Structural disorder and properties of the stuffed pyrochlore Ho2 Ti O5

We report a structural and thermodynamic study of the "stuffed spin ice" material Ho2 Ti O5 [i.e., Ho2 (Ti1.33 Ho0.67) O6.67], comparing samples synthesized through two different routes. Neutron powder diffraction and electron diffraction reveal that the previously reported defect fluorite phase has short-range pyrochlore ordering, in that there are domains in which the Ho and Ho Ti sublattices are distinct. By contrast, a sample prepared through a floating zone method has long-range ordering of these sublattices. Despite the differences in crystal structures, the two versions of Ho2 Ti O5 display similar magnetic susceptibilities. Field dependent magnetization and measured recovered entropies, however, show a difference between the two forms, suggesting that the magnetic properties of the stuffed pyrochlores depend on the local structure.