Diffuse scattering investigation of out-of-equilibrium states in spin ice

The spin ice material Dy2Ti2O7 is a frustrated material where the magnetic spins on a tetrahedra can only point into or out of the 111 crystallographic axis. Moreover, long range dipolar interactions competing with the local exchange means that 2 spins point into and 2 out of the 111 axis, and this state is degenerate, meaning there is a manifold of lowest energy states. Excitations out of this ground state make a 3 in, 1 out excitation which is shown to behave like a magnetic monopole. These monopoles are thermally created and we can control the density of the monopoles by controlling the cooling through a transition. We have developed a new technique to do this which we propose to use on the WISH instrument to study the microscopic evolution of the correlations as the monopole density is changed. We will also develop a new technique for non-equilibrium studies using neutron scattering.