Dynamic spin ice: Pr$_{2}$Sn$_{2}$O$_{7}$*

In this presentation, we report a new spin ice - Pr$_{2}$Sn$_{2}$O$_{7}$ - which appears to have enhanced residual entropy due to the dynamic nature of the spins. Neutron scattering experiments show that at 200 mK, there is a significant amount of magnetic diffuse scattering which can be fit to the dipolar spin ice model. However, these short-ranged ordered spins have a quasielastic response that is atypical of the canonical spin ices, and suggests that the ground state is dynamic (ie. composed of locally ordered 2-in, 2-out spin configurations that can tunnel between energetically equivalent orientations). We report this as an example of a \textit{dynamic} spin ice down to 200 mK.