Realistic Modeling of Complex Oxide Materials

Since electronic and magnetic properties of many transition-metal oxides can be efficiently controlled by external factors such as the temperature, pressure, electric or magnetic field, they are regarded as promising materials for various applications. From the viewpoint of electronic structure, these phenomena are frequently related to the behavior of a small group of states close to the Fermi level. The basic idea of this project is to construct a low-energy model for the states near the Fermi level on the basis of first-principles density functional theory, and to study this model by modern many-body techniques. After a brief review of the method, the abilities of this approach will be illustrated on a number of examples, including multiferroic manganites and spin-orbital-lattice coupled phenomena in RVO3 (R being the three-valent element).Comment: 3 pages, 6 figures, Conference on Computational Physics 200

Magnetic structure of noncentrosymmetric perovskites PbVO3 and BiCoO3

It is well known that if a crystal structure has no inversion symmetry, it may allow for Dzyaloshinskii-Moriya magnetic interactions, operating between different crystallographic unit cells, which in turn should lead to the formation of long-periodic spin-spiral structures. Such a behavior is anticipated for two simple perovskites PbVO3 and BiCoO3, crystallizing in the noncentrosymmetric tetragonal P4mm structure. Nevertheless, we argue that in reality PbVO3 and BiCoO3 should behave very differently. Due to the fundamental Kramers degeneracy for the odd-electron systems, PbVO3 has no single-ion anisotropy. Therefore, the ground state of PbVO3 will be indeed the spin spiral with the period of about one hundred unit cells. However, the even-electron BiCoO3 has a large single-ion anisotropy, which locks this system in the collinear easy-axis C-type antiferromagnetic ground state. Our theoretical analysis is based on the low-energy model, derived from the first-principles electronic structure calculations.Comment: 16 pages, 7 figures, 3 table