Spin fluctuations and superconductivity in powders of Fe_1+xTe_0.7Se_0.3 as a function of interstitial iron concentration

Abstract

Using neutron inelastic scattering, we investigate the role of interstitial iron on the low-energy spin fluctuations in powder samples of Fe_{1+x}Te_{0.7}Se_{0.3}. We demonstrate how combining the principle of detailed balance along with measurements at several temperatures allows us to subtract both temperature-independent and phonon backgrounds from S(Q,ω) to obtain purely magnetic scattering. For small values of interstitial iron (x=0.009(3)), the sample is superconducting (T_{c}=14 K) and displays a spin gap of 7 meV peaked in momentum at wave vector q_{0}=(π,π) consistent with single crystal results. On populating the interstitial iron sites, the superconducting volume fraction decreases and we observe a filling in of the low-energy magnetic fluctuations and a decrease of the characteristic wave vector of the magnetic fluctuations. For large concentrations of interstitial iron (x=0.048(2)) where the superconducting volume fraction is minimal, we observe the presence of gapless spin fluctuations at a wave vector of q_{0}=(π,0). We estimate the absolute total moment for the various samples and find that the amount of interstitial iron does not change the total magnetic spectral weight significantly, but rather has the effect of shifting the spectral weight in Q and energy. These results show that the superconducting and magnetic properties can be tuned by doping small amounts of iron and are suggestive that interstitial iron concentration is also a controlling dopant in the Fe_{1+x}Te_{1-y}Se_{y} phase diagram in addition to the Te/Se ratio.

(10 pages, 8 figures, to be published in Phys. Rev. B)

References in corpus (19)

• High-temperature superconductivity in iron-based materials
• Extreme Sensitivity of Superconductivity to Stoichiometry in FeSe (Fe1+dSe)
• Tellurium substitution effect on superconductivity of the alpha-phase Iron Selenide
• Incommensurate magnetic order in the alpha-Fe(Te,Se) superconductor systems
• First-order magnetic and structural phase transitions in Fe${}_{1+y}$Se${}_x$Te${}_{1-x}$
• Bulk Superconductivity at 14 K in Single Crystals of Fe1+yTexSe1-x
• From (pi, 0) magnetic order to superconductivity with (pi, pi) magnetic resonance in Fe1.02(Te1-xSex)
• Spin Gap and Resonance at the Nesting Wavevector in Superconducting FeSe0.4Te0.6
• Fermi surface topology and low-lying quasiparticle dynamics of parent Fe${}_{1+x}$Te/Se Superconductor by orbital-polarization resolved ARPES
• Density Functional Study of Excess Fe in Fe${}_{1+x}$Te: Magnetism and Doping
• Magnetic-crystallographic phase diagram of superconducting parent compound Fe${}_{1+x}$Te
• Spin waves in the $(\pi ,0)$ magnetically ordered iron chalcogenide Fe${}_{1.05}$Te
• Evidence for Unconventional Superconductivity in Arsenic-Free Iron-Based Superconductor FeSe : A ^77Se-NMR Study
• Interstitial Iron Controlled Superconductivity in Fe1+xTe0.7Se0.3
• First-order structural transition in the magnetically ordered phase of Fe1.13Te
• Continuous magnetic and structural phase transitions in Fe1+yTe
• Spin dynamics near the critical doping in weakly-superconducting underdoped YBa2Cu3O6.35 (Tc=18K)
• Neutron scattering from a coordination polymer quantum paramagnet
• Common origin of the two types of magnetic fluctuations in iron chalcogenides

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