Paramagnetic resonance and near-infrared optical absorption of SrTiO<sub>3</sub>:Ir<sup>4+</sup>

Schirmer, O. F.; Forster, A.; Hesse, H.; Wöhlecke, M.; Kapphan, S.

doi:10.1088/0022-3719/17/7/024

Cited by 42 publications

(26 citation statements)

References 16 publications

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“…The spin couplings obtained are reasonable for the 90 • -exchange bonds (as expected [8,11], they are much smaller than in 180 • -bond perovskites [13,14]). The magnitude of Van Vleck term also agrees with our estimate χ 0 ≃ 8 3λ µ 2 B N A ≃ 0.2 × 10 −3 cm 3 /mol for Ir 4+ ion, considering spin-orbit coupling λ ≃ 0.4 eV [13,15,30].…”

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Zigzag Magnetic Order in the Iridium OxideNa2IrO3

2013

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We explore the phase diagram of spin-orbit Mott insulators on a honeycomb lattice, within the Kitaev-Heisenberg model extended to its full parameter space. Zigzag-type magnetic order is found to occupy a large part of the phase diagram of the model, and its physical origin is explained as due to interorbital t2g − eg hopping. Magnetic susceptibility and spin wave spectra are calculated and compared to the experimental data, obtaining thereby the spin coupling constants in Na2IrO3 and Li2IrO3.

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confidence: 90%

“…This approximation is valid as long as ∆ is much smaller than spin-orbit coupling λ ≃ 0.4 eV [13,15,30] and seems to be justified, since the recent ab-initio calculations [20] suggest that ∆ ≃ 75 meV only [31].…”

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Zigzag Magnetic Order in the Iridium OxideNa2IrO3

2013

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“…4+ (5d 5 )-doped SrTiO 3 were examined by means of the EPR technique, and the spin Hamiltonian parameters, g factors (g || and g ⊥ ) and the hyperfine structure constants A || and A ⊥ for the tetragonal nd 5 (n = 3 and 5) centers were measured at 4.2 and 77 K [8,9]. Since SrTiO 3 is known to undergo a structural phase transition at 105 K, information about local structures and properties around impurities would be helpful in the understanding of the properties of this material with certain dopants.…”

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confidence: 99%

“…Since SrTiO 3 is known to undergo a structural phase transition at 105 K, information about local structures and properties around impurities would be helpful in the understanding of the properties of this material with certain dopants. The authors gave some explanations of the observed EPR results, by considering the contributions from the crystal fields and the spin-orbit coupling interactions [8,9]. Nevertheless, the local structures (particularly the tetragonal distortions) around the impurity ions were not considered, nor were the structures correlated with the experimental spin Hamiltonian parameters.…”

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confidence: 99%

Theoretical studies of the spin Hamiltonian parameters for the tetragonal Co⁴⁺ and Ir⁴⁺ centers in SrTiO₃

Zhang

et al. 2008

Physica Status Solidi (b)

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The spin Hamiltonian parameters, g factors and the hyperfine structure constants for Co4+ (3d5) and Ir4+ (5d5) in SrTiO3 are theoretically studied from the formulas of these parameters for an n d5 (n = 3 and 5) ion in a tetragonally distorted octahedron with low spin S = 1/2. According to the theoretical analyses, the impurity–ligand bond lengths R ′‖ parallel to the C4 axis are found to be larger than the host values R‖ based on the phase transition rotation angles ϕ of the [TiO6]8– octahedron by the C4 axis at 4.2 and 77 K, respectively. The elongation of the ligand octahedra in the host may be enhanced in the impurity centers by the Jahn–Teller effect of the n d5 ions. The theoretical results based on the above local structures show good agreement with the experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…[7] Secondly, conduction electrons originate from Ir 5d bands, where a strong spin-orbit interaction is present. [8] Thirdly, related compounds A 2 Ir 2 O 7 (A = Y or rare earth metals) exhibit thermal metal-insulator transitions caused by a strong electron correlation effect. [9] Despite these intriguing features, there have been no reported studies using a single-crystalline sample.…”

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Mechanism of Enhanced Optical Second-Harmonic Generation in the Conducting Pyrochlore-TypePb2Ir2O7−xOxide Compound

et al. 2013

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The structural, electronic, and optical properties of pyrochlore-type Pb 2 Ir 2 O 6 O' 0.55 , which is a metal without spatial inversion symmetry at room temperature, were investigated. Structural analysis revealed that the structural distortion relevant to the breakdown of the inversion symmetry is dominated by the Pb-O' network but is very small in the Ir-O network. At the same time, gigantic second-harmonic generation signals were observed, which can only occur if the local environment of the Ir 5d electrons features broken inversion symmetry. First-principles electronic structure calculations reveal that the underlying mechanism for this phenomenon is the induction of the noncentrosymmetricity in the Ir 5d bands by the strong hybridization with O' 2p orbitals. Our results stimulate theoretical study of inversion-broken iridates, where exotic quantum states such as a topological insulator and Dirac semimetal are anticipated. PACS numbers: 61.66.Fn, 78.47.jh 1 Symmetry is a critical factor that controls the physical properties of a solid. Spatial inversion symmetry is one of the most important symmetries. The most common and well-studied systems without inversion symmetry are the ferroelectrics, where macroscopic polarization appears in an insulating state. Recently, conductive materials without inversion symmetry, which are known as "noncentrosymmetric metals" or "polar metals", have also attracted interest [1,2]. In contrast to ferroelectrics, noncentrosymmetric metals do not exhibit macroscopic polarization due to screening by conducting electrons; instead the state is characterized by a higher-rank tensor (e.g. piezo-electric tensor). The breakdown of inversion symmetry is considered to influence the transport properties. For example, it is theoretically predicted that the inverse Faraday effect can be induced by Rashba interaction. [1,3,4] However, there have been few experimental studies, because noncentrosymmetric metals are rare.There are several noncentrosymmetric metals in the pyrochlore-type transition-metal ox- In this Letter, we report the structural, electronic, and optical properties of singlecrystalline Pb 2 Ir 2 O 7−x with special attention given to the inversion symmetry. While the structural analysis shows that the inversion symmetry breaking is dominated by Pb-O' 2 bonds, the observed SHG signals, which mainly originate from the noncentrosymmetricity of the Ir 5d band, are strong. We demonstrate that this phenomena is caused by the large hybridization of Ir 5d and O' 2p orbitals, which is unique characteristics of Pb-containing pyrochlore-type oxides.Single crystals of Pb 2 Ir 2 O 7−x with sizes of 2 mm 3 were grown by the self-flux method.PbO and IrO 2 powders were mixed in a molar ratio of 9:1, heated to 1250• C, and then cooled to 950• C at a cooling rate of 5• C/h. Scanning electron microscopy/energy dispersive Xray analysis showed that the content ratio of Pb to Ir was 1.0. The oxygen deficiency was determined to be x = 0.45 by the thermogravimetric/differential thermal anal...

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Paramagnetic resonance and near-infrared optical absorption of SrTiO₃:Ir⁴⁺

Cited by 42 publications

References 16 publications

Zigzag Magnetic Order in the Iridium OxideNa2IrO3

Zigzag Magnetic Order in the Iridium OxideNa2IrO3

Theoretical studies of the spin Hamiltonian parameters for the tetragonal Co⁴⁺ and Ir⁴⁺ centers in SrTiO₃

Mechanism of Enhanced Optical Second-Harmonic Generation in the Conducting Pyrochlore-TypePb2Ir2O7−xOxide Compound

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Paramagnetic resonance and near-infrared optical absorption of SrTiO3:Ir4+

Cited by 42 publications

References 16 publications

Zigzag Magnetic Order in the Iridium OxideNa2IrO3

Zigzag Magnetic Order in the Iridium OxideNa2IrO3

Theoretical studies of the spin Hamiltonian parameters for the tetragonal Co4+ and Ir4+ centers in SrTiO3

Mechanism of Enhanced Optical Second-Harmonic Generation in the Conducting Pyrochlore-TypePb2Ir2O7−xOxide Compound

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Paramagnetic resonance and near-infrared optical absorption of SrTiO₃:Ir⁴⁺

Theoretical studies of the spin Hamiltonian parameters for the tetragonal Co⁴⁺ and Ir⁴⁺ centers in SrTiO₃