Structural disorder and properties of the stuffed pyrochlore Ho2TiO5

We report a structural and thermodynamic study of the '' stuffed spin ice '' material Ho2TiO5 [i.e., Ho-2(Ti1.33Ho0.67)O-6.67], 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 Ho2TiO5 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.