Anisotropic release of the residual zero-point entropy in the spin ice compound Dy2Ti2O7:: Kagome ice behavior -: art. no. 014415

We report the specific heat and entropy of single crystals of the spin ice compound Dy2Ti2O7 at temperatures down to 0.35 K. We apply magnetic fields along the four characteristic directions [100], [110], [111], and [112]. Because of Ising anisotropy, we observe anisotropic release of the residual zero-point entropy, attributable to the difference in frustration dimensionality. In the high magnetic field along these four directions, the residual entropy is almost fully released and the activation entropy reaches R ln2. However, in the intermediate-field region, the entropy in the fields along the [111] direction is different from those for the other three field directions. For the [111] direction, the frustration structure changes from that of the three-dimensional pyrochlore to that of a two-dimensional Kagome-like lattice with constraint due to the ice rule, leading to different values of the zero-point entropy.