title: Approaching the ground state of the kagomé antiferromagnet.
abstract: Y0.5Ca0.5BaCo4O7 contains kagomé 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 kagomé layers. The scattering intensities are consistent with high spin S=3/2 states of Co2+ in the kagomé layers and low spin S=0 states for Co3+ 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.affiliation: Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Schweika
authors.forename: M
authors.initials: M
authors.lastname: Valldor
authors.forename: P
authors.initials: P
authors.lastname: Lemmens