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Electronic properties and structure of selected rare earth and uranium compounds: influence of impurities
Pospíšil, Jiří ; Sechovský, Vladimír (advisor) ; Schneeweiss, Oldřich (referee) ; Sedmidubský, David (referee)
Title: Electronic properties and structure of selected rare earth and uranium compounds; influence of impurities Author: Jiří Pospíšil Abstract: This thesis is devoted to studies of influence of impurities and/or chemical varieties on magnetic and superconducting properties of selected metallic materials containing rare earth and uranium. The research generally consisted of the defined preparation of studied materials, detailed composition and structure characterisation, experiments focussed on determination of mutually related magnetic, transport and thermal properties followed by data analysis of relations between material composition/quality and material properties. The technology phase was carried out in two ways - 1) preparation of the best pure materials as possible and 2) controlled doping of pure materials. Three main study cases have been chosen: SmPd2Al3 - the representative of the complex magnetism of the Sm3+ ion, the so far unexplored superconductor YPd2Al3 were selected as the RE materials candidates and the controversial ferromagnetic superconductor UCoGe. The key ingredient of the initial technology phase was the refining the commercially available best element metals to the laboratory best achievable purity grade by the unique Solid State Electrotransport (SSE) method. SSE has been also...
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Thermodynamic and transport properties materiáls based on Bi2Se3
Janíček, Petr ; Sechovský, Vladimír (advisor) ; Diviš, Martin (referee)
Single crystals of Bi2Se3 doped with Mn (cMn=0 - 3,0.1019 atoms/cm3) atoms were grown using a modified Bridgman method. Prepared samples were characterized by X-ray diffraction analysis, reflectivity measurement in the plasma resonance frequency region, temperature and magnetic field dependences of the transport coefficients (electrical conductivity, Hall constant), by magnetization measurements (measurement of magnetization curves and temperature dependence of molar magnetic susceptibility) and by measurements of specific heat. The measuremens of above mentioned quantities revealed that the incorporation of Mn atoms to crystal structure leads to increase the free electrons concentration as well as mobility of free electrons. Valence of manganese atoms is according to the magnetic measurements Mn2+. These effects are explained on the point defect model, which is based on idea that the Mn impurity creates substitutional defects Mn'Bi and decreases concentration of antistructure defects Bi 'Se at the same time.
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