Magnetocaloric effect study on the pyrochlore spin ice compound Dy2Ti2O7 in a [111] magnetic field

Field variation of the entropy S(H) of the spin ice compound Dy2Ti2O7 has been examined by means of magnetocaloric effect measurements in a magnetic field H parallel to [111], with attention focused on the ice-rule breaking spin-flip transition. At T = 0.35 K, S(H) exhibits a plateau in the kagome ice state up to similar to0.8 T, followed by a sharp decrease at 0.9 T where a first-order transition to the saturated state occurs. Slightly above the critical point of the transition (T-cr similar or equal to 0.36 K), S(H) at 0.4 K and 0.5 K exhibits a pronounced peak at the spin flip field of similar to0.9 T indicating an enhanced degeneracy due to coexistence of "two-in, two-out" and "three-in, one-out" states at the field. The peak height of S(H) is, however, strongly temperature dependent and substantially smaller than that expected from a nearest-neighbor spin ice model, suggesting the presence of certain magnetic correlation in the system.