I. Solovyev

Using the rotationally invariant LDA+U approach we investigate the effect of the rhombohedral distortion on the orbital magnetism of FeO. The latter plays a very important role both for stretching and compressive deformations. In the first case, a large orbital magnetic moment is stabilized along the [111] direction of the cube and causes similar reorientation for the spin counterpart. Opposite distortion (compression) turns the magnetic moments to the plane (111) where the orbital component is least quenched.

We argue that the charge ordering observed in 50% doped manganites is a manifestation of the peculiar antiferromagnetic spin ordering. The latter, combined with the large Hund's rule physics in manganites, divides the whole system into the quasi-one-dimensional zigzag objects, which exhibit a very unique electronic structure and behave as band insulators. This results in a strong anisotropy of short-range

The effects of orbital degrees of freedom on the exchange interactions in a quasi-one-dimensional spin-1 antiferromagnet CaV2O4 are systematically studied. For this purpose a realistic low-energy electron model with the parameters derived from the first-principles calculations is constructed in the Wannier basis for the t2g bands. The exchange interactions are calculated using both the theory of infinitesimal spin rotations near the mean-field ground state and the superexchange model, which provide a consistent description. The obtained behaviour of exchange interactions differs substantially from the previously proposed phenomenological picture based on magnetic measurements and structural considerations, namely: (i) despite the quasi-one-dimensional character of the crystal structure, consisting of the zigzag chains of the edge-sharing VO6 octahedra, the electronic structure is essentially three-dimensional, that leads to finite interactions between the chains; (ii) the exchange i...

... TM Rice AT&T Bell Laboratories, Murray Hill, New Jersey 07974 and Theoretische Physik, Eidgenössische Technische Hochschule-Hönggerberg, 8093 Zürich, Switzerland ... led to propose that the crossover observed in zero field arises through proximity to this criti-cal point and ...

We argue that the key parameter responsible for the exchange-correlation enhancement of the orbital magnetic moments in solids is “Hubbard U” rather than the intra-atomic Hund's second rule coupling, being consistent with a more general concept of the orbital ...

ABSTRACT The double ionization energy (DIE) spectra are calculated for the spin-polarized aluminum and sodium clusters by means of the all-electron spin-polarized GW+T-matrix method based on the many-body perturbation theory. Our method using the one- and two-particle Green’s functions enables us to determine the whole spectra at once in a single calculation. The smaller is the size of the cluster, the larger the difference between the minimal double ionization energy and the twice of the ionization potential. This is because the strong Coulomb repulsion between two holes becomes dominant in small confined geometry. Due to Pauli’s exclusion principle, the parallel spin DIE is close to or smaller than the antiparallel spin DIE except for Na4 that has well-separated highest and second highest occupied molecular-orbital levels calculated by the spin-dependent GW calculation. In this paper, we compare the results calculated for aluminum and sodium clusters and discuss the spin-polarized effect and the cluster size dependence of the resulting spectra in detail.