  A spin-ice compound dysprosium titanate, Dy2Ti2O7, is studied by specific
heat measurements in magnetic fields applied along the [110] direction of the
cubic unit cell. Above a magnetic field of 0.4 T a relatively sharp peak at T =
1.1 K in the specific heat appears from a broad peak associated with spin-ice
freezing at low fields. This new peak is almost independent of field up to 1.5
T, while another broad, field-dependent peak is detected at higher temperature.
Under magnetic field along [110] Ising spins on the pyrochlore lattice can be
considered to form two orthogonal sets of chains; parallel and perpendicular to
the field direction. It is suggested that these perpendicular chains behave as
unique ferromagnetic Ising spin chains without long-range order.
