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Studium nových silně korelovaných elektronových sloučenin REnTIn3n+2
Bartha, Attila ; Kratochvílová, Marie (advisor) ; Pospíšil, Jiří (referee)
We have studied two different systems; RE2CoIn8 (RE = Pr, Nd, Dy) and CenTIn3n+2 (T = Pd, Pt; n = 2, 3). All compounds were prepared for the first time in the single crystalline form using the self-flux method. X-ray diffraction confirmed the tetragonal Ho2CoGa8 structure type for the RE2CoIn8 compounds and for the new phase Ce2TIn8. The novel phase Ce3PtIn11 adopts the structure of the Ce3PdIn11 compound, which represents a new structure type. Magnetic measurements revealed low anisotropy and the c-axis as the easy axis for all RE2CoIn8 compounds. Pr2CoIn8 is a paramagnet, while Nd2CoIn8 and Dy2CoIn8 order antiferromagnetically. Magnetization and specific heat measurements of Dy2CoIn8 revealed complex magnetic field-temperature phase diagram with various types of magnetic ordering. Specific heat measurements on multiphase Ce-Pd-In system revealed superconducting transition at Tc = 0.69 K arising from Ce2PdIn8 and another magnetic transition from Ce3PdIn11 at ~ 1.7 K. Ce3PdIn11 and Ce3PtIn11 compounds reveal two, probably magnetic transitions at T1 = 1.6 K, T2 = 1.45 K and T1 = 2.1 K and T2 = 2.0 K, respectively. Specific heat data qualifies both materials as heavy fermion compounds with γ = 290 mJ.mol-1 Ce K-2 and γ = 300 mJ.mol-1 Ce K-2 respectively.
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Specific heat of the R2TIn8 compounds
Vlášková, Kristina ; Javorský, Pavel (advisor) ; Svoboda, Pavel (referee)
This thesis deals with magnetic properties of antiferromagnets Nd2TIn8, where T = Rh, Ir and Co. This compounds are members of a group of structurally rela- ted compounds RX3, RTX5 and R2TX8, crystallizing in tetragonal structure, and they reveal interesting magnetic properties, for example there was observed su- perconductivity for Ce-based compounds. In addition there are shown the results of measurement of NdPd5Al2. Specific heat was measured on monocrystals. The order tempratures were determined. The dimensionalities of magnon excitations where estimated using an analysis of low-temperature dependence of specific heat. The magnetic entropies at order temperature were calculated and they were used for determining the ground states of ions Nd3+ and Tm3+ . The treatment of spe- cific heat above the order temperature was used for determining the energy levels of ions in studied compounds. The NdPd5Al2 specific heat was measured at zero and nonzero external fields, this measuring reveals an antiferromagnetic order under the order temperature and the axis of an easy magnetization in direction of c axis. 1
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Studium nových silně korelovaných elektronových sloučenin REnTIn3n+2
Bartha, Attila ; Kratochvílová, Marie (advisor) ; Pospíšil, Jiří (referee)
We have studied two different systems; RE2CoIn8 (RE = Pr, Nd, Dy) and CenTIn3n+2 (T = Pd, Pt; n = 2, 3). All compounds were prepared for the first time in the single crystalline form using the self-flux method. X-ray diffraction confirmed the tetragonal Ho2CoGa8 structure type for the RE2CoIn8 compounds and for the new phase Ce2TIn8. The novel phase Ce3PtIn11 adopts the structure of the Ce3PdIn11 compound, which represents a new structure type. Magnetic measurements revealed low anisotropy and the c-axis as the easy axis for all RE2CoIn8 compounds. Pr2CoIn8 is a paramagnet, while Nd2CoIn8 and Dy2CoIn8 order antiferromagnetically. Magnetization and specific heat measurements of Dy2CoIn8 revealed complex magnetic field-temperature phase diagram with various types of magnetic ordering. Specific heat measurements on multiphase Ce-Pd-In system revealed superconducting transition at Tc = 0.69 K arising from Ce2PdIn8 and another magnetic transition from Ce3PdIn11 at ~ 1.7 K. Ce3PdIn11 and Ce3PtIn11 compounds reveal two, probably magnetic transitions at T1 = 1.6 K, T2 = 1.45 K and T1 = 2.1 K and T2 = 2.0 K, respectively. Specific heat data qualifies both materials as heavy fermion compounds with γ = 290 mJ.mol-1 Ce K-2 and γ = 300 mJ.mol-1 Ce K-2 respectively.
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