First-principles study of the mixed oxide<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>α</mml:mi><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Fe</mml:mi><mml:mi mathvariant="normal">Cr</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Moore, Elaine

doi:10.1103/physrevb.76.195107

Cited by 53 publications

(41 citation statements)

References 33 publications

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“…According to literatures, 9,17,18 the absorption band at 1.8 eV corresponds to excitation of valence electrons at Cr t 2g and/ or O 2p states to the empty Fe t 2g * state. This picture is further supported by a recent theoretical study based on density functional theory (DFT) calculations with a Hubbard U-term, which concludes that the band-gap of CrFeO 3 is reduced to 1.9 eV.…”

Section: O 3 Solid-solution Filmsmentioning

confidence: 93%

“…6,7 It is a charge transfer (CT) insulator with a bandgap (E g ) of 2.1 eV between occupied O 2p state and empty Fe 3d upper Hubbard band. 6,8,9 a-Cr 2 O 3 is chosen as a counterpart material because of the absence of miscibility gap in binary phase diagram with a-Fe 2 O 3 . 10 It is known as a mixed CT and Mott-Hubbard insulator with E g ¼ 3.3 eV.…”

Section: O 3 Solid-solution Filmsmentioning

confidence: 99%

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Band-gap narrowing in α-(CrxFe1-x)2O3 solid-solution films

Mashiko

Oshima

Ohtomo

2011

Applied Physics Letters

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We report on structural and optical properties for the (0001)-oriented α-(CrxFe1-x)2O3 (0 ≤ x ≤ 1) epitaxial films prepared on c-sapphire substrates by using pulsed-laser deposition. Pure corundum phase with atomically flat surface was obtained in the entire composition range. Optical absorption spectra for the films with 0.2 < x < 0.9 showed a nearly constant band-gap (1.7 eV), which is narrower than those of α-Fe2O3 (2.1 eV) and α-Cr2O3 (3.0 eV). The result suggests that the band-gap narrowing arises from a type-II band alignment of these oxides and the fundamental band-gap lies between the Cr t2g and O 2p occupied states and the Fe t2g* empty state.

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Section: O 3 Solid-solution Filmsmentioning

confidence: 93%

Section: O 3 Solid-solution Filmsmentioning

confidence: 99%

Band-gap narrowing in α-(CrxFe1-x)2O3 solid-solution films

Mashiko

Oshima

Ohtomo

2011

Applied Physics Letters

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“…It is one of the few crystals whose band gap values are commonly used to gauge the level of correlation of the methods. [57] UHF often yields band gaps that are too large, [58] LSDA and SGGA on the other hand give very small or even null band gap. [59] B3LYP [57] gives a band gap of 3.2 eV comparable to the experimental value of 2.0 eV.…”

Section: Computational Detailsmentioning

confidence: 99%

“…[57] UHF often yields band gaps that are too large, [58] LSDA and SGGA on the other hand give very small or even null band gap. [59] B3LYP [57] gives a band gap of 3.2 eV comparable to the experimental value of 2.0 eV. We have calculated its HI atomic charges and spin-densities for α-Fe 2 O 3 with different Hamiltonians, namely UHF, PBE [39] and PBE0 [60] considering 8-6411G* and 8-411G* basis sets [50] for Fe and O, respectively.…”

Section: Computational Detailsmentioning

confidence: 99%

Hirshfeld-I charges in linear combination of atomic orbitals periodic calculations

et al. 2016

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Hirshfeld-I charges were implemented in the Crystal code, for periodic calculations with localized atomic basis sets. Some particular features of the present periodic implementation are detailed and discussed by means of selected illustrating examples. In these examples, the Hirshfeld-I charges are somewhere between the Bader and the Mulliken values and closer to the former. The implementation exploits heavily symmetry aspects and is shown to scale linearly with the unit cell dimension.Keywords Hirshfeld Iterative · Periodic calculations · Ab Initio · LCAO To A. Vela for his high human and scientific qualities.

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“…Indeed spin orbit interactions in the actinides can be thought of as an effective magnetic field -the main difference being that the effective magnetic field depends on the electron momentum. In addition, it has recently been shown that the importance of spin-orbit interactions varies in a systematic way as one moves across the actinides [8]. In particular, measurements of the branching ratios for 4d → 5f 5/2 and 4d → 5f 7/2 transitions in the actinides using TEM electron energy loss spectroscopy suggest that spin-orbit effects increase dramatically in importance as one moves from U to Pu and Am.…”

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confidence: 99%

Quantum criticality and the α/δ puzzle

Chapline

2009

Philosophical Magazine

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In an overview of the elemental actinides Np and Pu stand out because of their anomalously low melting temperatures and the variety of complex phase transitions that occur in these elements and their alloys as a result of relatively modest changes in temperature and pressure. In this paper we suggest a novel explanation based on an analogy between the evolution of the actinide ground state as a function of spin-orbit coupling and the behaviour of thin film superconductors in a magnetic field. The key point is that in "bad metals" spin-orbit interactions give rise to low energy monopolelike solitons with quantized spin currents, which play much the same role as Abrikosov vortices in thin film superconductors. In Np and α-Pu these solitons form an ordered solid, while in impurity stabilized δ-Pu they form a pair condensate. This provides a simple explanation for the heretofore unexplained phenomenology of α/δ transition. Near room temperature δ-Pu represents a novel form of condensed matter: a "Planckian metal" analogous to the quark-gluon plasma.At its onset the Manhattan Project was faced with the problem that the lattice structure and density of elemental Pu seemed to depend on how it was prepared. Despite the passage of 65 years an explanation of this puzzle has proved elusive. It has been suggested [1] that the underlying reason for this behaviour is that the ground state of elemental Pu lies near to a quantum critical point (QCP) of some kind. Indeed, the negative thermal expansion of pure δ-Pu is by itself suggestive of critical behaviour analogous to the Neel point of an antiferromagnet. Of course pointing out that as a function of atomic number the actinide ground state may have a quantum critical point doesn't explain why this happens. For a long time the conventional view has been that the unusual properties of elemental Pu and the α/δ transition in particular are somehow a consequence of a transition between itinerant f-electrons in the lower actinides and localized f-electrons in the higher actinides [2]. However it is now reasonably clear that the f-electrons in the pure elements do not become localized on an atomic scale as one moves from Np to Am. Indeed, studies of Pu/Am alloys [3] suggest that the f-electron bands do not change in any dramatic way as a function of Am concentration. On the other hand, as Harrison [4] has emphasized, the difference in the volume and free energy of the α and δ phases suggests that the f-electrons in the δ phase do not contribute to metallic binding. In the following we shall argue that this quasi-localization is very similar to the behaviour of electrons in disordered Type II thin film superconductors when the strength of an applied magnetic field exceeds a critical value, and the electrons form a "boson glass" [5].Actually there are hints that the unusual behaviour of Np/Pu may also be related to the physics of high temperature superconductors with no external field. For example, a plot showing the superconducting and magnetic ordering temperatures of the ...

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First-principles study of the mixed oxideα−FeCrO3

Abstract: 2We have investigated the electronic and magnetic properties of the mixed oxide α-

Cited by 53 publications

References 33 publications

Band-gap narrowing in α-(CrxFe1-x)2O3 solid-solution films

Band-gap narrowing in α-(CrxFe1-x)2O3 solid-solution films

Hirshfeld-I charges in linear combination of atomic orbitals periodic calculations

Quantum criticality and the α/δ puzzle

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