Effects of Y Dilution on the Antiferroquadrupolar Ordering in the Tetragonal Compound DyB_2C_2 : Condensed Matter Electronic Properties, etc.

概要

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Antiferroquadrupolar (AFQ) and magnetic transitions in Dy_<1-x>Y_xB_2C_2 (0 ⪇ x ⪇ 0.6) have been investigated on the single-crystalline samples by magnetization and specific heat measurements. As the Y concentration increases, the magnetic transition temperature decreases from 15.3 K at x = 0 to 4.5 K at x = 0.6. The AFQ transition temperature also decreases from 24.7 K at x = 0 to 7.4 K at x = 0.6, although it becomes unclear for x ⪈ 0.5 in the magnetization. A λ-type peak of specific heat at T_Q becomes broader as x increases, and changess to a small upheaval for x ⪈ 0.5. On the other hand, the field-induced transitions at the boundary between the AFQ and paramagnetic phases are clearly observed in the magnetization processes at 1.5 K x ⪇ 0.6. The behavior of specific heat implies that the AFQ interaction acts strongly in a rather shorter distance than the antiferromagnetic interacting in DyB_2C_2. The Y dilution causes in a wide distribution of the AFQ interaction strength acting on the Dy quadrupoles. Then the AFQ order developes in a wide temperature range, and is almost completed above the magnetic transition temperature.
社団法人日本物理学会の論文
2000-06-15