ATTENTION !!! SEMINAIRE ANNULE !!! Quantum spins on a hyperkagome lattice : a neutron scattering study with a view to future neutron scattering possibilities at the European Spallation Source

Orateur : Pascale P. DEEN (ESS, Lund and Niels Bohr Institute, Copenhagen)

The 2D antiferromagnetic Heisenberg model on the kagome lattice is th e archetypal frustrated system and remains highly studied. However, in recent years, 3D pyrochlore or garnet lattices with significant anisotropy have shown emergent states of matter such as monopole excitations in spin ice materials and long range multipolar director states in Gd3Ga5O12 (GGG). These phenomena reveal that the combination of a 3 dimensional crystal structure and magnetic frustration are powerful indicators of exotic states of matter. We have recently studied the magnetic behaviour of the magnetic correlation and low lying spin waves in single crystal Yb3Ga5O12 (YbGG), isostructural to GGG, in the short ranged ordered director state. In YbGG the director state is subtly different to the GGG counterpart and is particularly interesting since Yb3+ ions present an effective S = 1/2 moment thus enabling quantum effects. I shall first present some recent results on the magnetic behaviour of rare earth ions on hyperkagome lattices. These results illuminate the importance of neutron scattering in the study of magnetic states of matter. The European Spallation Source, funded in part by France, is under construction in Lund, Sweden, and shall provide novel neutron scattering instrumentation with enhanced fluxes. I shall, second, provide a brief overview of the ESS neutron scattering instrument suite that will be hugely beneficial to the scientific communities focussed on materials research.

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