Hybridization Effects, Bonding Anisotropy and Magnetism in Uranium Intermetallics

*非技术摘要*许多铀化合物都具有不同寻常的磁性，其原因在科学界仍存在严重争议。这个项目试图阐明一些潜在的机制，这位研究员将利用中子衍射和强磁场研究的组合。在微观水平上测试材料的结构和磁性时，中子衍射一直是首选的技术，而在强磁场中的研究则测量宏观响应。该项目旨在为这类化合物中磁性和原子构型之间的相关性提供重要的见解。人们普遍认为，铀化合物的内聚性和磁性都受到属于铀原子的电子与邻近原子的电子相互作用的强烈影响。社区已经将术语表述为？杂交？为了描述这种相互作用，但它还没有被充分地纳入现有的理论中。这个项目的结果意在准确地指出这一机制。这个项目将有助于一个强大的材料科学项目的发展，这是一个快速增长的领域，拥有许多有益的职业机会。NMSU的这项计划预计将增加新墨西哥州南部和得克萨斯州西部以西班牙裔为主的社区的科学能力。技术摘要毫无疑问，铀5f态和配体电子态之间的杂化效应对铀金属间化合物中磁矩和长程磁序的发展起着突出的作用。尽管如此，到目前为止，还没有完全令人满意的理论模型来描述这些材料中的磁性。这位研究人员对杂化对铀金属间化合物磁序及其各向异性演化的作用进行了系统深入的研究。将对具有不同化学计量比的等结构铀化合物家族进行积极的研究。这些化合物的性质将通过化学取代和/或改变外部变量，如磁场或外部静水压力来调节到临界值。结合使用中子衍射和强磁场技术，将确定单个化合物的结构和磁性参数。特别强调测试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实践培训，使他们成为中子散射和强磁场设施的合格用户。

****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.