Pressure and chemical substitution effects in the local atomic structure of BaFe2As2

Abstract

The effects of K and Co substitutions and quasi-hydrostatic applied pressure (P < 9 GPa) in the local atomic structure of BaFe2As2, Ba(Fe0.937Co0.063)2As2 and Ba0.85K0.15Fe2As2 superconductors were investigated by extended x-ray absorption fine structure (EXAFS) measurements in the As K absorption edge. The As-Fe bond length is found to be slightly reduced ( 0.01Å) by both Co and K substitutions, without any observable increment in the corresponding Debye Waller factor. Also, this bond is shown to be compressible (κ = 3.3(3) × 10 −3 GPa −1 ). The observed contractions of As-Fe bond under pressure and chemical substitutions are likely related with a reduction of the local Fe magnetic moments, and should be an important tuning parameter in the phase diagrams of the Fe-based superconductors.

Uniaxial versus hydrostatic pressure-induced phase transitions in CaFe2As2and BaFe2AsTomić1, Valentí2, Jeschke3 2012Phys. Rev. B

“…This is in very good agreement with the experimental estimate of B = 153 ± 3GPa for the collapsed tetragonal phase [10]. We also analyzed the Fe-As bond compressibility for P = 9 GPa (hydrostatic) and found κ = 3.5 × 10 −3 GPa −1 which is in excellent agreement with κ = 3.3 × 10 −3 GPa −1 obtained in an extended Xray absorption fine structure (EXAFS) experiment [26]. In Fig.…”

“…We expect that this overestimation affects mostly the values of P c . Comparison of our calculated Fe-As bond distances at different pressures with measured distances [26] shows good agreement. Also, available de Haas van Alphen measurements performed for CaFe 2 P 2 [25] agree well with our predicted Fermi surface shapes for CaFe 2 As 2 in the collapsed tetragonal phase.…”

“…In Fig. 4 we show the comparison of the measured pressure dependence of the Fe-As bond distances [26] with our results. Due to different temperatures (experiment is performed at room temperature, theory at T = 0) our distances are shorter by about 0.02Å (0.8%), but the overall agreement is good.…”

Evolution of Eu2+spin dynamics in Ba1−xEuxRosa1, Adriano2, Iwamoto3 et al. 2012Phys. Rev. BSelf Cite151151View full textAdd to dashboardCite

“…32 Recent EXAFS experiments reported that the Fe-As bonds in BaFe 2 As 2 are slightly smaller upon hydrostatic pressure, hole, and electron doping. 33 The increasing localization of the itinerant Fe d at the Fe sites claimed in this work for Ba 1−x Eu x Fe 2 As 2 is consistent with all previous experiments mentioned above and may help the understanding of the SDW phase suppression by doping in this class of materials. Now we turn our attention to the more diluted regime (x < 0.20).…”

Quantum oscillations inEuFe2As2single crystals

“…Previous EXAFS (Extended X-Ray Absorption Fine Structure) measurements on In-grown Ba122 single crystals revealed a decrease of the Fe-As distances as T SDW is suppressed by either chemical substitution (K and Co) or applied pressure 31 . In addition, DFT+DFMT calculations also predicted a decrease of the planar xy orbital contribution to the FS as the Fe-As distance is increased 15 .…”