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Magnetic and transport properties of f-electron compounds under extreme conditions
Míšek, Martin ; Javorský, Pavel (advisor) ; Griveau, Jean-Christophe (referee) ; Reiffers, Marián (referee)
7 Title: Magnetic and transport properties of f-electron compounds under extreme conditions Author: Martin Míšek Department/Institute: Department of Condensed Matter Physics Supervisor of the doctoral thesis: Doc. Mgr. Pavel Javorský, Dr., Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University in Prague, Prague, Czech Republic Abstract: This thesis deals with the effect of hydrostatic and uniaxial pressures on the magnetic properties of selected compounds. Main emphasis was given to the ErCo2 compound, its analogs with dysprosium and holmium at the rare-earth site and the influence of Si substitutions for the Co. In the case of pure ErCo2, we observed for the first time the pressure induced change of the type of the magnetic phase transition from the first to second order-type and the decoupling of the ordering of Er and Co magnetic sublattices. These effects were only theoretically predicted in the previously published works. Tiny anomalies in the bulk properties related to the existence and short-range ordering of Co magnetic moments in the paramagnetic phase (T > TC), recently deduced from the XMCD experiments at ambient pressure, were successfully observed in this high pressure study as well. Series of high pressure experiments on the UNiGa single crystal,...
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Structure and magnetic properties of f-electron compounds and their hydrides
Mašková, Silvie ; Havela, Ladislav (advisor) ; Kamarád, Jiří (referee) ; Reiffers, Marián (referee)
Title: Structure and magnetic properties of f-electron compounds and their hydrides Author: Silvie Mašková Department: Deparment of Condensed Matter Physics Supervisor: Doc. RNDr. Ladislav Havela, CSc., Deparment of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague, The Czech Republic Abstract: Magnetic properties were studied in several types of actinide- and lanthanide-based ternary compounds. We have shown indirect that anisotropy of compressibility and thermal expansion can be related to the direction of magnetic moments at U-compounds with "soft" directions (where the closest U-U links are) perpendicular to the moments direction. Comparison of U and RE compounds of the 2-2-1 type indicates that contrary to U compounds, RE compounds can absorb much more hydrogen. The involvement of the f-states in metallic bond, which takes place at actinides and not in lanthanides, makes the U-based compounds apparently more stable against hydrogenation. Basic electronic properties were established for ζ -Pu19Os, which is a close analogy to β-Pu, and for its low-temperature variety η -Pu19Os. The results confirm that the volume is not the main parameter driving Pu properties, as β-Pu with intermediate volume is the most strongly correlated Pu phase. Keywords: uranium compounds,...
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