Spin-ice behavior in Dy2 Sn2-x Sbx O7+x2 and Dy2 NbSc O7

We report the magnetic and thermal properties of Dy2 Sn2-x Sbx O7+x2 (x=0, 0.25, and 0.5) and of Dy2 NbSc O7. We find evidence for Ising-like single ion ground states in the Dy2 Sn2-x Sbx O7+x2 materials. Furthermore, these materials possess nearly the same zero-point entropy as the canonical spin ices Ho2 Ti2 O7 and Dy2 Ti2 O7. These results strongly suggest that the Dy2 Sn2-x Sbx O7+x2 materials studied have spin-ice states at low temperatures. We also observe a somewhat reduced zero-point entropy in Dy2 NbSc O7, which is possibly associated with a higher level of cation disorder. The icelike states in these materials, despite the cation disorder on the B sites of the pyrochlore lattice, provide evidence for the robust nature of spin-ice behavior in the presence of disorder.