Magnetism manifests itself in a variety of forms in crystalline solids, and our understanding of it often relies on lattice spin models. In this talk, I will describe a few case studies where neutron scattering helps to establish the correct model and reveal the associated characteristics. I will begin with an ionic case, where a lattice of spin 1/2 on Cu(2+) exhibits highly classical excitations that have non-trivial topological structure in their eigen functions. Then I will describe a seemingly classical case of high-spin Co(2+), where spin-orbit interactions actually make the system behave in a highly quantum fashion, especially in the context of the Kitaev honeycomb model. Finally, I will introduce a generic scenario where the construction of lattice spin models based on an ionic picture may be misleading, and show how inelastic neutron scattering may help us find a suitable model.
Dr. Christian Franz
Dr. Jitae Park