| AVS 65th International Symposium & Exhibition | |
| Actinides and Rare Earths Focus Topic | Wednesday Sessions |
| Session AC+MI+SA-WeM |
| Session: | Magnetism, Complexity, and Superconductivity in the Actinides and Rare Earths |
| Presenter: | Evgeniya Tereshina-Chitrova, Institute of Physics, Academy of Sciences of the Czech Republic |
| Authors: | E.A. Tereshina-Chitrova, Institute of Physics, Academy of Sciences of the Czech Republic L. Havela, Charles University, Prague, Czech Republic T. Gouder, Institute for Transuranium Elements, Germany Z. Bao, Institute for Transuranium Elements, Germany M. Dopita, Charles University, Prague, Czech Republic R. Caciuffo, Institute for Transuranium Elements, Germany |
| Correspondent: | Click to Email |
Uranium is the basic component of most nuclear fuels. The production of uranium-based films has advantage over bulk materials studies as it allows performing advanced physics and chemistry experiments on small amounts of radioactive material and on its clean and smooth surfaces. Other interesting field is uranium magnetism. Although uranium itself is non-magnetic, uranium compounds display a rich variety of magnetic phenomena intimately related to the variable character of the 5f electron states [1]. Additional degrees of freedom can be used in thin films, in which the reduced dimensionality and structure modifications far exceed the limits imposed by thermodynamics, obeyed in bulk systems. We review the achievements in the field of sputter-deposited films, in which variations of deposition conditions can dramatically suppress crystallinity of the deposited material. The 5f itinerant magnetic systems (as US or UN [2]) react to the low substrate temperatures and high deposition rates by decreasing ordering temperatures and eventually by the loss of U magnetic moments. The strong ferromagnetism of uranium hydride is, on the other hand, almost insensitive, which underlines its local-moment character.
The possibility to combine films of various materials on the nanostructure scale can also give rise to new functionalities. For example, the exchange bias (EB) effect [3], arising as a result of combination of a ferromagnet biased by exchange interaction at the interface to an antiferromagnet, is particularly interesting if uranium magnetics are involved. The new ingredient, strong spin-orbit interaction, can lead to very strong magnetic anisotropy, which represents an essential parameter. We have been systematically studying films of Fe3O4 (ferromagnet) grown using different substrates on the top UO2, playing the role of biasing antiferromagnet [4]. The resulting high bias field (> 0.2 T) and a proximity effect, in which the high Curie temperature of Fe3O4 provides the EB functionality even at temperatures exceeding ordering of UO2, demonstrate the promising aspects of using actinides in this non-traditional way.
The work is supported by the Czech Science Foundation under the project #18-02344S. Part of the work was supported by “Nano-materials Centre for Advanced Applications,” Project No.CZ.02.1.01/0.0/0.0/15_003/0000485, financed by ERDF.
[1] V. Sechovsky, L. Havela, in: Magnetic Materials, K.H.J. Buschow (Ed.), Elsevier, Amsterdam, 1998, Vol. 11, p. 1.
[2] L. Havela et al., JALCOM 408-412, p. 1320 (2006).
[3] W. H. Meiklejohn and C. P. Bean, Phys. Rev. B 102, 1413 (1956).
[4] E.A. Tereshina et al., Appl. Phys. Lett. 105(12),122405 (2014).