Abstract: The Kitaev model is a highly frustrated magnetic Hamiltonian with a remarkable spin liquid ground state, whose excitations could support topologically protected quantum computation. The layered magnet α-RuCl3 has emerged as a leading candidate in the search for a realization of this model Hamiltonian. However, magnetism in RuCl3 is complicated by the presence of additional interactions which compete with the dominant Kitaev term. Candidate Hamiltonians proposed to describe this material typically include at least three leading terms, as well a variety of secondary interactions.

I will describe our characterization of the magnetic ground state by neutron and x-ray diffraction, and how these results have helped to narrow down the appropriate parameter regime to describe magnetism in RuCl3. Resonant elastic x-ray scattering results determining the magnetic moment direction have been particularly useful in placing unambiguous constraints on the sign and the magnitude of the various magnetic interactions. These results have helped lay the groundwork for our current understanding of the balance of magnetic interactions underlying the exotic phenomena observed in RuCl3.