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Strong 5f Ferromagnetism in UH3-Based Materials Ladislav Havela, Mykhaylo Paukov, Ilya Tkach, Volodymyr Buturlim, Zdenek Matej, Silvie Maskova, Ilja Turek, Martin Divis, Daria Drozdenko, Miroslav Cieslar, Milan Dopita, Zuzana Molcanova and Marian Mihalik MRS Advances / FirstView Article / June 2016, pp 1 - 6 DOI: 10.1557/adv.2016.287, Published online: 27 April 2016

Link to this article: http://journals.cambridge.org/abstract_S2059852116002875 How to cite this article: Ladislav Havela, Mykhaylo Paukov, Ilya Tkach, Volodymyr Buturlim, Zdenek Matej, Silvie Maskova, Ilja Turek, Martin Divis, Daria Drozdenko, Miroslav Cieslar, Milan Dopita, Zuzana Molcanova and Marian Mihalik Strong 5f Ferromagnetism in UH3-Based Materials. MRS Advances, Available on CJO 2016 doi:10.1557/adv.2016.287 Request Permissions : Click here

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MRS Advances © 2016 Materials Research Society DOI: 10.1557/adv.2016.287

Strong 5f Ferromagnetism in UH3-Based Materials Ladislav Havela1, Mykhaylo Paukov1, Ilya Tkach1, Volodymyr Buturlim1, Zdenek Matej1,2, Silvie Maskova1, Ilja Turek1, Martin Divis1, Daria Drozdenko1, Miroslav Cieslar1, Milan Dopita1, Zuzana Molcanova3, and Marian Mihalik3 1 Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague 2, Czech Republic 2 MAX IV Laboratory, Lund University, Fotongatan 2, 225 94 Lund, Sweden 3 Institute of Experimental Physics, Slovak Academy of Sciences, Kosice, Slovakia

ABSTRACT Several diverse types of UH3-based hydrides can be prepared by hydrogenation of bcc Ubased alloys. Pair Distribution Function (PDF) analysis using high-energy X-rays identified that the (UH3)1-xMox hydrides are nanocrystalline, with the structure motif based mainly on the UH3 structure. -UH3 represents a minority component. On the other hand, PDF of the (UH3)1-xZrx hydrides corresponds well to the -UH3 crystal structure. All the hydrides are ferromagnetic, with the Curie temperature TC reaching up to 203 K.

INTRODUCTION Uranium metal interacts with hydrogen gas readily at low (several mbar) pressure, producing ferromagnetic -UH3 with the Curie temperature TC ≈ 170 K. The ferromagnetism is certainly related to the volume expansion (U metal is a weak paramagnet), but such high TCvalue for relatively small shortest U-U spacing, dU-U = 330 pm, remains quite surprizing in the context of the Hill limit rule [1], which suggests that magnetic ordering based on U magnetic moments can be formed for the U-U spacing exceeding the limit ≈ 340 pm. -UH3 has a complicated crystal structure, with large cubic unit cell (a = 664 pm) and two different U positions. Besides that, a transient phase with -UH3 structure was observed, but could be never studied as single phase material. Its simpler structure (a = 416 pm) is characterized by a bcc arrangement of U atoms (i.e. one position only) filled by hydrogen atoms