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Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P164
Diffuse neutron scattering from a kagomé antiferromagnet
Martin Valldor 1 , Werner Schweika 2
1 IPKM, TU-Braunschweig, D-38106 Braunschweig, Germany – 2 Forschungszentrum
Jülich, D-52425 Jülich, Germany
A new type of magnetic metal oxides has recently been discovered, containing a net
of tetrahedrally coordinated Co. The transition metal sublattice forms perfect kagomé
type layers and the interlayer coupling situation is geometrically frustrated. In the
stoichiometry Y0.5Ca0.5BaCo4O7 [1], this frustration together with an unusual spin
state of the inter-layers Co causes the layers to magnetically decouple. Although susceptibility
measurements indicate strong antiferromagnetic coupling between spins, the
magnetic part neutron diffraction data, separated through polarization, shows no longrange
order down to 1.2 K [2]. The observed diffuse peak indicates an ordering tendency
towards a staggered chiral ground state, a spin structure of Heisenberg spins in layers
called � (3)x � (3). This coplanar spin structure exhibits degeneracy with local chiral
disorder even at very low temperatures. Studies of this complex magnetic state give
clues to unique spin ordering effects close to their ground state.
[1] M.Valldor cond-mat/0605063 (2006) [2] M.Valldor et al. submitted (2006)
Fig. 1: Co substructure forming
kagomé layers