Electronic Structure and Magnetism

The fundamental magnetic properties of iron, cobalt, and nickel are the center of interest, beginning with historical attempts and Stoner’s theory. Stoner susceptibility is derived in a modern way by Janak finding that only those three carry a magnetic moment in elementary metals. The energy-band structures of all transition elements are connected with their repective phase stability which is obtained by means of density-functional calculations. The band structure of the ferromagnetic metals is obtained and compared with angle-resolved photoemission data. The electronic structure of the antiferromagnetic metals, Cr, Mn, and fcc Fe is clarified. Next, the magnetic moments of transition-metal compounds are classified by means of the Slater–Pauling curve and a large number of compounds are half-metallic supplying spin-polarized transport. Multilayers realize oscillatory exchange and show unusual electronic properties such as giant magnetoresistance which is discussed in detail. Tunnel junctions supply spin valves. Relativistic effects in solids are of importance for magnetocrystalline anisotropy and spectroscopic effects. Kubo theory supplies the basic understanding of the magneto-optical Kerr effect for which a number of examples are given. Noncollinear magnetic order reveals novel interaction mechanisms, such as the Dzyaloshinsky–Moriya interaction. The Berry phase explains the anomalous Hall effect as well as the Nernst effect and leads to the field of topology in the solid state. Weyl fermions are also explored.

Specific features of the electronic structure of CoxTiSe2 according to the resonant photoemission data

The effect of atomic ordering in the Co sublattice on the electronic structure of the CoxTiSe2 compounds has been studied using a complex of spectral techniques – XPS, XAS, and ResPES, along with theoretical calculations of the total and partial DOS.

Statistics of work and orthogonality catastrophe in discrete level systems: an application to fullerene molecules and ultra-cold trapped Fermi gases

The sudden introduction of a local impurity in a Fermi sea leads to an anomalous disturbance of its quantum state that represents a local quench, leaving the system out of equilibrium and giving rise to the Anderson orthogonality catastrophe. The statistics of the work done describe the energy fluctuations produced by the quench, providing an accurate and detailed insight into the fundamental physics of the process. We present here a numerical approach to the non-equilibrium work distribution, supported by applications to phenomena occurring at very diverse energy ranges. One of them is the valence electron shake-up induced by photo-ionization of a core state in a fullerene molecule. The other is the response of an ultra-cold gas of trapped fermions to an embedded two-level atom excited by a fast pulse. Working at low thermal energies, we detect the primary role played by many-particle states of the perturbed system with one or two excited fermions. We validate our approach through the comparison with some photoemission data on fullerene films and previous analytical calculations on harmonically trapped Fermi gases.

Band Structure Calculations for EuCo2X2 (X = Ge, Si) and EuM5 (M = Cu, Ni)

Band structure calculations for EuCo2X2 (X = Si, Ge) and EuM5¬ (M = Ni, Cu) were performed using FP-LAPW and FPLO DFT codes. Correlations were taken into account within Around Mean Field (AMF) and Fully Localized Limit (FLL) approaches. Antiferromagnetic supercell was constructed for EuCo2X2. Several exchange-correlation potentials were used for EuM5. Equilibrium lattice parameters were calculated for EuM5 and used to study the magnetic properties. Calculated europium valence is between 2.3 and 2.5 and slightly higher for EuNi5 and EuCo2Si2 than for EuCu5 and EuCo2Ge2. LSDA+U calculations within the AMF double-counting scheme are in better agreement with photoemission data than calculations using the FLL approach.