Magnetothermal study of a Dy-stuffed spin ice: Dy2 (Dyx Ti2-x) O7-x/2

We have studied the thermodynamics of the stuffed spin ice material, Dy2 (Dyx Ti2-x) O7-x/2, in which additional Dy3+ replace Ti4+ in the pyrochlore Dy2 Ti2 O7. Heat capacity measurements indicate that these materials lose the spin ice zero point entropy for x≥0.3, sharply contrasting with results on the analogous Ho materials. A finite ac susceptibility is observed as T→0 in both the Ho and Dy materials with x=0.67, which suggests that spin fluctuations persist down to T∼0. We propose that both the entropy and susceptibility data may be explained as a result of domains of local pyrochlore type structural order in these materials.