Field Induced Partial Order in the Spin-Ice Dysprosium Titanate

Neutron scattering has been used to investigate the magnetic correlations in the the spin ice material dysprosium titanate, Dy2Ti2O7. An isotopically enriched sample was used to minimise neutron absorption. In zero field no magnetic order was observed down to 50 mK but the magnetic diffuse scattering was in qualitative agreement with that expected for the disordered low temperature state of dipolar spin ice. Application of a field of ~ 0.8 T in the [100] direction led to long range order. With the field applied in the [1-10] direction a coexistence of long range ferromagnetic and short range antiferromagnetic order was observed. This is attributed to the pinning of only half the spins by the field. The hysteresis loops in both field orientations displayed unusual steps and plateaus.