Magnetic Structure Solution of Frustrated Spin Systems

Magnetic Structure Solution of Frustrated Spin Systems

In frustrated magnetic materials, geometry and magnetic interactions combine to suppress conventional magnetic order. Instead, disordered "spin liquid" states can host exotic magnetic phenomena which persist to the lowest measurable temperatures. Neutron scattering is an ideal experimental technique to understand spin-liquid states, but the absence of conventional magnetic order means that standard data-analysis methods cannot be used. Two limitations have traditionally restricted our understanding spin liquids at the atomic scale: (i) the magnetic interactions must be anticipated, and (ii) single-crystal samples must be available.

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Date

February 12, 2015 - 9:00am

Location

Howey N110

In frustrated magnetic materials, geometry and magnetic interactions combine to suppress conventional magnetic order. Instead, disordered "spin liquid" states can host exotic magnetic phenomena which persist to the lowest measurable temperatures. Neutron scattering is an ideal experimental technique to understand spin-liquid states, but the absence of conventional magnetic order means that standard data-analysis methods cannot be used. Two limitations have traditionally restricted our understanding spin liquids at the atomic scale: (i) the magnetic interactions must be anticipated, and (ii) single-crystal samples must be available.

In my presentation, I will show how neutron-scattering data can be converted robustly into a three-dimensional model of the spin-liquid state. Using an atomistic refinement approach, I show that it is possible to recover accurate three-dimensional information from powder-averaged data, without making any assumptions about the underlying magnetic interactions. I will present experimental results for two materials. First, I present evidence for a "hidden order" state in the canonical frustrated magnet Gd3Ga5O12. Second, I use single-crystal neutron-scattering data to understand the origin of magnetic disorder in beta-Mn and its alloys. Finally, I will discuss the implications of these results for understanding disorder in other materials.