Neutron scattering and crystal field studies of the rare earth double perovskite Ba₂ErSbO₆

The rare earth double perovskite Ba₂ErSbO₆ contains an ordered face-centred cubic lattice of Er³⁺ ions, suggesting that this material is a candidate for showing the effects of geometric magnetic frustration. Crystal field effects have also been shown to be important in this series. We report a systematic experimental study involving neutron scattering and bulk measurements that show no evidence of long ranged magnetic order or spin glass freezing down to 70mK. A description of the system in terms of a crystal field scheme is established from inelastic neutron scattering. These measurements rule out significant magnetic coupling and show that all observed properties are fully explained by a model of uncoupled magnetic Er³⁺ ions.