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Title: Volodymyr Buturlim: U-based hydrides and their magnetism
Number: 200/17
Status: Closing date exceeded
Begin: Středa, Listopad 29, 2017 at 02:30
Tutor: Vladimír Sechovský
Location: lecture room F2, first floor Ke Karlovu 5


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We have a pleasure to invite you to attend the joint seminar
of the Department of Condensed Matter Physics (DCMP)
and the Materials Growth and Measurement Laboratory (MGML) http://mgml.eu.

 

Program

 

U-based hydrides and their magnetism

 

lecture given by:

Volodymyr Buturlim

Charles University, Faculty of Mathematics and Physics, DCMP, Ke Karlovu 5, 12116 Prague, Czech Republic

The seminar takes place in the lecture room F2 
of the Faculty of Mathematics and Physics, Ke Karlovu 5, Praha 2
on Wednesday, 29. 11. 2017 from 14:30 

Vladimír Sechovský
On behalf of the DCMP and MGML


Abstract 

U exhibits three allotropic modifications: orthorhombic a-U (space group Cmcm), tetragonal β-U phase (sp. gr. P42/mmm), and γ-U phase with a body-centered-cubic A2-type structure (space group Im-3m; stable between 1049 K and 1408 K). α-U phase can lead to the formation of two types of hydride either metastable α-UH3 or stable β-UH3. The crystal structure of the metastable α-UH3 is formed by the bcc lattice of U atoms, with the volume expanded by 60% with respect to γ-U phase, β-UH3 is also cubic with bigger unit cell and two additional U sites. Hydrogenation of the bcc U alloys can lead to the formation of nano-crystalline modifications of the mentioned hydride allotropes [1]. Both hydride types are ferromagnets with comparable high Tc (around 170 K). The reason of the ordering at such high Curie temperatures can be tested by tuning the H amount or by alloying with different elements. We found that absorbed hydrogen amount does not change even at 120 Bar hydrogen pressure, while alloyed γ-U does not decompose after hydrogenation. Therefore there is a chance to see how the magnetic properties can be changed due to the presence of different 3d elements. The (UH3)0.87Mo0.13 with nano-crystalline β-UH3 type of structure, for instance, undergoes phase transition around 203K [2]. We have also investigated (UH3)1-xTx  hydrides where T= Ti, Nb, Ru. All of them exhibit an increase of the critical temperature unless certain concentration of the transition element was achieved. Magnetic properties and the possible reasons for the change will be discussed in more details.

In collaboration with: Ladislav Havela1, Sylwia Sowa1,2, Hoa Kim Ngan Nhu-Tarnawska2, Mykhaylo Paukov1, Daria Drozdenko1, Milan Dopita1, Peter Minarik1, Silvie Mašková1, Michal Falkowski1

1Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 12116 Prague, Czech Republic

2Institute of Physics, Pedagogical University, Podchorazych 2, 30 084 Kraków, Poland

 

[1]      L. Havela, M. Paukov, I. Tkach, V. Buturlim, Z. Matej, S. Maskova, I. Turek, M. Divis, D. Drozdenko, M. Cieslar, M. Dopita, Z. Molcanova, M. Mihalik, Strong 5f Ferromagnetism in UH3-Based Materials, MRS Adv. 1 (2016) 2987–2992. doi:10.1557/adv.2016.287.

[2]      M. Paukov, L. Havela, N.-T.H. Kim-Ngan, V. Buturlim, I. Tkach, D. Drozdenko, S. Mašková, S. Sowa, Z. Molcanova, M. Mihalik, M. Krupska, Variations of magnetic properties of UH3 with modified structure and composition, J. Sci. Adv. Mater. Devices. 1 (2016) 185–192. doi:10.1016/j.jsamd.2016.06.005.


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