Orbital Physics in Transition Metal Oxides: Magnetism and Optics

Horsch, Peter

doi:10.1002/9780470022184.hmm107

Cited by 9 publications

(18 citation statements)

References 226 publications

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“…Moreover, for the sake of fixing precisely Hund's coupling tensor elements J d µ,ν we use Table I from Ref. [36] and in addition we use an empiric formula C 4B for Racah parameters. With this Ansatz for a pure t 2g system J d H = 3B + C ≈ 7B and B = 0.1 eV [9].…”

Section: Setting the Hamiltonian Parameters A Previous Studies mentioning

confidence: 99%

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Charge-transfer model for the electronic structure of layered ruthenates

Rościszewski

Oleś

2015

Phys. Rev. B

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Motivated by the earlier experimental results and ab initio studies on the electronic structure of layered ruthenates (Sr2RuO4 and Ca2RuO4) we introduce and investigate the multiband d − p charge transfer model describing a single RuO4 layer, similar to the charge transfer model for a single CuO2 plane including apical oxygen orbitals in high Tc cuprates. The present model takes into account nearest-neighbor anisotropic ruthenium-oxygen d − p and oxygen-oxygen p − p hopping elements, crystal-field splittings and spin-orbit coupling. The intraorbital Coulomb repulsion and Hund's exchange are defined not only at ruthenium but also at oxygen ions. Our results demonstrate that the RuO4 layer cannot be regarded to be a pure ruthenium t2g system. We examine a different scenario in which ruthenium eg orbitals are partly occupied and highlight the significance of oxygen orbitals. We point out that the predictions of an idealized model based on ionic configuration (with n0 = 4 + 4 × 6 = 28 electrons per RuO4 unit) do not agree with the experimental facts for Sr2RuO4 which support our finding that the electron number in the d − p states is significantly smaller. In fact, we find the electron occupation of d and p orbitals for a single RuO4 unit n = 28 − x, being smaller by at least 1-1.5 electrons from that in the ionic model and corresponding to self-doping with x 1.5.

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Section: Setting the Hamiltonian Parameters A Previous Studies mentioning

confidence: 99%

“…This determines the J d µ,ν elements when e g levels are not empty (using again the entries from Table I in Ref. [36]). …”

Section: Setting the Hamiltonian Parameters A Previous Studies mentioning

confidence: 99%

Charge-transfer model for the electronic structure of layered ruthenates

Rościszewski

Oleś

2015

Phys. Rev. B

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“…For the sake of fixing precisely Hund's coupling tensor elements J d,µν we use Table I from Ref. [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].…”

Section: The Hamiltonian Parametersmentioning

confidence: 99%

“…The J d,µν elements concerning e g orbitals are finite and fixed again using the entries from Table I in Ref. [31].…”

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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“…where J µν is the tensor of on-site interorbital exchange elements for 3d orbitals which can be expressed using Racah parameters B and C [29,30] (see table 1 given by Horsch [29]). Note that each pair of different orbitals µ = ν is included twice in equation (8).…”

Section: The Effective Model For 3d Electronsmentioning

confidence: 99%

A possibility of high spin hole states in doped CoO₂layered systems

Rościszewski¹,

Oleś²

2013

J. Phys.: Condens. Matter

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Abstract. We introduce and investigate an effective five-band model for t 2g and e g electrons to describe doped cobalt oxides with Co 3+ and Co 4+ ions in two-dimensional CoO 2 triangular lattice layers, as in Na 1−x CoO 2 . The effective Hamiltonian includes anisotropic kinetic energy (due to both direct Co-Co and indirect Co-O-Co hoppings), on-site Coulomb interactions parameterized by intraorbital Hubbard repulsion U and full Hund's exchange tensor, crystal-field terms and Jahn-Teller static distortions. We study it using correlated wave functions on 6 × 6 clusters with periodic boundary conditions. The computations indicate low S = 0 spin to high S = 2 spin abrupt transition in the undoped systems when increasing strength of the crystal field, while intermediate S = 1 spins are not found. Surprisingly, for the investigated realistic Hamiltonian parameters describing low spin states in CoO 2 planes, doping generates high S = 5 2 spins at Co 4+ ions that are pairwise bound into singlets, seen here as pairs of up and down spins. It is found that such singlet pairs self-organize at higher doping into lines of spins with coexisting antiferromagnetic and ferromagnetic bonds, forming stripe-like structures. The ground states are insulating within the investigated range of doping because computed HOMO-LUMO gaps are never small enough.

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Orbital Physics in Transition Metal Oxides: Magnetism and Optics

Cited by 9 publications

References 226 publications

Charge-transfer model for the electronic structure of layered ruthenates

Charge-transfer model for the electronic structure of layered ruthenates

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

A possibility of high spin hole states in doped CoO₂layered systems

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Orbital Physics in Transition Metal Oxides: Magnetism and Optics

Cited by 9 publications

References 226 publications

Charge-transfer model for the electronic structure of layered ruthenates

Charge-transfer model for the electronic structure of layered ruthenates

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

A possibility of high spin hole states in doped CoO2layered systems

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A possibility of high spin hole states in doped CoO₂layered systems