Temperature dependent local atomic displacements in Ru substituted SmFe1−xRuxAsO0.85F0.15superconductors

Joseph, Boby; Iadecola, Antonella; Simonelli, Laura; Maugeri, Laura; Martinelli, A.; Palenzona, A.; Putti, M.; Saini, N. L.

doi:10.1088/0953-2048/26/6/065005

Cited by 19 publications

(24 citation statements)

References 39 publications

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“…There, spin dilution would cause static magnetism to vanish for x Ru ≈0.6, close to the theoretical value 0.593 [68]. However, there is significant evidence of a nonrandom distribution of Ru and microscopic phase separation in Ru-poor and Ru-rich regions [66,[69][70][71][72][73], suggesting that the global Ru content is not the relevant parameter to describe percolation. In Appendix B, we propose a simple model to reinterpret the NQR data of Sanna et al [66] by assuming a phase separation in Fe-rich and Ru-rich regions.…”

Section: B Doping-dependencesupporting

confidence: 56%

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Spatial competition of the ground states in 1111 iron pnictides

et al. 2016

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Using nuclear quadrupole resonance, the phase diagram of 1111 $R$FeAsO$_{1-x}$F$_x$ ($R$$=$La, Ce, Sm) iron pnictides is constructed as a function of the local charge distribution in the paramagnetic state, which features low-doping-like (LD-like) and high-doping-like (HD-like) regions. Compounds based on magnetic rare earths (Ce, Sm) display a unified behavior, and comparison with La-based compounds reveals the detrimental role of static iron $3d$ magnetism on superconductivity, as well as a qualitatively different evolution of the latter at high doping. It is found that the LD-like regions fully account for the orthorhombicity of the system, and are thus the origin of any static iron magnetism. Orthorhombicity and static magnetism are not hindered by superconductivity but limited by dilution effects, in agreement with 2D (respectively 3D) nearest-neighbor square lattice site percolation when the rare earth is nonmagnetic (respectively magnetic). The LD-like regions are not intrinsically supportive of superconductivity, on the contrary of the HD-like regions, as evidenced by the well-defined Uemura relation between the superconducting transition temperature and the superfluid density when accounting for the proximity effect. This leads us to propose a complete description of the interplay of ground states in 1111 pnictides, where nanoscopic regions compete to establish the ground state through suppression of superconductivity by static magnetism, and extension of superconductivity by proximity effect

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Section: B Doping-dependencesupporting

confidence: 56%

“…Following the observation of microscopic phase separation in Fe-rich and Ru-rich regions in 1111 samples where iron has been partially substituted with ruthenium [66,[69][70][71][72][73], we propose a simple model to reinterpret the data of Ref. 66.…”

Section: Discussionmentioning

confidence: 99%

Spatial competition of the ground states in 1111 iron pnictides

et al. 2016

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“…Here, the change in the σ 2 for Fe-Se bond is much smaller than that for the Fe-Fe bond. Earlier EXAFS studies on iron-based systems have pointed out such a change in the Fe-As correlations31, however, it turned out to be very small in the subsequent studies3233. The presence of this anomaly, indicating a local mode hardening by cooling across T c , is a clear evidence of some correlation between electron-lattice interactions and superconductivity.…”

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confidence: 90%

Temperature dependent local atomic displacements in ammonia intercalated iron selenide superconductor

Paris

Simonelli

Wakita

et al. 2016

Sci Rep

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Recently, ammonia-thermal reaction has been used for molecular intercalation in layered FeSe, resulting a new Lix(NH3)yFe2Se2 superconductor with Tc ~ 45 K. Here, we have used temperature dependent extended x-ray absorption fine structure (EXAFS) to investigate local atomic displacements in single crystals of this new superconductor. Using polarized EXAFS at Fe K-edge we have obtained direct information on the local Fe-Se and Fe-Fe bondlengths and corresponding mean square relative displacements (MSRD). We find that the Se-height in the intercalated system is lower than the one in the binary FeSe, suggesting compressed FeSe4 tetrahedron in the title system. Incidentally, there is hardly any effect of the intercalation on the bondlengths characteristics, revealed by the Einstein temperatures, that are similar to those found in the binary FeSe. Therefore, the molecular intercalation induces an effective compression and decouples the FeSe slabs. Furthermore, the results reveal an anomalous change in the atomic correlations across Tc, appearing as a clear decrease in the MSRD, indicating hardening of the local lattice mode. Similar response of the local lattice has been found in other families of superconductors, e.g., A15-type and cuprates superconductors. This observation suggests that local atomic correlations should have some direct correlation with the superconductivity.

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“…In cuprates, such anomalies were detected in several systems using extended x-ray absorption fine structure (EXAFS) spectroscopy studies [18,19] and neutron diffraction based atomic pair distribution function (PDF) analysis [20,21]. EXAFS [22][23][24][25][26][27][28][29] and x-ray PDF [30][31][32][33][34] studies were also yielded several important information on the FeSC, however, lack of high quality single crystals limited those studies. Here we report a systematic EXAFS study on the LaFe 1-…”

Section: Introductionmentioning

confidence: 99%

Temperature-Dependent As K-Edge EXAFS Studies of LaFe 1−x Co x AsO (x = 0.0 and 0.11) Single Crystals

Joseph

Ricci

Poccia

et al. 2016

J Supercond Nov Magn

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We report the experimental results of temperature dependent polarized As K-edge extended x-ray absorption fine structure (EXAFS) of LaFe 1-x Co x AsO (x=0.0 and 0.11) single-crystals. By aligning the Fe-As bond direction in the direction of the x-ray beam polarization we have been able to identify an anomaly in the Fe-As bond correlations at the tetragonal to orthorhombic transition at 150K, while previous investigations with standard unpolarized EXAFS of undoped LaFeAsO powder samples were not able to detect any such anomaly. Using our approach we have been able to identify in the superconducting doped sample, LaFe 0.89 Co 0.11 AsO, a broad anomaly around 60 K. The low temperature anomaly has good correlations with the temperature dependence of several properties like resistivity, magnetic susceptibility, linear thermal expansion, etc indicating the emergence of the dynamical oscillations of the Fe -As pairs.

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Temperature dependent local atomic displacements in Ru substituted SmFe_1−xRu_xAsO_0.85F_0.15superconductors

Cited by 19 publications

References 39 publications

Spatial competition of the ground states in 1111 iron pnictides

Spatial competition of the ground states in 1111 iron pnictides

Temperature dependent local atomic displacements in ammonia intercalated iron selenide superconductor

Temperature-Dependent As K-Edge EXAFS Studies of LaFe 1−x Co x AsO (x = 0.0 and 0.11) Single Crystals

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