Anisotropic itinerant magnetism and spin fluctuations 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>: A neutron scattering study

Matan, K.; Morinaga, R.; Iida, Kazuki; Sato, Taku

doi:10.1103/physrevb.79.054526

Cited by 176 publications

(236 citation statements)

References 26 publications

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“…For the undoped materials the spin wave dispersion relations have been measured for the SrFe 2 As 2 [40], CaFe 2 As 2 [41,42], and BaFe 2 As 2 [43,44] systems, and the overall spin dynamics for the three systems are quite similar as shown in Table 3. These studies reveal that the spin dynamics are quite energetic, with a spin wave bandwidth ~0.2 eV as shown in Fig.…”

Section: Iron Spin Wavesmentioning

confidence: 80%

Neutron studies of the iron-based family of high TC magnetic superconductors

Lynn

Dai

2009

Physica C: Superconductivity

154

163

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We review neutron scattering investigations of the crystal structures, magnetic structures, and spin dynamics of the iron-based RFe(As,P)O (R=La, Ce, Pr, Nd), (Ba,Sr,Ca)Fe 2 As 2 , and Fe 1+x (Te-Se) systems. On cooling from room temperature all the undoped materials exhibit universal behavior, where a tetragonal-to-orthorhombic/monoclinic structural transition occurs, below which the systems become antiferromagnets. For the first two classes of materials the magnetic structure within the a-b plane consists of chains of parallel Fe spins that are coupled antiferromagnetically in the orthogonal direction, with an ordered moment typically less than one Bohr magneton. Hence these are itinerant electron magnets, with a spin structure that is consistent with Fermi-surface nesting and a very energetic spin wave bandwidth ~0.2 eV. With doping, the structural and magnetic transitions are suppressed in favor of superconductivity, with superconducting transition temperatures up to ≈55 K. Magnetic correlations are observed in the superconducting regime, with a magnetic resonance that follows the superconducting order parameter just like the cuprates. The rare-earth moments order antiferromagnetically at low T like 'conventional' magnetic-superconductors, while the Ce crystal field linewidths are affected when superconductivity sets in. The application of pressure in CaFe 2 As 2 transforms the system from a magnetically ordered orthorhombic material to a 'collapsed' non-magnetic tetragonal system. Tetragonal Fe 1+x Te transforms to a low T monoclinic structure at small x that changes to orthorhombic at larger x, which is accompanied by a crossover from commensurate to incommensurate magnetic order.Se doping suppresses the magnetic order, while incommensurate magnetic correlations are observed in the superconducting regime.

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Section: Iron Spin Wavesmentioning

confidence: 80%

Neutron studies of the iron-based family of high TC magnetic superconductors

Lynn

Dai

2009

Physica C: Superconductivity

154

163

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“…For a spin Hamiltonian, one can starts with a Heisenberg model where the energy of spin waves depends only on the relative orientation of neighboring spins. In the initial neutron scattering experiments on low-energy spin waves in SrFe 2 As 2 (Zhao et al, 2008a) (Matan et al, 2009), a spin gap due to magnetic iron anisotropy was identified. In addition, the low-energy spin waves were described by either a local moment Heisenberg Hamiltonian Zhao et al, 2008a) or the spin excitation continuum from itinerant electrons (Diallo et al, 2009;Matan et al, 2009).…”

Section: A Spin Waves In the Parent Compounds Of Iron-based Superconmentioning

confidence: 99%

Antiferromagnetic order and spin dynamics in iron-based superconductors

2015

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High-transition temperature (high-Tc) superconductivity in the iron pnictides/chalcogenides emerges from the suppression of the static antiferromagnetic order in their parent compounds, similar to copper oxides superconductors. This raises a fundamental question concerning the role of magnetism in the superconductivity of these materials. Neutron scattering, a powerful probe to study the magnetic order and spin dynamics, plays an essential role in determining the relationship between magnetism and superconductivity in high-Tc superconductors. The rapid development of modern neutron time-of-flight spectrometers allows a direct determination of the spin dynamical properties of iron-based superconductors throughout the entire Brillouin zone. In this review, we present an overview of the neutron scattering results on iron-based superconductors, focusing on the evolution of spin excitation spectra as a function of electron/hole-doping and isoelectronic substitution. We compare spin dynamical properties of iron-based superconductors with those of copper oxide and heavy fermion superconductors, and discuss the common features of spin excitations in these three families of unconventional superconductors and their relationship with superconductivity.

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“…30,[35][36][37] Instead, the methodology described in Reference 20 was employed. Critical temperatures were determined by comparing linear fits of the order parameter immediately before and after the transition.…”

Section: W E I G H T E D P H a S E F R A C T I O Nmentioning

confidence: 99%

Observation of the magnetic C4 phase in Ca1−xNaxFe2As2

et al. 2017

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Since its discovery in 2014 the magnetic tetragonal C4 phase has been identified in a growing number of hole-doped '122' Fe-based superconducting compounds. Exhibiting a unique double-Q magnetic structure and a strong competition with both superconducting and magnetic order parameters, the C4 phase and the conditions of its formation are of significant interest to understanding the fundamental mechanisms in these materials. Particularly, separating the importance of direct changes to the relative size of hole and electron pockets at the Fermi surface (achieved via charge doping) from the role of structural changes due to differences of ionic radii of dopants is useful to determine the underlying parameter which causes the C4 instability. Here, we report the discovery of the C4 phase in a fourth member of the hole-doped '122' materials Ca1−xNaxFe2As2 (0.20 ≤ x ≤ 0.50) as determined from neutron and X-ray powder diffraction studies. The maximum of the C4 dome is observed at x = 0.44 with a re-entrant temperature Tr= 52K and an extent of ∆x ∼ 0.07 in composition. It is observed that for a range of compositions within the C4 dome (0.40 ≤ x ≤ 0.42) there is a second re-entrance (Tr 2 < Tr) where the AFM-C2 phase is recovered -a feature previously only seen in Ba1−xKxFe2As2. A phase diagram is presented for Ca1−xNaxFe2As2 and compared to the other Na + -doped '122's' -A1−xNaxFe2As2 with A = Ba, Sr and Ca. The structural parameters for these three systems are compared and the importance of the 'chemical pressure' due to changing the A-site ion (A = Ba, Sr, Ca) is discussed.

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Anisotropic itinerant magnetism and spin fluctuations inBaFe2As2: A neutron scattering study

Cited by 176 publications

References 26 publications

Neutron studies of the iron-based family of high TC magnetic superconductors

Neutron studies of the iron-based family of high TC magnetic superconductors

Antiferromagnetic order and spin dynamics in iron-based superconductors

Observation of the magnetic C4 phase in Ca1−xNaxFe2As2

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