Structural Instability and Magnetic Ordering in a Uranium-based Temary Compound

铀基三元化合物的结构不稳定性和磁有序性

• 批准号: 07454084
• 负责人: FUJITA Toshizo
• 金额: $ 5.06万
• 依托单位: HIROSHIMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454084/
• 关键词: uranium-based ternary compound; semiconductor-metal transition; magnetic transition; structural transition; complex transition; low-temperature X-ray diffraction in magnetic field; structural analysis; elastic moduli; 半導体一金属相転移

The uranium-based ternary compound UNiSn undergoes a semiconductor-metal transition and an antiferromagnetic transition simultaneously at 43K.In addition, we have obtained a preliminary cvidence that the complex transition is accompanied by lattice deformation. In the present study, we investigated how these three instabilities affect each other. Our works are summarized as follows.(1) An X-ray diffractometer was modified so that crystal structures are analyzed in magnetic field upto 8 tesla at low temperatures down to 3.5K.(2) We measured specific heat, Mossbauer spectra, magnetic susceptibility, X-ray diffraction and elastic moduli of UNiSn around 43K.(3) We found that applied magnetic field separates structural transition from antiferromagnetic transition.(4) Partial substitution of Th for U separates the system into two phases with different Th concentration. The antiferromagnetic transition temperature decreases in both phases with increasing The concentration.(5) The quadrupole ordering is responsible for the lattice deformation from a high-temperature cubic structure to a low-temperature orthorhombic one. This suggests the nature of the doublet ground state of f electrons in the uranium-based compounds.The experiments were extended to other ternary compounds which contain uranium or cerium.

铀基三元化合物UNiSn在43 K时同时发生了超导-金属转变和反铁磁转变，并初步证实了这种复杂的转变伴随着晶格形变。在本研究中，我们研究了这三种不稳定性如何相互影响。我们的工作总结如下。(1)对X射线衍射仪进行了改进，以便在高达8特斯拉的磁场和低至3.5K的低温下分析晶体结构。(2)测量了43 K附近的比热、穆斯堡尔谱、磁化率、X射线衍射和弹性模量。(3)我们发现外加磁场将结构转变与反铁磁转变分开。(4)Th部分替代U将体系分成具有不同Th浓度的两相。反铁磁转变温度在两个阶段随着浓度的增加而降低。(5)四极有序是导致高温立方结构向低温斜方结构转变的主要原因。这表明了铀基化合物中f电子的二重基态的性质。实验还推广到其它含铀或铈的三元化合物。

项目成果

K. Izawa et al.: "Different Electronic Ground States in the Hexzgonal and Cubic Phases of UAu_2Sn" J. Phys. Soc. Jpn.65 (10). 3260-3265 (1996)

K. Izawa 等人：“UAu_2Sn 六方相和立方相中的不同电子基态”J. Phys。

Y.Maeda, T.Takabatake, Y.Bando, H.Fujii, K.Oda, K.Sugiyama, K.Kido, K.Izawa, T.Suzuki, T.Fujita and Y.Morii: "Double Magnetic Transitions in UPt_2In" Physica. B223 & 224. 228-230 (1996)

Y.Maeda、T.Takabatake、Y.Bando、H.Fujii、K.Oda、K.Sugiyama、K.Kido、K.Izawa、T.Suzuki、T.Fujita 和 Y.Morii：“UPt_2In 中的双磁转变

T.Suzuki et al.: "Huge Lattice Softening in CeRu_2 without Structural Transition" J.Phys.Soc.Jpn.65(9). 2753-2756 (1996)

T.Suzuki 等人：“CeRu_2 中无结构转变的巨大晶格软化”J.Phys.Soc.Jpn.65(9)。

K.Izawa et al.: "Different Electronic Ground States in the Hexagonal and Cubic Phases of UAu_2Sn" J.Phys.Soc.Jpn.65(10). 3260-3265 (1996)

K.Izawa 等人：“UAu_2Sn 六方相和立方相中的不同电子基态”J.Phys.Soc.Jpn.65(10)。

K.Izawa et al.: "The Origin of Magnetic Field Dependence of Specific Heat in Single-Crystalline CeNiSn" J.Phys.Soc.Jpn.65(10). 3119-3122 (1996)

K.Izawa 等人：“单晶 CeNiSn 中比热的磁场依赖性的起源”J.Phys.Soc.Jpn.65(10)。