Specific heat of Dy2Ti2O7 in magnetic fields:: comparison between single-crystalline and polycrystalline

We report the specific heat of single crystals of the spin ice compound Dy2Ti2O7 under magnetic fields down to 1.8 K. Our polycrystalline results down to 0.4 K are fully consistent with the previous report by Ramirez et at. For the magnetic field along the [100] direction, C-spin/T is interpreted as one Schottky peak characterized by the Zeemann splitting of the Ising levels of all four equivalent spins for each tetrahedron. However, for the magnetic field along the [111] direction, C-spin/T is interpreted as two-component Schottky peak reflecting the fact that there are two kinds of spin components. Along the [110] direction, it is also interpreted as two-component Schottky peak because of experimental misalignment. We found that the features of the polycrystalline data in magnetic fields cannot be reconstructed by simply taking appropriate averages of the present anisotropic single-crystalline data. (C) 2002 Elsevier Science Ltd. All rights reserved.