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.

* 非技术性摘要 * 许多铀化合物都显示出不寻常的磁性，其原因在科学界仍然存在很大争议。该项目试图揭示一些潜在的机制，该研究人员将利用中子衍射和高磁场研究的组合。中子衍射是在微观水平上测试材料的结构和磁性的首选技术，而在高磁场中的研究则测量宏观响应。这个项目的目的是提供重要的洞察磁性和原子结构之间的相关性，在这样的化合物。人们普遍认为铀化合物的凝聚力和磁性都受到铀原子电子与相邻原子电子相互作用的强烈影响。社区已经用词了吗？杂交？为了描述这种相互作用，但它还没有被充分纳入现有的理论。该项目的结果旨在准确地查明这一机制。该项目将有助于发展一个强大的材料科学计划，这是一个快速发展的领域，有许多有益的职业机会。NMSU的该计划预计将提高新墨西哥州南部和德克萨斯州西部主要拉美裔社区的科学能力。毫无疑问，铀5 f态和配体电子态之间的杂化效应对于铀金属间化合物中磁矩和长程磁序的发展起着重要作用。尽管如此，到目前为止，还没有完全令人满意的理论模型的磁性在这些材料。这个单一的调查员提出了一个系统的深入研究的作用，杂化的磁序的演变和各向异性的铀金属间化合物。对具有不同化学计量比的同构铀化合物族进行了积极的研究。这些化合物的性质将通过化学取代和/或修改外部变量（如磁场或外部静水压力）调整到临界值。使用中子衍射和高磁场技术相结合，将确定单个化合物的结构和磁性参数。特别强调的是放在测试磁性和原子间的距离，这被认为是密切相关的不同杂交效应的强度之间的相关性。这项研究将为学生提供实践培训，使他们成为中子散射和高磁场设施的合格用户。