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Dressed j eff-1/2 objects in mixed-valence lacunar spinel molybdates. Sci Rep 2023; 13:2411. [PMID: 36765082 PMCID: PMC9918447 DOI: 10.1038/s41598-023-28656-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 01/23/2023] [Indexed: 02/12/2023] Open
Abstract
The lacunar-spinel chalcogenides exhibit magnetic centers in the form of transition-metal tetrahedra. On the basis of density-functional computations, the electronic ground state of an Mo413+ tetrahedron has been postulated as single-configuration a12 e4 t25, where a1, e, and t2 are symmetry-adapted linear combinations of single-site Mo t2g atomic orbitals. Here we unveil the many-body tetramer wave-function: we show that sizable correlations yield a weight of only 62% for the a12 e4 t25 configuration. While spin-orbit coupling within the peculiar valence orbital manifold is still effective, the expectation value of the spin-orbit operator and the g factors deviate from figures describing nominal t5 jeff = 1/2 moments. As such, our data documents the dressing of a spin-orbit jeff = 1/2 object with intra-tetramer excitations. Our results on the internal degrees of freedom of these magnetic moments provide a solid theoretical starting point in addressing the intriguing phase transitions observed at low temperatures in these materials.
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Valldor M, Yadav R, Hozoi L, van den Brink J, Maljuk A, Werner J, Scaravaggi F, Wolter AUB, Büchner B. Swedenborgite
CaBa(Mn
2
Fe
2
)O
7
with Spin Ordering on a Geometrically Frustrated, Polar, Non‐centrosymmetric
S
= 5/2 Lattice. Z Anorg Allg Chem 2017. [DOI: 10.1002/zaac.201700292] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Martin Valldor
- Institute for Solid State Research Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Ravi Yadav
- Institute for Theoretical Solid State Physics Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Liviu Hozoi
- Institute for Theoretical Solid State Physics Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Andrey Maljuk
- Institute for Solid State Research Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Jochen Werner
- Institute for Solid State Research Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Francesco Scaravaggi
- Institute for Solid State Research Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Anja U. B. Wolter
- Institute for Solid State Research Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
| | - Bernd Büchner
- Institute for Solid State Research Leibniz Institute for Solid State and Materials Research, Dresden Helmholtzstraße 20 01069 Dresden Germany
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3
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Bogdanov NA, Bisogni V, Kraus R, Monney C, Zhou K, Schmitt T, Geck J, Mitrushchenkov AO, Stoll H, van den Brink J, Hozoi L. Orbital breathing effects in the computation of x-ray d-ion spectra in solids by ab initio wave-function-based methods. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:035502. [PMID: 27869641 DOI: 10.1088/1361-648x/29/3/035502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In existing theoretical approaches to core-level excitations of transition-metal ions in solids relaxation and polarization effects due to the inner core hole are often ignored or described phenomenologically. Here we set up an ab initio computational scheme that explicitly accounts for such physics in the calculation of x-ray absorption and resonant inelastic x-ray scattering spectra. Good agreement is found with experimental transition-metal L-edge data for the strongly correlated d 9 cuprate Li2CuO2, for which we determine the absolute scattering intensities. The newly developed methodology opens the way for the investigation of even more complex d n electronic structures of group VI B to VIII B correlated oxide compounds.
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Affiliation(s)
- Nikolay A Bogdanov
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany. Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
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4
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Bogdanov NA, Katukuri VM, Romhányi J, Yushankhai V, Kataev V, Büchner B, van den Brink J, Hozoi L. Orbital reconstruction in nonpolar tetravalent transition-metal oxide layers. Nat Commun 2015; 6:7306. [PMID: 26105992 PMCID: PMC4491190 DOI: 10.1038/ncomms8306] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 04/27/2015] [Indexed: 01/07/2023] Open
Abstract
A promising route to tailoring the electronic properties of quantum materials and devices rests on the idea of orbital engineering in multilayered oxide heterostructures. Here we show that the interplay of interlayer charge imbalance and ligand distortions provides a knob for tuning the sequence of electronic levels even in intrinsically stacked oxides. We resolve in this regard the d-level structure of layered Sr2IrO4 by electron spin resonance. While canonical ligand-field theory predicts g||-factors less than 2 for positive tetragonal distortions as present in Sr2IrO4, the experiment indicates g|| is greater than 2. This implies that the iridium d levels are inverted with respect to their normal ordering. State-of-the-art electronic-structure calculations confirm the level switching in Sr2IrO4, whereas we find them in Ba2IrO4 to be instead normally ordered. Given the nonpolar character of the metal-oxygen layers, our findings highlight the tetravalent transition-metal 214 oxides as ideal platforms to explore d-orbital reconstruction in the context of oxide electronics. The iridate compounds display interesting physical properties, including quasi-two-dimensional behaviour similar to cuprates. Bogdanov et al. explore the d-level structure of Sr2IrO4 using electron spin resonance measurements and detailed calculations and find it is inverted compared to its normal ordering
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Affiliation(s)
- Nikolay A Bogdanov
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Vamshi M Katukuri
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Judit Romhányi
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Viktor Yushankhai
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.,Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Russia
| | - Vladislav Kataev
- Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Bernd Büchner
- Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.,Department of Physics, Technical University Dresden, 01062 Dresden, Germany
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.,Department of Physics, Technical University Dresden, 01062 Dresden, Germany
| | - Liviu Hozoi
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
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5
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Katukuri VM, Roszeitis K, Yushankhai V, Mitrushchenkov A, Stoll H, van Veenendaal M, Fulde P, van den Brink J, Hozoi L. Electronic structure of low-dimensional 4d(5) oxides: interplay of ligand distortions, overall lattice anisotropy, and spin-orbit interactions. Inorg Chem 2014; 53:4833-9. [PMID: 24779549 DOI: 10.1021/ic402653f] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The electronic structure of the low-dimensional 4d(5) oxides Sr2RhO4 and Ca3CoRhO6 is herein investigated by embedded-cluster quantum chemistry calculations. A negative tetragonal-like t2g splitting is computed in Sr2RhO4 and a negative trigonal-like splitting is predicted for Ca3CoRhO6, in spite of having positive tetragonal distortions in the former material and cubic oxygen octahedra in the latter. Our findings bring to the foreground the role of longer-range crystalline anisotropy in generating noncubic potentials that compete with local distortions of the ligand cage, an issue not addressed in standard textbooks on crystal-field theory. We also show that sizable t2g(5)-t2g(4)eg(1) couplings via spin-orbit interactions produce in Sr2RhO4 ⟨Z⟩ = ⟨Σ(i)l(i)·s(i)⟩ ground-state expectation values significantly larger than 1, quite similar to theoretical and experimental data for 5d(5) spin-orbit-driven oxides such as Sr2IrO4. On the other hand, in Ca3CoRhO6, the ⟨Z⟩ values are lower because of larger t2g-eg splittings. Future X-ray magnetic circular dichroism experiments on these 4d oxides will constitute a direct test for the ⟨Z⟩ values that we predict here, the importance of many-body t2g-eg couplings mediated by spin-orbit interactions, and the role of low-symmetry fields associated with the extended surroundings.
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Affiliation(s)
- Vamshi M Katukuri
- Institute for Theoretical Solid State Physics, IFW Dresden , Helmholtzstrasse 20, 01069 Dresden, Germany
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6
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Bondino F, Barla A, Schmitt T, Strocov VN, Henry JY, Sanchez JP. Revealing the insulating gap in α'-NaV (2)O(5) with resonant inelastic x-ray scattering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:325402-5. [PMID: 22809788 DOI: 10.1088/0953-8984/24/32/325402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We measured the low energy excitation spectrum of α'-NaV (2)O(5) across its charge ordering and crystallographic phase transition with resonant inelastic x-ray scattering (RIXS) at the V L(3) edge. Exploiting the polarization dependence of the RIXS signal and the high resolution of the data, we reveal the excitation across the insulating gap at 1 eV and identify the excitations from occupied 3d(xy) bonding orbitals to unoccupied bonding 3d(xy) and 3d(yz)/3d(xz) orbitals. Furthermore we observe a progressive change of the electronic structure of α'-NaV (2)O(5) induced by soft x-ray irradiation, with the appearance of features characteristic of sodium deficient Na(x)V (2)O(5) (x < 1).
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Affiliation(s)
- F Bondino
- IOM CNR, Laboratorio TASC, S.S. 14, km 163.5, I-34012 Trieste, Italy.
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7
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Laubach S, Schmidt PC, Thissen A, Fernandez-Madrigal FJ, Wu QH, Jaegermann W, Klemm M, Horn S. Theoretical and experimental determination of the electronic structure of V2O5, reduced V2O5−xand sodium intercalated NaV2O5. Phys Chem Chem Phys 2007; 9:2564-76. [PMID: 17508089 DOI: 10.1039/b612489e] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work the electronic structure of V(2)O(5), reduced V(2)O(5-x) (V(16)O(39)) and sodium intercalated NaV(2)O(5) has been studied by both theoretical and experimental methods. Theoretical band structure calculations have been performed using density functional methods (DFT). We have investigated the electron density distribution of the valence states, the total density of states (total DOS) and the partial valence band density of states (PVBDOS). Experimentally, amorphous V(2)O(5) thin films have been prepared by physical vapour deposition (PVD) on freshly cleaved highly oriented pyrolytic graphite (HOPG) substrates at room temperature with an initial oxygen understoichiometry of about 4%, resulting in a net stoichiometry of V(2)O(4.8). These films have been intercalated by sodium using vacuum deposition with subsequent spontaneous intercalation (NaV(2)O(5)) at room temperature. Resonant V3p-V3d photoelectron spectroscopy (ResPES) experiments have been performed to determine the PVBDOS focusing on the calculation of occupation numbers and the determination of effective oxidation state, reflecting ionicity and covalency of the V-O bonds. Using X-ray absorption near edge spectra (XANES) an attempt is made to visualize the changes in the unoccupied DOS due to sodium intercalation. For comparison measurements on nearly stoichiometric V(2)O(5) single crystals have been performed. The experimental data for the freshly cleaved and only marginally reduced V(2)O(5) single crystals and the NaV(2)O(5) results are in good agreement with the calculated values. The ResPES results for V(2)O(4.8) agree in principle with the calculations, but the trends in the change of the ionicity differ between experiment and theory. Experimentally we find partly occupied V 3d states above the oxygen 2p-like states and a band gap between these and the unoccupied states. In theory one finds this occupation scheme assuming oxygen vacancies in V(2)O(5) and by performing a spin-polarized calculation of an antiferromagnetic ordered NaV(2)O(5.).
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Affiliation(s)
- Stefan Laubach
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstrasse 21, D-64287 Darmstadt, Germany
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8
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Bastardis R, Guihéry N, Suaud N, de Graaf C. Competition between double exchange and purely magnetic Heisenberg models in mixed valence systems: Application to half-doped manganites. J Chem Phys 2006; 125:194708. [PMID: 17129151 DOI: 10.1063/1.2375119] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A truncated Hubbard model is developed for the description of the electronic structure of odd-electron TM-L-TM units (TM=transition metal and L=ligand). The model variationally treats both the double exchange and purely magnetic Heisenberg configurations. This Hubbard model can either be mapped on a purely magnetic Heisenber model in which the bridging oxygen is also magnetic or on a double exchange model owing to the hybridization of the magnetic and ligand or bitals. The purely magnetic Heisenberg model is analytically solved in the general case of two metals (having n magnetic orbitals) bridged by a magnetic oxygen. The comparison of the analytical expressions of the Heisenberg energies to those of the double exchange model reveals that the two model spectra are identical except for one state which does not belong to the model space of the double exchange Hamiltonian. Consequently, the fitting of the model spectra to accurate ab initio spectra does not discriminate between the physically different models. These concepts are illustrated for the Mn-O-Mn unit (or Zener polaron) found in the half-doped manganite Pr(0.6)Ca(0.4)MnO3. It is shown that in the present case the projections of the ab initio ground state wave function onto both model spaces are almost identical provided that one uses properly localized orbitals, proving that the magnetic description of the Zener polaron and the double exchange viewpoint of the electronic structure are equally valid.
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Affiliation(s)
- Roland Bastardis
- Laboratoire de Physique Quantique, IRSAMC/UMR5626, Université Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse Cedex 4, France.
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9
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Abstract
The frozen local hole approximation (FLHA) is an adiabatic approximation which is aimed to simplify the correlation calculations of valence and conduction bands of solids and polymers or, more generally, of the ionization potentials and electron affinities of any large system. Within this approximation correlated local hole states (CLHSs) are explicitly generated by correlating local Hartree-Fock (HF) hole states, i.e., (N-1)-particle determinants in which the electron has been removed from a local occupied orbital. The hole orbital and its occupancy are kept frozen during these correlation calculations, implying a rather stringent configuration selection. Effective Hamilton matrix elements are then evaluated with the above CLHSs; diagonalization finally yields the desired correlation corrections for the cationic hole states. We compare and analyze the results of the FLHA with the results of a full multireference configuration interaction with single and double excitations calculation for two prototype model systems, (H2)n ladders and H-(Be)n-H chains. Excellent numerical agreement between the two approaches is found. Comparing the FLHA with a full correlation treatment in the framework of quasidegenerate variational perturbation theory reveals that the leading contributions in the two approaches are identical. In the same way it could be shown that a much less demanding self-consistent field (SCF) calculation around a frozen local hole fully recovers, up to first order, all the leading single excitation contributions. Thus, both the FLHA and the above SCF approximation are well justified and provide a very promising and efficient alternative to fully correlated wave-function-based treatments of the valence and conduction bands in extended systems.
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Affiliation(s)
- Elke Pahl
- Max-Planck-Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany.
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10
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de Graaf C, Hozoi L, Broer R. Magnetic interactions in calcium and sodium ladder vanadates. J Chem Phys 2004; 120:961-7. [PMID: 15267933 DOI: 10.1063/1.1630956] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Magnetic interactions in ladder vanadates are determined with quantum chemical computational schemes using the embedded cluster model approach to represent the material. The available experimental data for calcium vanadate is accurately reproduced and the nature of the interladder interaction is established to be ferromagnetic. An analysis of the main contributions to the magnetic couplings is presented and the role of the covalently bonded apex oxygen is elucidated. In the sodium vanadate, the ground state configuration of the rungs is V-3d1-O-2p5-V-3d1. We show that with this configuration good intrachain coupling constants are obtained for the high-temperature phase. The interchain coupling in NaV2O5 is predicted to be approximately 34 K, ferromagnetic in nature.
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Affiliation(s)
- C de Graaf
- Department of Physical and Inorganic Chemistry, Universitat Rovira i Virgili, Placa Imperial Tarraco 1, 43005 Tarragona, Spain.
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11
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Calzado CJ, Evangelisti S, Maynau D. Local Orbitals for the Truncation of Inactive Space: Application to Magnetic Systems. J Phys Chem A 2003. [DOI: 10.1021/jp034582t] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Carmen J. Calzado
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain, and Laboratoire de Physique Quantique, IRSAMC, Université Paul Sabatier, 31062 Toulouse-Cedex, France
| | - Stefano Evangelisti
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain, and Laboratoire de Physique Quantique, IRSAMC, Université Paul Sabatier, 31062 Toulouse-Cedex, France
| | - Daniel Maynau
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain, and Laboratoire de Physique Quantique, IRSAMC, Université Paul Sabatier, 31062 Toulouse-Cedex, France
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