Study of Internal Field in the Magnetic Ordered Static of the rare-earth hexaboride by the Nuclear Magnetic Resonance

稀土六硼化物磁有序静内场的核磁共振研究

• 批准号: 12640352
• 负责人: SERA Masafumi
• 金额: $ 2.3万
• 依托单位: HIROSHIMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640352/
• 关键词: Orbital Order; Magnetic Order; Multipole; felectron; Kondo Effect; Nuclear Magnetic Resonance; Muon Spin Relaxation; Internal field

CeB_6 is a famous compound showing a mysterious Antiferro-Quadrupolar(AFQ) ordering for 20 years. Very recently, the origin of the mysterious nature in the AFQ ordered state was revealed by Sakai et al. who introduced the AF octupolar (AFO) interaction. However, the microscopic mechanism has not yet been clarified. In order to clarify the unusual nature of the multipolar interaction in CeB_6, we have studied the magnetic, transport and thermal properties of Ce_xR_<1-x>B_6(R=Nd, Gd) system.We found that the impurity Kondo effect exists at high temperatures in the electrical resistivity which is quite similar to that in Ce_xLa_<1-x>B_6. We also found that the Kondo effect continues to exist even in the long range AF magnetic ordered sate although the Ce ion contributes to the AF magnetic ordering. The ground state of the Ce ion in a small x region and for x>0.3 is the localized state but the Kondo singlet for 0.1<x<0.3. We expect that the present results promote the study of the Kondo ef … More fect in the long range AF magnetic ordering. The magnetic phase diagram of Ce_xNd_<1-x>B_6 was completed and found that phase II exists down to x=0.5 and disappears foe x<0.4. From these results, the AFQ interaction is suppressed rapidly with decreasing x below x=0.5, being different from the case of Ce_xLa_<1-x>B_6 where phase II continues to exist down to x〜0.3.We studied the Ce_xGd_<1-x>B_6 system and found that the Gd doping suppresses the AFQ interaction but enhances the AFO one.We analyzed the NMR results in phases II and III of CeB_6 and could succeeded to separate the contribution from the AF octupolar and AFQ moments. We also could observe the unusual magnetic field induced AF magnetic component, which we predicted by the mean field calculation for the 4 sublattice model. Through these studies, we could clarify the origin of the unusual properties in phases II and III as the result of the competition between three of the AFQ, AFO and AF exchange interactions.We found that Yb_<1-x>La_xB_6 in a small x region exhibits the ferromagnetic ordering at T〜150K. This work will be the clue to clarify the origin of the ferromagnetic ordering in CaB_6 system. Less

CeB_6是一种著名的化合物，20年来一直呈现出神秘的反铁四极序（AFQ）。最近，Sakai等人引入了AFQ八极相互作用（AFO），揭示了AFQ有序状态中神秘性质的起源。然而，微观机制尚不清楚。为了阐明CeB_6中多极相互作用的不寻常性质，我们研究了Ce_xR_<1-x>B_6（R=Nd, Gd）体系的磁性、输运和热性质。我们发现，在高温下，在电阻率中存在杂质近藤效应，这与Ce_xLa_<1-x>B_6的电阻率非常相似。我们还发现，近藤效应即使在远距离AF磁有序状态下也继续存在，尽管Ce离子有助于AF磁有序。在一个小的x区域，当x >.3时，Ce离子的基态是局域态，而当0.1<x<0.3时，近藤单重态是局域态。我们期望本研究结果能促进近藤效应在远距AF磁有序中的研究。完成了Ce_xNd_<1-x>B_6的磁相图，发现II相在x=0.5以下存在，在x<0.4时消失。与Ce_xLa_<1-x>B_6在x ~ 0.3时相继续存在不同，在x=0.5以下，AFQ相互作用随着x的减小而迅速被抑制。我们研究了Ce_xGd_<1-x>B_6体系，发现Gd掺杂抑制了AFQ相互作用，但增强了AFO相互作用。我们分析了CeB_6的II和III相的核磁共振结果，并成功地分离出AF八极矩和AFQ矩的贡献。我们还可以观察到异常磁场诱导的AF磁分量，这是我们通过4亚晶格模型的平均场计算预测的。通过这些研究，我们可以澄清第II期和第III期不寻常性质的起源，这是AFQ、AFO和AF交换相互作用三者之间竞争的结果。我们发现Yb_<1-x>La_xB_6在T ~ 150K时表现出铁磁有序。这项工作将为阐明CaB_6系铁磁有序的起源提供线索。少

项目成果

M.Sera: "Anomalous Temperature Dependence of the Magnetic Field Induced Antiferro-Magnetic Moment in the Antiferro-Quadrupolar Ordered State of CeB_6"Phys. Rev. Lett.. 86. 1578-1581 (2001)

M.Sera：“CeB_6 反铁四极有序态中磁场感应反铁磁矩的异常温度依赖性”Phys。

T.Nagata: "Antiferromagnetic Ordering in the spin-ladder compound ; Sr_<14-x>Ca_xCu_<24>O_<41>"J. Phys. Soc. Jpn.. 71. 2419-2424 (2001)

T.Nagata：“自旋梯化合物中的反铁磁有序性；Sr_<14-x>Ca_xCu_<24>O_<41>”J。

S.Kobayashi: "Anisotropic Magnetic Phase Diagram of PrB_6 dominated by the O_<xy> Antiferro-quadrupolar Interaction"J. Phys. Soc. Jpn.. 70. 1721-1730 (2001)

S.Kobayashi：“O_<xy>反铁四极相互作用主导的PrB_6各向异性磁相图”J。

H. Takagiwa: "Magnetic Properties in Phase IV of Ce_<0.7>La_<0.3>B_6 Studied by Muon Spin Relaxation"J. Phys. Sac. Jpn.. 71. 31-34 (2002)

H. Takagiwa：“通过μ子自旋弛豫研究Ce_<0.7>La_<0.3>B_6 IV相的磁性”J。

Y.Uwatoko: "Effect of Pressure on the antiferro-quadrupolar transition in CeB_6"Physica B. 281-282. 555-556 (2000)

Y.Uwatoko：“压力对 CeB_6 中反铁四极转变的影响”Physica B. 281-282。