Magnetocaloric Effect Study on the Pyrochlore Spin Ice Compound Dy_2Ti_2O_7 in a [111] Magnetic Field(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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Field variation of the entropy S(H) of the spin ice compound Dy_2Ti_2O_7 has been examined by means of magnetocaloric effect measurements in a magnetic field H ‖ [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 〜0.8T, 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_<rc> ≃ 0.36 K), S(H) at 0.4 K and 0.5 K exhibits a pronounced peak at the spin flip field of 〜0.9 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.
社団法人日本物理学会の論文
2004-10-15