<i>Ab initio</i>lattice dynamics simulations and inelastic neutron scattering spectra for studying phonons in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>BaFe</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mtext>As</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>: Effect of structural phase transition, structural relaxation, and magnetic ordering

Zbiri, Mohamed; Schober, H.; Johnson, Mark R.; Rols, S.; Mittal, R.; Su, Yixi; Rotter, Marriane; Johrendt, Dirk

doi:10.1103/physrevb.79.064511

Cited by 75 publications

(100 citation statements)

References 29 publications

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“…An improvement is also observed for the Fe-As stretching modes. This is a clear signature of a magnetostructural correlation which affects phonon dynamics, and could indicate a selective spin-phonon coupling as recently suggested [27]. The situation is similar in the CaFe 2 As 2 and SrFe 2 As 2 cases shown in Figure 5, where magnetism improves the agreement.…”

Section: Effect Of Magnetic Ordering On Phonon Spectrasupporting

confidence: 80%

“…For a closely related topic to the presently reported one, ab-initio calculations for BaFe 2 As 2 show evidence for a selective coupling of electronic and spin degrees of freedom with phonons [27]. Furthermore, the measurement of the phonon density of states for the Ca 1111 CaFe 1−x Co x AsF (x = 0, 0.06, 0.12) indicates [28] that stronger spin-phonon interactions play an important role for the emergence of superconductivity in these compounds.…”

Section: Introductionmentioning

confidence: 63%

“…Structural analysis from x-ray powder diffraction indicates that the SrFe 2 As 2 and SrFeAsF samples contain about 1% of FeAs as an impurity phase. The inelastic neutron scattering experiments were performed using the IN4C and IN6 time of flight spectrometers at the Institut Laue Langevin (ILL), France as in our previous works [27,28,29]. Measurements were made on about 10 grams of polycrystalline samples.…”

Section: Experimental Details Of the Phonon Measurements Of Srfe 2 Asmentioning

confidence: 99%

“…The experimental phonon data for BaFe 2 As 2 , CaFe 2 As 2 are taken from Refs. [27] and [29], respectively. All the phonon spectra are normalized to unity.…”

Section: Effect Of Magnetic Ordering On Phonon Spectramentioning

confidence: 99%

“…The experimental phonon data for BaFe 2 As 2 are taken from Ref. [27]. spectra show pronounced differences in the full spectral range (Figure 6).…”

Section: Effect Of Magnetic Ordering On Phonon Spectramentioning

confidence: 99%

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Magnetic lattice dynamics of the oxygen-free FeAs pnictides: how sensitive are phonons to magnetic ordering?

Zbiri

Mittal

Rols

et al. 2010

J. Phys.: Condens. Matter

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Abstract. To shed light on the role of magnetism on the superconducting mechanism of the oxygen-free FeAs pnictides, we investigate the effect of magnetic ordering on phonon dynamics in the low-temperature orthorhombic parent compounds, which present a spin-density wave. The study covers both the 122 (AFe 2 As 2 ; A=Ca, Sr, Ba) and 1111 (AFeAsF; A=Ca, Sr) phases. We extend our recent work on the Ca (122 and 1111) and Ba (122) cases by treating computationally and experimentally the 122 and 1111 Sr compounds. The effect of magnetic ordering is investigated through detailed non-magnetic and magnetic lattice dynamical calculations. The comparison of the experimental and calculated phonon spectra shows that the magnetic interactions/ordering have to be included in order to reproduce well the measured density of states. This highlights a spin-correlated phonon behavior which is more pronounced than the apparently weak electron-phonon coupling estimated in these materials. Furthermore, there is no noticeable difference between phonon spectra of the 122 Ba and Sr, whereas there are substantial differences when comparing these to CaFe 2 As 2 originating from different aspects of structure and bonding.

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Section: Effect Of Magnetic Ordering On Phonon Spectrasupporting

confidence: 80%

Section: Introductionmentioning

confidence: 63%

Section: Experimental Details Of the Phonon Measurements Of Srfe 2 Asmentioning

confidence: 99%

“…The experimental phonon data for BaFe 2 As 2 , CaFe 2 As 2 are taken from Refs. [27] and [29], respectively. All the phonon spectra are normalized to unity.…”

Section: Effect Of Magnetic Ordering On Phonon Spectramentioning

confidence: 99%

“…The experimental phonon data for BaFe 2 As 2 are taken from Ref. [27]. spectra show pronounced differences in the full spectral range (Figure 6).…”

Section: Effect Of Magnetic Ordering On Phonon Spectramentioning

confidence: 99%

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Magnetic lattice dynamics of the oxygen-free FeAs pnictides: how sensitive are phonons to magnetic ordering?

Zbiri

Mittal

Rols

et al. 2010

J. Phys.: Condens. Matter

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On the multi‐orbital band structure and itinerant magnetism of iron‐based superconductors

2011

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This paper explains the multi-orbital band structures and itinerant magnetism of the iron-pnictide and chalcogenide superconductors. We first describe the generic band structure of a single, isolated FeAs layer. Use of its Abelian glide-mirror group allows us to reduce the primitive cell to one FeAs unit. For the lines and points of high symmetry in the corresponding large, square Brillouin zone, we specify how the one-electron Hamiltonian factorizes. From density-functional theory, and for the observed structure of LaOFeAs, we generate the set of eight Fe d and As p localized Wannier functions and their tight-binding (TB) Hamiltonian, h (k). For comparison, we generate the set of five Fe d Wannier orbitals. The topology of the bands, i.e. allowed and avoided crossings, specifically the origin of the d 6 pseudogap, is discussed, and the role of the As p orbitals and the elongation of the FeAs4 tetrahedron emphasized. We then couple the layers, mainly via interlayer hopping between As pz orbitals, and give the formalism for simple tetragonal and body-centered tetragonal (bct) stackings. This allows us to explain the material-specific 3D band structures, in particular the complicated ones of bct BaFe2As2 and CaFe2As2 whose interlayer hoppings are large. Due to the high symmetry, several level inversions take place as functions of kz or pressure, and linear band dispersions (Dirac cones) are found at many places. The underlying symmetry elements are, however, easily broken by phonons or impurities, for instance, so that the Dirac points are not protected. Nor are they pinned to the Fermi level because the Fermi surface has several sheets. From the paramagnetic TB Hamiltonian, we form the band structures for spin spirals with wavevector q by coupling h (k) and h (k + q) . The band structure for stripe order is studied in detail as a function of the exchange potential, ∆, or moment, m, using Stoner theory. Gapping of the Fermi surface (FS) for small ∆ requires matching of FS dimensions (nesting) and d-orbital characters. The interplay between pd hybridization and magnetism is discussed using simple 4 × 4 Hamiltonians. The origin of the propeller-shaped Fermi surface is explained in detail. Finally, we express the magnetic energy as the sum over band-structure energies and this enables us to understand to what extent the magnetic energies might be described by a Heisenberg Hamiltonian, and to address the much discussed interplay between the magnetic moment and the elongation of the FeAs4 tetrahedron.Copyright line will be provided by the publisher ForewordThis paper is dedicated to Manuel Cardona, on the occasion of his 75th birthday. Manuel Cardona is worldfamous not only for being an outstanding and creative experimentalist, but also for having deep theoretical insights, in particular into the band structures of solids. His book [1] with Peter Yu on Fundamentals of Semiconductors, now a classic of solid-state physics, devotes a large part to the explanation of theory in simple, accessible language. For our contribu...

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Magnetic excitation and thermodynamics of BaFe₂As₂

Wang

Shang

Chen

et al. 2010

Int J of Quantum Chemistry

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Magnetic excitation of the iron-based superconductor parent compound BaFe 2 As 2 at finite temperature are addressed with a first-principles formulation of the Helmholtz energy, which can account for the finite temperature mixture of many magnetic configurations. We find that it is the spin exchange coupling in the interplane c direction that dictates the spin density wave ordering. We have also quantitatively predicted the pressure dependence of the spin density wave ordering temperature, the Schottky anomaly, and the temperature dependence of thermal populations of several low-energy spin configurations, all in agreement with available experimental data.

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Ab initiolattice dynamics simulations and inelastic neutron scattering spectra for studying phonons inBaFe2As2: Effect of structural phase transition, structural relaxation, and magnetic ordering

Cited by 75 publications

References 29 publications

Magnetic lattice dynamics of the oxygen-free FeAs pnictides: how sensitive are phonons to magnetic ordering?

Magnetic lattice dynamics of the oxygen-free FeAs pnictides: how sensitive are phonons to magnetic ordering?

On the multi‐orbital band structure and itinerant magnetism of iron‐based superconductors

Magnetic excitation and thermodynamics of BaFe₂As₂

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Ab initiolattice dynamics simulations and inelastic neutron scattering spectra for studying phonons inBaFe2As2: Effect of structural phase transition, structural relaxation, and magnetic ordering

Cited by 75 publications

References 29 publications

Magnetic lattice dynamics of the oxygen-free FeAs pnictides: how sensitive are phonons to magnetic ordering?

Magnetic lattice dynamics of the oxygen-free FeAs pnictides: how sensitive are phonons to magnetic ordering?

On the multi‐orbital band structure and itinerant magnetism of iron‐based superconductors

Magnetic excitation and thermodynamics of BaFe2As2

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Product

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Magnetic excitation and thermodynamics of BaFe₂As₂