Ferromagnetic ordering on the triangular lattice in the pyrochlore spin-ice compound Dy₂Ti₂O₇

Ice-rule breaking spin-flip in a pyrochlore spin ice compound Dy ₂Ti₂O₇ has been studied in a field applied near the [112] direction, by means of angle-resolved magnetization measurements. We obtained strong evidence that the magnetization component perpendicular to the kagomé plane undergoes a first-order transition below ∼0.26 K. This transition is driven by a ferromagnetic ordering in the field-decoupled spins on the triangular lattice in Dy₂Ti₂O₇, as predicted theoretically.