Magnetic and Electronic Properties of Complex Oxides from First‐Principles

Abstract

The theoretical treatment of complex oxide structures requires a combination of efficient methods to calculate structural, electronic, and magnetic properties, due to special challenges such as strong correlations and disorder. In terms of a multicode approach, this study combines various complementary first‐principles methods based on density functional theory to exploit their specific strengths. Pseudopotential methods, known for giving reliable forces and total energies, are used for structural optimization. The optimized structure serves as input for the Green's function and linear muffin‐tin orbital methods. Those methods are powerful for the calculation of magnetic ground states and spectroscopic properties. Within the multicode approach, disorder is investigated by means of the coherent potential approximation within a Green's function method or by construction of special quasirandom structures in the framework of the pseudopotential methods. Magnetic ground states and phase transitions are studied using an effective Heisenberg model treated in terms of a Monte Carlo method, where the magnetic exchange parameters are calculated from first‐principles. The performance of the multicode approach is demonstrated with different examples, including defect formation, strained films, and surface properties.

Structure and Magnetism of EuS on Bi2Se3(0001)

“…The approach is a self‐consistent relativistic full‐potential Green function method based on the multiple‐scattering theory and provides an adequate description of bulk materials, surface, interfaces, and real‐space clusters. [ 48–50 ] The goal of our simulations is to study 2 DL of EuS on . The structure model, derived by SXRD, serves as input for our calculations, which are carried out within a generalized gradient approximation (GGA) of the DFT.…”

Eigenmodes of a disordered FeCo magnonic crystal at finite temperatures

“…Magnetic moments µ α i and exchange parameters J ij of iron-cobalt alloys at various concentrations were evaluated using a first-principles Green-function method within a generalized gradient approximation of density functional theory [28]. The method is designed for bulk materials, surfaces, interfaces and real space clusters [29][30][31]. The impact of disorder on the electronic structure was taken into account within the electronic CPA [32] implemented within multiple scattering theory [33].…”

Light-driven topological and magnetic phase transitions in thin-layer antiferromagnets

“…where experiments suggest a nearest-neighbor AFM interlayer interaction SJc = −0.055 meV [66]. We obtain the spin Hamiltonian from first-principle calculations, employing a Green's function approach and the magnetic force theorem [67,68]. The calculations were performed using a GGA+U approximation, which describes adequately localized Mn 3d states with U ef f = U − J=5.2 eV [5,36].…”