Novel phases in spin ice accessed via the application of pressure.

On general grounds the combination of neutron scattering techniques and high pressure are expected to be a particularly useful set of probes of frustrated magnets. Frustrated magnets typically feature macroscopically degenerate ground states with exotic excitations. The most prominent members of the spin-ice group are Ho2Ti2O7 (HTO) and Dy2Ti2O7 (DTO), in which magnetism arises from localised rare-earth ions with a strong crystal-field anisotropy. These exchange interactions lead to the exotic behaviours which, in the case of spin ice materials, includes residual entropy, magnetic monopoles and a Coulomb phase. Under applied pressure, spin-ice compounds on the pyrochlore lattice are predicted to display exotic magnetic behaviour that included an infinite-order multicritical transition between a Coulomb and an ordered magnetised state.