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Now showing items 1 - 12 of 12

  • Spin-Orbit and Coulomb Effects in Single-Layered Ruthenates

    Zhang, Guoren   Pavarini, Eva  

    Single-layered ruthenates continue to surprise us decades after their discovery. Here we briefly review some recent advances in the understanding of their electronic properties. They have been obtained via the LDA + DMFT method, the state-of-the-art approach for strongly correlated systems. In particular, we discuss the effects of the spin-orbit interaction and its interplay with the crystal field in the presence of electron-electron repulsion. We focus on the Fermi surface of Sr2RuO4 and the metal-insulator transition in Ca2-xSrxRuO4.
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  • Optical conductivity, Fermi surface, and spin-orbit coupling effects in

    Zhang, Guoren   Pavarini, Eva  

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  • Mott transition, spin-orbit effects, and magnetism in

    Zhang, Guoren   Pavarini, Eva  

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  • : Spin-Orbit and Anisotropic Coulomb Interaction Effects

    Zhang, Guoren   Gorelov, Evgeny   Sarvestani, Esmaeel   Pavarini, Eva  

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  • Electronic structure and magnetism of La4Ni3O8 from first principles

    Liu, Ting   Zhang, Guoren   Zhang, Xiaoli   Jia, Ting   Zeng, Zhi   Lin, H. Q.  

    The magnetic and electronic properties of La4Ni3O8 are investigated by performing the full-potential linearized augmented plane wave method. The C-type antiferromagnetic spin ordering is preferred and a molecular correlated insulating state with high-spin Ni ions is found. Our results have proved that this insulating state is caused by a correlation effect and the strong interlayer interaction. Such strong interlayer coupling results from the high-spin occupation of Ni ions.
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  • rare earth) cobaltates

    Zhang, Guoren   Gorelov, Evgeny   Koch, Erik   Pavarini, Eva  

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  • Orbitally driven spin-singlet state in LiVS(2)

    Guo, Ying   Zhang, Guoren   Zhang, Xiaoli   Jia, Ting   Zeng, Zhi  

    Based on first-principles electronic structure calculations with a full-potential linearized augmented plane wave method and the exact diagonalization of a three-site cluster within a degenerate Hubbard model, we study the orbital and spin properties of the transition metal compound LiVS(2) with a two-dimensional triangular lattice. It is found that in a triangle of three V(3+) ions, the orbital ordering with three t(2g) orbitals alternately occupied by two electrons on each V(3+) ion has developed, which corresponds to the valence-bond solid state of trimerization. The spin-singlet state of the trimer originates from such an orbital ordering and the stronger antiferromagnetic exchange interaction J(A), compared with Hund's rule exchange interaction J(H). By conducting comparative studies of LiVO(2), LiVS(2), and LiVSe(2), we find that the significantly large V-V bond length and d-p hybridization negatively impact the formation of orbital ordering. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562452]
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  • Magnetic frustration in alpha-NaMnO(2) and CuMnO(2)

    Jia, Ting   Zhang, Guoren   Zhang, Xiaoli   Guo, Ying   Zeng, Zhi   Lin, H. Q.  

    The magnetic and electronic properties of alpha-NaMnO(2) and delafossite CuMnO(2) are investigated using a full-potential linearized augmented plane wave method. For the monoclinic structure at room temperature, CuMnO(2) behaves like a frustrated spin-lattice. For the triclinic structure at low temperature, the obtained magnetic configurations of the lowest energy for both alpha-NaMnO(2) and CuMnO(2) are consistent with experiments. However, the exchange constants are all positive. This reveals that the magnetic frustration is only partially relieved at low temperature. It is also found that the Mn(3+) ions are in a high-spin state. Taking into account the on-site Coulomb correlations, our results show that alpha-NaMnO(2) and CuMnO(2) are charge-transfer insulators. (C) 2011 American Institute of Physics. [doi:10.1063/1.3536533]
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  • KAgF(3): Quasi-one-dimensional magnetism in three-dimensional magnetic ion sublattice

    Zhang, Xiaoli   Zhang, Guoren   Jia, Ting   Guo, Ying   Zeng, Zhi   Lin, H. Q.  

    The electronic structure and magnetic properties of the Jahn-Teller-distorted perovskite KAgF(3) have been investigated using the full-potential linearized augmented plane-wave method. It is found that KAgF(3) exhibits significant quasi-one-dimensional antiferromagnetism with the ratio of exchange constant vertical bar J perpendicular to vertical bar (perpendicular to the z-axis) and J (along the z-axis) about 0.04, although the sublattice of magnetic ion is three-dimensional. The strong quasi-one-dimensional antiferromagnetism originates from the C-antiferro-distortive orbital ordering of the Ag(2+) 4d(9) ions. The orbital ordered antiferromagnetic insulating state in KAgF(3) is determined by on-site Coulomb repulsion to a large extent. (C) 2011 Elsevier By. All rights reserved.
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  • ELECTRONIC STRUCTURE AND OPTICAL PROPERTIES OF A PHOTOLUMINESCENT TANTALITE: EuKNaTaO(5)

    Zhang, Xiaoli   Zhang, Guoren   Jia, Ting   Guo, Ying   Zeng, Zhi  

    The electronic structure and linear optical properties of luminescent material EuKNaTaO(5) are investigated by employing full-potential linear augmented plane wave method. Our results show highly localized Eu 4f states which pinned in the energy range below the unoccupied Ta 5d states and over the occupied O 2p states. The optical spectra are analyzed and interpreted in terms of the electronic structure. It is found that Eu ions absorb the major parts of the incident energy below 3.3 eV. This is in accordance with the experimental result that EuKNaTaO(5) phosphor is efficient under the excitation of 535 nm (2.3 eV) visible part of the spectrum. The linear optical properties are found to be anisotropic.
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  • The First Discovery of Eosestheria in Eastern Liaoning, China

    WU, Zijie   WANG, Haipeng   GAO, Fuliang   ZHANG, Guoren   WANG, Mincheng  

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  • alpha-K2AgF4:Ferromagnetism induced by the weak superexchange of different e(g) orbitals from the nearest neighbor Ag ions

    Zhang, Xiaoli   Zhang, Guoren   Jia, Ting   Zeng, Zhi   Lin, H. Q.  

    We study the abnormal ferromagnetism in alpha-K2AgF4, which is very similar to high-T-C parent material La2CuO4 in structure. We find out that the electron correlation is very important in determining the insulating property of alpha-K2AgF4. The Ag(II) 4d(9) in the octahedron crystal field has the t(2g)(6)e(g)(3) electron occupation with e(g) x(2)-y(2) orbital fully occupied and 3z(2)-r(2) orbital partially occupied. The two e(g) orbitals are very extended indicating both of them are active in superexchange. Using the Hubbard model combined with Nth-order muffin-tin orbital (NMTO) downfolding technique, it is concluded that the exchange interaction between e(g) 3z(2)-r(2) and x(2)-y(2) from the first nearest neighbor Ag ions leads to the anomalous ferromagnetism in alpha-K2AgF4. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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