Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity

Inosov, D. S.

doi:10.1016/j.crhy.2015.03.001

Cited by 100 publications

(105 citation statements)

References 405 publications

(583 reference statements)

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“…such as neutron scattering [10][11][12][13][14] and / or X-Ray Scattering [15,16]. Neutron scattering experiments confirmed the presence of sizable magnetic moments in Fe pnictides (on the order of ≈ 1 µ B ) [2,3,10] with few exceptions, such as NaFeAs that shows lower ordered magnetic moment [2,3].…”

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confidence: 73%

Presence of magnetic excitations in SmFeAsO

Pelliciari

Dantz

Huang

et al. 2016

Applied Physics Letters

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We measured dispersive spin excitations in SmFeAsO, parent compound of SmFeAsO 1-x F x one of the highest temperature superconductors of Fe pnictides (T C ≈55 K). We determine the magnetic excitations to disperse with a bandwidth energy of ca 170 meV at (0.47, 0) and (0.34, 0.34), which merges into the elastic line approaching the Γ point. Comparing our results with other parent Fe pnictides, we show the importance of structural parameters for the magnetic excitation spectrum, with small modifications of the tetrahedron angles and As height strongly affecting the magnetism.

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mentioning

confidence: 73%

Presence of magnetic excitations in SmFeAsO

Pelliciari

Dantz

Huang

et al. 2016

Applied Physics Letters

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“…Since magnetism may be responsible for many of the anomalous transport properties and origin of high-T c superconductivity in these materials 6 , previous efforts focused on understanding the evolution of magnetism as superconductivity is induced by electron or hole-doping to their AF parent compounds 3,[7][8][9] . In the case of copper oxides, spin excitations in hole-doped superconductors are marked by an hourglass-like dispersion 3 and a neutron spin resonance coupled with superconductivity 2 .…”

Section: (A)]mentioning

confidence: 99%

“…4,5 is their close proximity to a static antiferomagnetic (AF) ordered parent compound [6][7][8][9] . Since magnetism may be responsible for many of the anomalous transport properties and origin of high-T c superconductivity in these materials 6 , previous efforts focused on understanding the evolution of magnetism as superconductivity is induced by electron or hole-doping to their AF parent compounds 3,[7][8][9] .…”

Section: (A)]mentioning

confidence: 99%

Electron doping evolution of the magnetic excitations inNaFe1−xCoxAs

et al. 2016

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We use time-of-flight (ToF) inelastic neutron scattering (INS) spectroscopy to investigate the doping dependence of magnetic excitations across the phase diagram of NaFe1−xCoxAs with x = 0, 0.0175, 0.0215, 0.05, and 0.11. The effect of electron-doping by partially substituting Fe by Co is to form resonances that couple with superconductivity, broaden and suppress low energy (E ≤ 80 meV) spin excitations compared with spin waves in undoped NaFeAs. However, high energy (E > 80 meV) spin excitations are weakly Co-doping dependent. Integration of the local spin dynamic susceptibility χ ′′ (ω) of NaFe1−xCoxAs reveals a total fluctuating moment of 3.6 µ 2 B /Fe and a small but systematic reduction with electron doping. The presence of a large spin gap in the Cooverdoped nonsuperconducting NaFe0.89Co0.11As suggests that Fermi surface nesting is responsible for low-energy spin excitations. These results parallel Ni-doping evolution of spin excitations in BaFe2−xNixAs2 in spite of the differences in crystal structures and Fermi surface evolution in these two families of iron pnictides, thus confirming the notion that low-energy spin excitations coupling with itinerant electrons are important for superconductivity, while weakly doping dependent highenergy spin excitations result from localized moments.

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“…The observation of neutron spin resonance within a broad range of materials, in particular high-T c cuprates [1], iron pnictides [2,3], and heavy-fermion superconductors [4][5][6], is recognized as an indicator of unconventional superconductivity. It was shown that sign-changing gap symmetry can lead to the existence of resonance behavior [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Magnetic field dependence of the neutron spin resonance inCeB6

et al. 2016

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In zero magnetic field, the famous neutron spin resonance in the f-electron superconductor CeCoIn 5 is similar to the recently discovered exciton peak in the nonsuperconducting CeB 6 . A magnetic field splits the resonance in CeCoIn 5 into two components, indicating that it is a doublet. Here we employ inelastic neutron scattering (INS) to scrutinize the field dependence of spin fluctuations in CeB 6 . The exciton shows a markedly different behavior without any field splitting. Instead, we observe a second field-induced magnon whose energy increases with field. At the ferromagnetic zone center, however, we find only a single mode with a nonmonotonic field dependence. At low fields, it is initially suppressed to zero together with the antiferromagnetic order parameter, but then reappears at higher fields inside the hidden-order phase, following the energy of an electron spin resonance (ESR). This is a unique example of a ferromagnetic resonance in a heavy-fermion metal seen by both ESR and INS consistently over a broad range of magnetic fields. PACS numbers: 71.27.+a, 76.50.+g, 78.70.Nx, 76.30.Kg INTRODUCTIONThe observation of neutron spin resonance within a broad range of materials, in particular high-T c cuprates [1], iron pnictides [2,3], and heavy-fermion superconductors [4][5][6], is recognized as an indicator of unconventional superconductivity. It was shown that sign-changing gap symmetry can lead to the existence of resonance behavior [7][8][9][10]. Of particular interest are inelastic neutron scattering (INS) results obtained on CeCoIn 5 , where a sharp resonance peak was observed within the superconducting phase [5,[11][12][13]. At first glance similar peaks were found in the antiferromagnetic (AFM) superconductor UPd 2 Al 3 [14,15], as well as in the normal state of the heavy-fermion metal YbRh 2 Si 2 [16], where superconductivity was recently discovered below ∼ 2 mK [17]. Another striking example of a resonant mode is given by the well known nonsuperconducting heavyfermion antiferromagnet CeB 6 [18,19]. The microscopic origins of such resonant magnetic excitations persisting in f-electron systems either with or without superconductivity may well differ among materials and are still hotly debated.The application of an external magnetic field may help to unmask the differences between these various excitations. For instance, among f-electron compounds, a weak quasielastic signal gives rise to a field-induced ferromagnetic (FM) excitation in CeRu 2 Si 2 [20]. In YbRh 2 Si 2 , two incommensurate excitation branches merge into a commensurate FM resonance whose energy scales linearly with magnetic field [16], whereas in UPd 2 Al 3 the energy gap initially remains almost constant inside the superconducting phase, but starts following a monotonic linear dependence at higher magnetic fields [14]. The sharp resonance in CeCoIn 5 splits into a Zeeman doublet [11] rather than a theoretically predicted triplet [21], whereas in Ce 1−x La x B 6 the magnetic field reportedly leads to a crossover from an itinerant to ...

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Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity

Cited by 100 publications

References 405 publications

Presence of magnetic excitations in SmFeAsO

Presence of magnetic excitations in SmFeAsO

Electron doping evolution of the magnetic excitations inNaFe1−xCoxAs

Magnetic field dependence of the neutron spin resonance inCeB6

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