Abstract
Actinide materials have various applications that range from nuclear energy to quantum computing. Most current efforts have focused on bulk actinide materials. Tuning functional properties by using strain engineering in epitaxial thin films is largely lacking. Using uranium dioxide (UO2) as a model system, in this work, the authors explore strain engineering in actinide epitaxial thin films and investigate the origin of induced ferromagnetism in an antiferromagnet UO2. It is found that UO2+x thin films are hypostoichiometric (x<0) with in-plane tensile strain, while they are hyperstoichiometric (x>0) with in-plane compressive strain. Different from strain engineering in non-actinide oxide thin films, the epitaxial strain in UO2 is accommodated by point defects such as vacancies and interstitials due to the low formation energy. Both epitaxial strain and strain relaxation induced point defects such as oxygen/uranium vacancies and oxygen/uranium interstitials can distort magnetic structure and result in magnetic moments. This work reveals the correlation among strain, point defects and ferromagnetism in strain engineered UO2+x thin films and the results offer new opportunities to understand the influence of coupled order parameters on the emergent properties of many other actinide thin films.
| Original language | English |
|---|---|
| Article number | 2203473 |
| Journal | Advanced Science |
| Volume | 9 |
| Issue number | 33 |
| DOIs | |
| State | Published - Nov 24 2022 |
Funding
The work at Los Alamos National Laboratory was supported by the NNSA's Laboratory Directed Research and Development (LDRD) Program and was performed, in part, at the Center for Integrated Nanotechnologies (CINT), an Office of Science User Facility operated for the U.S. Department of Energy Office of Science. Los Alamos National Laboratory, an affirmative action equal opportunity employer, was managed by Triad National Security, LLC for the U.S. Department of Energy's NNSA, under contract 89233218CNA000001. M.T.P. acknowledges support from 20220485MFR and 20210640ECR. Y.S. acknowledges support from the G. T. Seaborg Institute under project number 20210527CR. P.R., Z.C, and Q.X.J. acknowledge the CINT User Program. The work at the National High Magnetic Field Laboratory was supported by the U.S. Department of Energy, the State of Florida, and the National Science Foundation through cooperative grant agreements DMR 1157490 and DMR 1644779. M.J. acknowledges the support by the US Department of Energy BES “Science at 100 T” grant, Division of Materials Science and Engineering. P.Y. acknowledges the support from the US Department of Energy, Chemical Sciences, Geosciences, and Biosciences Division, Heavy Element Chemistry program, under contract DE‐AC52‐06NA25396.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | 89233218CNA000001 |
| Office of Science | |
| Laboratory Directed Research and Development | |
| Los Alamos National Laboratory |
Keywords
- actinide materials
- epitaxy
- lattice-strain
- magnetism
- thin films
- uranium dioxide