Correlation effects in ferromagnetism of transition metals

Oleś, Andrzej M.; Stollhoff, Gernot

doi:10.1103/physrevb.29.314

Cited by 146 publications

(81 citation statements)

References 30 publications

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“…These can be attributed to the overestimated exchange splitting and its incorrect nearly isotropic behavior over the Brillouin zone in the LSDA. As pointed out by Oles and Stollhoff 79 and by Liebsch, 80 the large exchange splitting in the LSDA is due to the neglect of strong correlation effects within the 3d states and anisotropic exchange. Conse- …”

Section: A Single-particle Stoner Excitationsmentioning

confidence: 89%

Wannier-function approach to spin excitations in solids

et al. 2010

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We present a computational scheme to study spin excitations in magnetic materials from first principles. The central quantity is the transverse spin susceptibility, from which the complete excitation spectrum, including single-particle spin-flip Stoner excitations and collective spin-wave modes, can be obtained. The susceptibility is derived from many-body perturbation theory and includes dynamic correlation through a summation over ladder diagrams that describe the coupling of electrons and holes with opposite spins. In contrast to earlier studies, we do not use a model potential with adjustable parameters for the electron-hole interaction but employ the random-phase approximation. To reduce the numerical cost for the calculation of the four-point scattering matrix we perform a projection onto maximally localized Wannier functions, which allows us to truncate the matrix efficiently by exploiting the short spatial range of electronic correlation in the partially filled d or f orbitals. Our implementation is based on the full-potential linearized augmented-plane-wave method. Starting from a ground-state calculation within the local-spin-density approximation ͑LSDA͒, we first analyze the matrix elements of the screened Coulomb potential in the Wannier basis for the 3d transition-metal series. In particular, we discuss the differences between a constrained nonmagnetic and a proper spin-polarized treatment for the ferromagnets Fe, Co, and Ni. The spectrum of single-particle and collective spin excitations in fcc Ni is then studied in detail. The calculated spin-wave dispersion is in good overall agreement with experimental data and contains both an acoustic and an optical branch for intermediate wave vectors along the ͓1 0 0͔ direction. In addition, we find evidence for a similar double-peak structure in the spectral function along the ͓1 1 1͔ direction. To investigate the influence of static correlation we finally consider LSDA+ U as an alternative starting point and show that, together with an improved description of the Fermi surface, it yields a more accurate quantitative value for the spin-wave stiffness constant, which is overestimated in the LSDA.

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Section: A Single-particle Stoner Excitationsmentioning

confidence: 89%

Wannier-function approach to spin excitations in solids

et al. 2010

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“…While the later behavior may be expected and in fact is observed experimentally [13], the magnetization increase at the interface Fe atoms characterized by a lower coordination of Fe atoms is not obvious. We interpret it as a manifestation of electron correlation effects which increase local moments at Fe atoms when the kinetic energy of 3d electrons is decreased by a lower Fe coordination [17]. In agreement with this interpretation, the moment enhancement at the interface becomes even more pronounced in the extreme case of a single iron ML, where Fe atoms have only platinum coordination and their magnetic moments are increased up to the level of saturation m 3.0 µ B , i.e., by 35% over the bulk iron value m Fe 2.2 µ B (the magnetic moments of Pt atoms at the interface are here quite small m Pt 0.3 µ B ).…”

Section: Magnetic Propertiesmentioning

confidence: 94%

Ab initio calculations of magnetic structure and lattice dynamics of Fe/Pt multilayers

2008

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Abstract. The magnetization distribution, its energetic characterization by the interlayer coupling constants and lattice dynamics of (001)-oriented Fe/Pt multilayers are investigated using density functional theory combined with the direct method to determine phonon frequencies. It is found that ferromagnetic order between consecutive Fe layers is favoured, with the enhanced magnetic moments at the interface. The bilinear and biquadratic coupling coefficients between Fe layers are shown to saturate fast with increasing thickness of nonmagnetic Pt layers which separate them. The phonon calculations demonstrate a rather strong dependence of partial iron phonon densities of states on the actual position of Fe monolayer in the multilayer structure.

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“…[31] and in addition we use a semiempirical formula C 4B for Racah parameters. With this Ansatz one finds J d = 3B + C ≈ 7B for a pure t 2g system [32]. The J d,µν elements concerning e g orbitals are finite and fixed again using the entries from Table I in Ref.…”

Section: The Hamiltonian Parametersmentioning

confidence: 99%

Multibandd−pmodel and self-doping in the electronic structure ofBa2IrO4

Rościszewski

Oleś

2016

Phys. Rev. B

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We introduce and investigate the multiband d − p model describing a IrO4 layer (such as realized in Ba2IrO4) where all 34 orbitals per unit cell are partly occupied, i.e., t2g and eg orbitals at iridium and 2p orbitals at oxygen ions. The model takes into account anisotropic iridium-oxygen d − p and oxygen-oxygen p − p hopping processes, crystal-field splittings, spin-orbit coupling, and the on-site Coulomb interactions, both at iridium and at oxygen ions. We show that the predictions based on assumed idealized ionic configuration (with n0 = 5 + 4 × 6 = 29 electrons per IrO4 unit) do not explain well the independent ab initio data and the experimental data for Ba2IrO4. Instead we find that the total electron density in the d − p states is smaller, n = 29 − x < n0 (x > 0). When we fix x = 1, the predictions for the d − p model become more realistic and weakly insulating antiferromagnetic ground state with the moments lying within IrO2 planes along (110) direction is found, in agreement with experiment and ab initio data. We also show that: (i) holes delocalize over the oxygen orbitals and the electron density at iridium ions is enhanced, hence (ii) their eg orbitals are occupied by more than one electron and have to be included in the multiband d − p model describing iridates.

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Correlation effects in ferromagnetism of transition metals

Cited by 146 publications

References 30 publications

Wannier-function approach to spin excitations in solids

Wannier-function approach to spin excitations in solids

Ab initio calculations of magnetic structure and lattice dynamics of Fe/Pt multilayers

Multibandd−pmodel and self-doping in the electronic structure ofBa2IrO4

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