Slow and static spin correlations in Dy_2+xTi_2-xO _7-δ

The static and dynamic spin correlations in the spin ices Dy _2.3Ti_1.7O_6.85 and Dy₂Ti ₂O₇ have been studied in polarized neutron diffraction and neutron spin echo experiments. The measurements reveal that, below 100mK, the magnetic scattering broadens and shifts to higher |Q| upon stuffing the pyrochlore lattice with additional Dy³⁺ ions. These observations can be related, by means of reverse Monte Carlo simulation, to the modified distribution of near-neighbour distances and an overall more antiferromagnetic character of the near-neighbour couplings. The dynamic measurements show that the spin correlations are slower in the stuffed system. These results will be discussed and compared to the holmium analogues.