Site specific spin dynamics in BaFe2As2: tuning the ground state by orbital differentiation

Rosa, P. F. S.; Adriano, C.; Garitezi, T. M.; Grant, Ted; Fisk, Z.; Urbano, R. R.; Pagliuso, P. G.

doi:10.1038/srep06543

Cited by 8 publications

(13 citation statements)

References 38 publications

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“…Recent reported ESR measurements also revealed an increase of both anisotropy and localization of the Fe 3d bands at the FeAs plane in Eu 1−x Ba x Fe 2 As 2 with increasing x content 29,30 . Moreover, ESR data also pointed to a similar density of states for both under and overdoped Ba 1−x Eu x Fe 2 As 2 compounds.…”

Section: Resultsmentioning

confidence: 83%

Quantum oscillations inEuFe2As2single crystals

et al. 2014

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Quantum oscillation measurements provide relevant information about the Fermi surface (FS) properties of strongly correlated metals. Here, we report on the Shubnikov-de Haas (SdH) effect via high-field resistivity measurements of EuFe2As2 (Eu122) and BaFe2As2 (Ba122) single crystals. Although both pnictide compounds are isovalent with similar effective masses and density of states at the Fermi level, our results reveal subtle changes in their fermiology. Remarkably, although the spin-density-wave (SDW) ordering temperature is higher in the Eu-rich end, Eu122 displays a much more isotropic and 3D-like FS when compared with Ba122, in agreement with band structure calculations. Our experimental results suggest an anisotropic contribution of the Fe 3d orbitals to the FS in Ba122. We speculate that this orbital differentiation may be responsible for the suppression of the SDW phase in the FeAs-based compounds.

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Section: Resultsmentioning

confidence: 83%

Quantum oscillations inEuFe2As2single crystals

et al. 2014

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“…Small variations of γ across different compositions would not alter our main conclusions, as we discuss below. Moreover, the nearly constant ESR g-shift value found for the various ESR probes as a function of different chemical substitutions in Ba122 compounds is a strong evidence that the density of states at the Fermi level is nearly the same for pure Ba122 and for all studied compounds [13]. The choice of T c,0 = 26 K is a more subtle issue.…”

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confidence: 89%

“…Besides revealing the presence of localized moments, ESR also allows us to extract the averaged squared exchange coupling J 2 (q) between the localized moments and the conduction electrons from the linear increase of the linewidth with temperature (Korringa behavior) (see Table I) [12,13,15,31,37,38]. In a general approach for single-band metals, the thermal broadening b of the ESR linewidth ∆H 1/T 1 is the linear well-known Korringa relaxation defined as [32].…”

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“…We note that the detailed analysis of the ESR data confronted with Eu-substituted BaFe 2− x M x As 2 ( M = Co, Ni, Cu, Mn, and Ru) requires further technical discussion. Therefore, it will be the focus of a separated report 13 15 .…”

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“…1 and obtain the simplified expression: with Δ T c = T c − T c ,0 . The value for η ( E F ) is extracted from the linear coefficient of the low-temperature specific heat γ , yielding η ( E F ) = 3.34 states/eV.spin.FU for one mole, which is the same for all compounds 2 13 . Small variations of γ across different compositions would not alter our main conclusions, as we discuss below.…”

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Possible unconventional superconductivity in substituted BaFe2As2 revealed by magnetic pair-breaking studies

Rosa

Adriano

Garitezi

et al. 2014

Sci Rep

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The possible existence of a sign-changing gap symmetry in BaFe2As2-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe1.9M0.1As2 (M = Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.

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The role of magnetic excitations in magnetoresistance and Hall effect of slightly TM-substituted BaFe2As2 compounds (TM = Mn, Cu, Ni)

Peña

Piva

Jesus

et al. 2016

Physica C: Superconductivity and its Applications

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We report on electrical resistivity, magnetoresistance (MR) and Hall effect measurements in four non-superconducting BaFe2−xTMxAs2 (TM = Mn, Cu and Ni) single crystals with small values of the chemical substitution x. The spin density wave (SDW) ordering that occurs in these systems at temperatures T ∼ (120 -140) K, in close vicinity to a tetragonal/orthorhombic transition, produces significant modifications in their magneto-transport properties. While in the magnetically ordered phase the MR is positive and its magnitude increases with decreasing temperatures, in the paramagnetic regime the MR becomes vanishingly small. Above the spin density wave transition temperature (TSDW) the Hall coefficient RH is negative, small and weakly temperature dependent, but a remarkable change of slope occurs in the RH versus T curves at T = TSDW. The Hall coefficient amplitude, while remaining negative, increases steadily and significantly as the temperature is decreased below TSDW and down to T = 20 K. The qualitative behavior of both MR and Hall coefficient is weakly dependent on the chemical substitution in the studied limit. The experiments provide strong evidence that scattering of charge carriers by magnetic excitations has to be taken into account to explain the behavior of the resistivity, magnetoresistance and Hall effect in the ordered phase of the studied compounds. Effects of multiple band conduction also must be considered for a complete interpretation of the results.

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Site specific spin dynamics in BaFe2As2: tuning the ground state by orbital differentiation

Cited by 8 publications

References 38 publications

Quantum oscillations inEuFe2As2single crystals

Quantum oscillations inEuFe2As2single crystals

Possible unconventional superconductivity in substituted BaFe2As2 revealed by magnetic pair-breaking studies

The role of magnetic excitations in magnetoresistance and Hall effect of slightly TM-substituted BaFe2As2 compounds (TM = Mn, Cu, Ni)

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