Hybridization Effects, Bonding Anisotropy and Magnetism in Uranium Intermetallics

铀金属间化合物中的杂化效应、键合各向异性和磁性

• 批准号: 0804032
• 负责人: Heinrich Nakotte
• 金额: --
• 依托单位: New Mexico State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-15 至 2011-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0804032&HistoricalAwards=false
• 关键词: Hybridization; Effects; Bonding; Anisotropy; Magnetism

****NON-TECHNICAL ABSTRACT****Many uranium compounds are known to exhibit unusual magnetic properties, and the reason for that is still heavily disputed within the scientific community. This project attempts to shed some light onto the underlying mechanisms, and this investigator will utilize a combination of neutron-diffraction and high-magnetic-field studies. Neutron diffraction has been the technique of choice when it comes to testing structural and magnetic properties of a material at a microscopic level, and studies in high magnetic fields measure the macroscopic response. This project is intended to provide important insight into the correlations between magnetism and atomic configuration in such compounds. It is widely accepted that both the cohesive and the magnetic properties of uranium compounds are strongly influenced by interactions of electrons belonging to uranium atoms with the electrons of neighboring atoms. The community has phrased the term ?hybridization? in order to describe such interactions, but it has not been adequately included into existing theories. The results of this project are intended to pinpoint exactly that mechanism. This project will contribute to the development of a strong Materials Science program, a fast-growing field with many rewarding career opportunities. The program at NMSU is expected to increase scientific capacity in the predominantly hispanic communities in Southern New Mexico and Western Texas.****TECHNICAL ABSTRACT****There is little doubt that hybridization effects between the uranium 5f states and the electronic states of the ligands play a prominent role for the development of magnetic moments and long-range magnetic order in uranium intermetallics. Even so, to date, there is no fully satisfactory theoretical model of the magnetism in these materials. This single investigator proposes a systematic in-depth study of the role of hybridization for the evolution of magnetic order and its anisotropy in uranium intermetallics. A vigorous study on families of isostructural uranium compounds with different stoichiometries will be performed. The properties of these compounds will be tuned to critical values by chemical substitutions and/or modifying external variables, such as magnetic fields or external hydrostatic pressure. Using a combination of neutron-diffraction and high-magnetic-field techniques, the structural and magnetic parameters of the individual compounds will be determined. Particular emphasis is put onto testing the correlation between magnetism and interatomic distances, which is believed to be intimately related to the strength of different hybridization effects. The research will provide hands-on training for students to become qualified users at neutron-scattering and high-magnetic-field facilities.

****非技术摘要****许多铀化合物都表现出异常的磁性特性，而科学界仍然存在激烈争议的原因。该项目试图对基本机制进行一些启示，该研究者将利用中子 - 划分和高磁场研究的结合。在测试显微镜水平的材料的结构和磁性时，中子衍射一直是首选技术，并且在高磁场中的研究测量了宏观反应。该项目旨在提供有关此类化合物中磁性和原子配置之间相关性的重要见解。人们普遍认为，铀化合物的凝聚力和磁性都受到铀原子与相邻原子电子的电子相互作用的强烈影响。社区是否表达了“杂交”一词吗？为了描述这种互动，但尚未将其足够包含在现有理论中。该项目的结果旨在准确指出该机制。该项目将有助于开发强大的材料科学计划，这是一个快速发展的领域，并拥有许多有意义的职业机会。 NMSU的该计划有望提高新墨西哥州南部和德克萨斯州西部西班牙裔社区的科学能力。配体对于铀间金属中的磁矩和远距离磁顺序的发展起着重要作用。即便如此，迄今为止，这些材料中磁性的理论模型还没有完全令人满意的理论模型。该单一研究者提出了一个系统的深入研究，对杂交对磁序的演变及其各向异性在铀间层中的演变中的作用。将对具有不同化学计量法的同构铀化合物的家族进行有力的研究。这些化合物的特性将通过化学取代和/或修饰外部变量（例如磁场或外部静水压力）调节至临界值。使用中子 - 分流和高磁场技术的组合，将确定单个化合物的结构和磁参数。特别强调磁性和原子间距离之间的相关性，这被认为与不同杂交效应的强度密切相关。这项研究将为学生提供动手培训，使学生成为中子散落和高磁场设施的合格用户。