals characteristic spin correlations close to a predicted two-dimensional coplanar ground state with staggered chirality. The absence of three-dimensional long-range antiferromagnetic order indicates negligible coupling between the kagome layers. The scattering intensities are consistent with high spin S=3/2 states of Co{sup 2+} in the kagome layers and low spin S=0 states for Co{sup 3+} ions on interlayer sites. Our observations agree with previous Monte Carlo simulations indicating a ground state of effectively short range, staggered chiral spin order.

Authors:
 [1]; ;  [2]
  1. Institut fuer Festkoerperforschung, Forschungszentrum Juelich, D-52425 Juelich (Germany)
  2. Physik der Kondensierten Materie, TU-Braunschweig, D-38106 Braunschweig (Germany)
Publication Date:
OSTI Identifier:
20955453
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevLett.98.067201; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 36 MATERIALS SCIENCE; ANTIFERROMAGNETISM; BARIUM COMPOUNDS; CALCIUM COMPOUNDS; CHIRALITY; COBALT IONS; COBALT OXIDES; COMPUTERIZED SIMULATION; CURIE-WEISS LAW; GROUND STATES; LAYERS; MONTE CARLO METHOD; NEUTRON DIFFRACTION; POLARIZATION; SPIN; TEMPERATURE RANGE 0000-0013 K; THREE-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL CALCULATIONS; YTTRIUM COMPOUNDS

Citation Formats

Schweika, W., Valldor, M., and Lemmens, P. Approaching the Ground State of the Kagome Antiferromagnet. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.067201.
Schweika, W., Valldor, M., & Lemmens, P. Approaching the Ground State of the Kagome Antiferromagnet. United States. doi:10.1103/PHYSREVLETT.98.067201.
Schweika, W., Valldor, M., and Lemmens, P. Fri . "Approaching the Ground State of the Kagome Antiferromagnet". United States. doi:10.1103/PHYSREVLETT.98.067201.
@article{osti_20955453,
title = {Approaching the Ground State of the Kagome Antiferromagnet},
author = {Schweika, W. and Valldor, M. and Lemmens, P.},
abstractNote = {Y{sub 0.5}Ca{sub 0.5}BaCo{sub 4}O{sub 7} contains kagome layers of Co ions, whose spins are strongly coupled, with a Curie-Weiss temperature of -2200 K. At low temperature, T=1.2 K, our diffuse neutron scattering study with polarization analysis reveals characteristic spin correlations close to a predicted two-dimensional coplanar ground state with staggered chirality. The absence of three-dimensional long-range antiferromagnetic order indicates negligible coupling between the kagome layers. The scattering intensities are consistent with high spin S=3/2 states of Co{sup 2+} in the kagome layers and low spin S=0 states for Co{sup 3+} ions on interlayer sites. Our observations agree with previous Monte Carlo simulations indicating a ground state of effectively short range, staggered chiral spin order.},
doi = {10.1103/PHYSREVLETT.98.067201},
journal = {Physical Review Letters},
number = 6,
volume = 98,
place = {United States},
year = {Fri Feb 09 00:00:00 EST 2007},
month = {Fri Feb 09 00:00:00 EST 2007}
}
  • The kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu3(OH)6Cl2], which is known to exhibit a spinon continuum in the spin excitation spectrum.We demonstrated that the intrinsic local spin susceptibility ckagome, deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction. Combined with the magnetic fieldmore » dependence of ckagome that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.« less
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  • Here, the kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu 3(OH) 6Cl 2], which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χkagome, deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction.more » Combined with the magnetic field dependence of χ kagome that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.« less
  • The coupled cluster method (CCM) is applied to a spin-half model at zero temperature which interpolates between a triangular lattice antiferromagnet (TAF) and a kagome{prime} lattice antiferromagnet (KAF). The strength of the bonds which connect kagome{prime} lattice sites is J, and the strength of the bonds which link the non-kagome{prime} lattice sites to the kagome{prime} lattice sites on an underlying triangular lattice is J{sup {prime}}. Our results are found to be highly converged, and our best estimate for the ground-state energy per spin for the spin-half KAF (J{sup {prime}}=0) is {minus}0.4252J. The amount of classical ordering on the kagome{prime} latticemore » sites is also considered, and it is seen that this parameter goes to zero for values of J{sup {prime}} very close to the KAF point. Further evidence is also presented for CCM critical points which reinforce the conjecture that there is a phase near to the KAF point which is very different to that near to the TAF point (J=J{sup {prime}}).« less