Crystal field levels in scandium-doped spin ice

We have determined the defect structure of scandium-doped holmium titanate using diffuse neutron scattering, and we find evidence for charge-compensating oxygen vacancies on so-called O(1) sites. According to crystal electric field (CEF) calculations using a point charge model, an O(1) vacancy is expected to lead to the four neighbouring holmium ions adopting a non-magnetic singlet ground state. We now propose to test our theoretical predictions of the CEF energy levels of scandium-doped holmium titanate using inelastic neutron scattering on MARI. Determination of the CEF energy level scheme will allow us to understand the effects of doping on the single-ion magnetism, and to simulate the collective behaviour of this novel magnetic system.