Magnetothermal study of a Dy-stuffed spin ice: Dy 2 ( Dy x Ti 2 − x ) O 7 − x / 2

We have studied the thermodynamics of the stuffed spin ice material, ${\text{Dy}}_{2}({\text{Dy}}_{x}{\text{Ti}}_{2\ensuremath{-}x}){\text{O}}_{7\ensuremath{-}x/2}$, in which additional ${\text{Dy}}^{3+}$ replace ${\text{Ti}}^{4+}$ in the pyrochlore ${\text{Dy}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$. Heat capacity measurements indicate that these materials lose the spin ice zero point entropy for $x\ensuremath{\ge}0.3$, sharply contrasting with results on the analogous Ho materials. A finite ac susceptibility is observed as $T\ensuremath{\rightarrow}0$ in both the Ho and Dy materials with $x=0.67$, which suggests that spin fluctuations persist down to $T\ensuremath{\sim}0$. 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.