Hybridization Effects, Bonding Anisotropy and Magnetism in Uranium Intermetallics

New Mexico State University, Las Cruces NM

Investigators

Abstract

****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.