  The low temperature magnetic properties of pyrochlore compound Dy2Ti2O7 in
magnetic fields applied along the [111] direction are reported. Below 1 K, a
clear plateau has been observed in the magnetization process in the field range
2~9 kOe, followed by a sharp moment jump at around 10 kOe that corresponds to a
breaking of the spin ice state. We found that the plateau state is disordered
with the residual entropy of nearly half the value of the zero-field state,
whose macroscopic degeneracy comes from a frustration of the spins on the
kagome layers perpendicular to the magnetic field.
