Competition of magnetic and quadrupolar order parameters in HoB4
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- Okuyama Daisuke
- Department of Physics, Graduate School of Science, Tohoku University
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- Matsumura Takeshi
- Department of Physics, Graduate School of Science, Tohoku University Department of Quantum Matter, ADSM, Hiroshima University
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- Mouri Takuya
- Department of Physics, Graduate School of Science, Tohoku University
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- Ishikawa Naoko
- Department of Physics, Graduate School of Science, Tohoku University
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- Ohoyama Kenji
- Institute for Materials Research, Tohoku University
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- Hiraka Haruhiro
- Institute for Materials Research, Tohoku University
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- Nakao Hironori
- Department of Physics, Graduate School of Science, Tohoku University
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- Iwasa Kazuaki
- Department of Physics, Graduate School of Science, Tohoku University
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- Murakami Youichi
- Department of Physics, Graduate School of Science, Tohoku University
書誌事項
- タイトル別名
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- Competition of Magnetic and Quadrupolar Order Parameters in HoB<SUB>4</SUB>
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抄録
The successive magnetic phase transitions of HoB4 with TN1=7.1 K and TN2=5.7 K have been investigated in detail by neutron and X-ray diffraction. Since Ho ions in the c-plane form a Shastry–Sutherland lattice, geometrical frustration has been expected in this compound. Below TN1, HoB4 exhibits an incommensurate antiferromagnetic order with q=(δ,δ,δ′) (δ=0.022, δ′=0.43), followed by a first-order transition at TN2 into a commensurate order with q=(0,0,0), where four magnetic moments are antiferromagnetically coupled in a unit cell. After determining the magnetic structures of the two phases by neutron powder diffraction, we pay particular attention to diffuse scatterings responsible for the critical behavior. Very broad diffuse scatterings, extending almost to the zone boundary, are observed already in the paramagnetic phase at around q=(0,0,0) and (0,0,1⁄2) with magnetic correlation lengths of ξ<10 Å. Below TN1, a strong diffuse scattering develops in a more concentrated region at around q=(0,0,δ′) with ξ∼30 Å, followed by the appearance of a Bragg peak at (δ,δ,δ′). Simultaneously, a sharp Bragg peak corresponding to q=(0,0,0) also develops at (1,0,1) upon diffuse scattering. This complex critical behavior is discussed from the viewpoint of competing order parameters of magnetic and quadrupolar origins. The striking resemblance of the critical behavior to that of HoB2C2 with a square lattice of Ho is interpreted as a manifestation of a universality for a three-dimensional system with competing magnetic and quadrupolar order parameters and a long-ranged RKKY interaction. It is considered that the microscopic difference in interionic interaction due to the difference in crystal structure becomes less prominent in the critical behavior as the correlation length becomes much larger than the lattice constant. On the other hand, the strong diffuse scattering in HoB4, which is hardly detected in HoB2C2, might be ascribed to geometrical frustration. The softening of the elastic constant in HoB4 and HoB2C2 is also discussed.
収録刊行物
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- Journal of the Physical Society of Japan
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Journal of the Physical Society of Japan 77 (4), 044709-044709, 2008
一般社団法人 日本物理学会
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詳細情報 詳細情報について
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- CRID
- 1390001204197496320
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- NII論文ID
- 130005436397
- 110006649428
- 210000107204
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- NII書誌ID
- AA00704814
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- ISSN
- 13474073
- 00319015
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- NDL書誌ID
- 9461455
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
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