2.0

1. 2.0 55 mK 700 mK 10 K 1.0 0.0 -1.0 0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 |Q| (Å-1) The origin of persistent spin dynamics and residual entropy in the stuffed spin ice Ho2.3Ti1.7O7− PI: H. D. Zhou, National High Magnetic Field Laboratory, Florida State University, NCNR/NIST, Oak Ridge National Lab, University of Maryland, Indiana University, Institut Laue-Langevin NSF Award Numbers: DMR-0084173, DMR -0454672. Nature tends to find ordered ground states of systems as the thermal energy is removed, and the free energy is minimized through a phase transition. Such a process involves competing entropy terms (which become weaker as the temperature is lowered) and internal energy terms (which lead to the formation of bonds or ordered states) that determine which phases of matter are stable. The so-called “spin ices” form when exchange interactions, crystal fields, and dipolar interactions are in a delicate balance. This gives rise to a ground state which has a considerable amount of residual spin entropy, much like the proton entropy in water ice through the freezing transition. Recently, stuffed spin-ices have provided a means to probe how delicate of a balance is needed to stabilize the disordered ground state. Surprisingly, it is found that an increase of the density of spins results in very little change in the residual entropy, which Elastic neutron scattering pattern of Ho2.3Ti1.7O7− at 1.5 K (typical of spin ice) leads to the interesting idea that residual entropy states might be more common than once believed for magnetism. We prepared the single crystal of stuffed spin ice Ho2.3Ti1.7O7−, and completed the first set of neutron scattering experiments which shows even with this large perturbation, the system still has some key signatures of the spin-ice state, but the spin dynamics is significantly altered. H. D. Zhou et al., J. Phys.:Condens. Matter 19, 342201 (2007) Inelastic neutron scattering patterns of Ho2.3Ti1.7O7−, indicating a dynamic ground state