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Electronic structure and magnetic properties of materials with strong electron-electron correlations
Tchaplianka, Maxim ; Shick, Alexander (advisor) ; Janiš, Václav (referee) ; Kronik, Leeor (referee)
Title: Electronic structure and magnetic properties of materials with strong electron-electron correlations Author: Maxim Tchaplianka Department: Institute of Physics of the Czech Academy of Sciences Supervisor: Ing. Alexander B. Shick, CSc., DSc., Institute of Physics of the Czech Academy of Sciences Abstract: In this thesis, we present several computational methods of studying magnetic materials, and apply them to several real materials. Density functional theory with exact diagonalization is used to investigate three materials which consist of a cobalt impurity coupled to a metallic substrate. The observables and spectral densities found in each case are presented. Next, FeHfSb and UFe10Si2 are investigated as potentially magnetically hard materials, via the calculation of their magnetocrystalline anisotropy and thermodynamic stability. Keywords: density functional theory, Anderson impurity model, exact diagonal- ization, magnetic anisotropy, Kondo effect
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Electronic structure and magnetic properties of the materials with strong electron-electron correlation
Kozub, Agnieszka Lidia ; Shick, Alexander (advisor) ; Legut, Dominik (referee) ; Minár, Ján (referee)
In this thesis, we summarize the material-specific theories of strongly correlated systems and apply them to selected materials. We describe and apply the corre- lated band theory methods: the local density approximation plus Coulomb U, and the density functional theory plus exact diagonalization of single impurity An- derson model. First, we investigate the systems containing impurity atoms: cobalt impurity located in the bulk copper and samarium, and neodymium adatoms on the surface of graphene. We present the spectral densities and study the magnetism of those compounds. Afterwards, we analyze three Np-based compounds: NpPt2In7, Np2Ni17 and NpBC. For all three compounds we analyze the spin, orbital and to- tal magnetic moments and the total density of states, as well as its projections for selected orbitals and spins. Moreover, for NpPt2In7 and NpBC we perform the to- tal energy analysis between different magnetic moment arrangements on the Np atoms.
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Topological band theory of relativistic spintronics in antiferromagnets
Šmejkal, Libor ; Jungwirth, Tomáš (advisor) ; Kuneš, Jan (referee) ; Shick, Alexander (referee)
Nanoelectronics and spintronics are concerned with writing, transporting, and reading information stored in electronic charge and spin degrees of freedom at the nanoscale. Past few years have shown that two spintronics effects discovered in the 19th century, namely anisotropic magnetoresistance and anomalous Hall effect, can be used also for sensing antiferromagnetism which opened the field of antiferromagnetic spintronics. The more than a century of controversial studies of these effects have shown their relativistic spin-orbit coupling and spin-polarisation symmetry breaking origin. However, a complete understanding of these effects and a fully predictive theory capable of identifying novel suitable antiferromagnetic materials are still lacking. Here, by extending modern symmetry and topology concepts in condensed matter physics, we have further developed the theory of anisotropic magnetoresistance and spontaneous Hall effect. Our approach is based on magnetic symmetry and topology analysis of antiferromagnetic energy bands, Bloch spectral functions, and Berry curvatures calculated from the state-of-the- art first-principle theory. This guided us to the prediction of two novel, previously unanticipated effects: relativistic metal-insulator transition from antiferromagnetic Dirac fermions, and crystal Hall...
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New binary refractory metal-Fe intermetallic compounds for hard magnet applications
Tchaplianka, Maxim ; Shick, Alexander
We investigate theoretically the electronic and magnetic structure of Fe2Hf. The density functional theory is used to calculate the magnetic moments on individual atoms, the total and projected densities of states, and the magnetic anisotropy energy. The Fe2Hf is found to be metallic and ferrimagnetic, with the magnetic moments of Fe and Hf atoms pointing in the opposite directions. The negative magnetic anisotropy, and the “in-plane” preferential direction of the magnetization are found as a result of theoretical calculations. Our study suggests that the chemical control of the magnetic anisotropy has to be investigated in order to evaluate the potential of Fe2Hf for the permanent magnet applications.\n
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Electronic structure and magnetic properties of the materials with strong electron-electron correlation
Kozub, Agnieszka Lidia ; Shick, Alexander (advisor) ; Legut, Dominik (referee) ; Minár, Ján (referee)
In this thesis, we summarize the material-specific theories of strongly correlated systems and apply them to selected materials. We describe and apply the corre- lated band theory methods: the local density approximation plus Coulomb U, and the density functional theory plus exact diagonalization of single impurity An- derson model. First, we investigate the systems containing impurity atoms: cobalt impurity located in the bulk copper and samarium, and neodymium adatoms on the surface of graphene. We present the spectral densities and study the magnetism of those compounds. Afterwards, we analyze three Np-based compounds: NpPt2In7, Np2Ni17 and NpBC. For all three compounds we analyze the spin, orbital and to- tal magnetic moments and the total density of states, as well as its projections for selected orbitals and spins. Moreover, for NpPt2In7 and NpBC we perform the to- tal energy analysis between different magnetic moment arrangements on the Np atoms.
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