Absence of spin-ice state in the disordered fluorite Dy2Zr2O7

Neutron scattering, ac magnetic susceptibility, and specific-heat studies have been carried out on polycrystalline Dy2Zr2O7. Unlike the pyrochlore spin ice Dy2Ti2O7, Dy2Zr2O7 crystallizes into the fluorite structure and the magnetic Dy3+ moments randomly reside on the corner-sharing tetrahedral sublattice with nonmagnetic Zr ions. Antiferromagnetic spin correlations develop below 10 K but remain dynamic down to 40 mK, with a significant amount of magnetic susceptibility. These correlations extend over the length of two tetrahedra edges and grow to six nearest neighbors with the application of a 20-kOe magnetic field. Magnetic heat capacity revealed a correlation peak at 2 K, but no Pauling's residual entropy was observed. We propose that the disorder precludes the development of spin-ice correlations seen in the chemically ordered Dy2Ti2O7 compound, with fluctuating spins in a disordered, liquidlike state (albeit slow) which do not freeze into a canonical spin-glass state that one might intuitively expect.