| Project/Area Number |
16204021
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | Tohoku University |
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Principal Investigator |
ONODERA Hideya Tohoku University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (50005972)
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| Co-Investigator(Kenkyū-buntansha) |
KURAMOTO Yoshio Tohoku University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (70111250)
TAKAGI Shigeru Tohoku University, Graduate School of Science, Associate Professor, 大学院理学研究科, 助教授 (20154750)
MATSUOKA Eiichi Tohoku University, Graduate School of Science, Research Associate, 大学院理学研究科, 助手 (20400228)
KIMURA Noriaki Tohoku University, Graduate School of Science, Research Associate, 大学院理学研究科, 助手 (30292311)
東方 綾 東北大学, 大学院・理学研究科, 助手 (40300884)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥46,410,000 (Direct Cost: ¥35,700,000、Indirect Cost: ¥10,710,000)
Fiscal Year 2006: ¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000)
Fiscal Year 2005: ¥10,660,000 (Direct Cost: ¥8,200,000、Indirect Cost: ¥2,460,000)
Fiscal Year 2004: ¥30,680,000 (Direct Cost: ¥23,600,000、Indirect Cost: ¥7,080,000)
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| Keywords | Orbital Order / Antiferromagnetic Order / Antiferroquadrupolar Order / Antiferro-octupolar Order / Magnetic Structure / Magnetic Phase Transition / Magnetic Phase Diagram / Van Vleck Magnetic Transition / 反強四極子相互作用 / 反強磁性相互作用 / 八極子相互作用 / DyB_2C_2 / TbB_2C_2 |
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| Research Abstract |
The present works have been performed with the aim of clarifying the roles of multipolar interactions in the magnetism of rare earth compounds. The results are summarized as follows.
1.We found out a new phase transition and completed the complicated phase diagrams of DyB_2C_2 that had been found by us to show the successive antiferroquadrupolar (AFQ) and antiferromagnetic (AFM) transitions.
2.Neutron diffraction experiments on the Y-diluted DyB_2C_2 single-crystals have revealed that the quadrupolar ordering in DyB_2C_2 is driven by quasi-one-dimensional quadrupolar interactions which consist of extremely strong AFQ interactions along the tetragonal c-axis and weak ferroquadrupolar (FQ) interactions in the basal c-plane. Moreover, the ^<161>Dy Mossbauer experiments, the neighboring Y ion decreases or increases the ^<161>Dy magnetic hyperfine fields depending on the substituted site because of the change of frustration between the AFQ and AFM interactions.
3.The substitution of 20%Dy by Gd brought forth a new transition sequence in which the AFQ transition occurs below the AFM transition temperature.
4.By the Y-dilution of TbB_2C_2, it has been clarified that both the 4f ground state and the first excited state at 40 K are singlets and that the AFM transition and the field-induced AFQ transition concern with the 4f levels including the higher excited states around 150 K, that is, the phase transition is a exchange-induced Van Vleck magnetic transition.
5.The precise examination on the Gd-diluted TbB_2C_2 has revealed that the ground state of TbB_2C_2 is a coexistent phase of AFM order and antiferro-octupolar (AFO) order. The anomalous magnetic behaviors of TbB_2C_2, and the diluted system have been understood satisfactorily based on the (AFQ+AFO) ground state of TbB_2C_2
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