On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View

Mangelis, Panagiotis; Lei, Hechang; McDonnell, Marshall; Feygenson, Mikhail; Petrovic, Cedomir; Bozin, Emil; Lappas, Alexandros

doi:10.3390/condmat3030020

Title: On the Nanoscale Structure of K_xFe_2-yCh₂ (Ch = S, Se): A Neutron Pair Distribution Function View

Abstract

Comparative exploration of the nanometer-scale atomic structure of K_xFe_2-yCh₂ (Ch = S, Se) was performed using neutron total scattering-based atomic pair distribution function (PDF) analysis of 5 K powder diffraction data in relation to physical properties. Whereas K_xFe_2-ySe₂ is a superconductor with a transition temperature of about 32 K, the isostructural sulphide analogue is not, which instead displays a spin glass semiconducting behavior at low temperatures. The PDF analysis explores phase separated and disordered structural models as candidate descriptors of the low temperature data. For both materials, the nanoscale structure is well described by the iron (Fe)-vacancy-disordered K₂Fe_5-yCh₅ (I4/m) model containing excess Fe. An equally good description of the data is achieved by using a phase separated model comprised of I4/m vacancy-ordered and I4/mmm components. The I4/mmm component appears as a minority phase in the structure of both K_xFe_2-ySe₂ and K_xFe_2-yS₂, and with similar contribution, implying that the phase ratio is not a decisive factor influencing the lack of superconductivity in the latter. Comparison of structural parameters of the Fe-vacancy-disordered model indicates that the replacement of selenium (Se) by sulphur (S) results in an appreciable reduction in the Fe-Ch interatomic distances and anion heights, while simultaneously increasing the irregularity ofmore »« less

Authors:

Mangelis, Panagiotis ^[1]; Lei, Hechang ^[2]; McDonnell, Marshall ^[3]; Feygenson, Mikhail ^[3]; Petrovic, Cedomir ^[2]; Bozin, Emil ^[2];

^[1]

Inst. of Electronic Structure and Laser (IESL), Foundation for Research and Technology- Hellas (FORTH), Vassilika Vouton, Heraklion (Greece)
Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Scattering Division

Publication Date:: Tue Jul 03 00:00:00 EDT 2018

Research Org.:: Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:: 1459171

Report Number(s):: BNL-206809-2018-JAAM
Journal ID: ISSN 2410-3896; TRN: US1901547

Grant/Contract Number:: SC0012704

Resource Type:: Accepted Manuscript

Journal Name:: Condensed Matter

Additional Journal Information:: Journal Volume: 3; Journal Issue: 3; Journal ID: ISSN 2410-3896

Publisher:: MDPI

Country of Publication:: United States

Language:: English

Subject:: 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; neutron pair distribution function (PDF); intercalated iron superconductors; anion height; tetrahedron regularity

Citation Formats


                    Mangelis, Panagiotis, Lei, Hechang, McDonnell, Marshall, Feygenson, Mikhail, Petrovic, Cedomir, Bozin, Emil, and Lappas, Alexandros. On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View.  United States: N. p., 2018. 
Web.  doi:10.3390/condmat3030020.

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                    Mangelis, Panagiotis, Lei, Hechang, McDonnell, Marshall, Feygenson, Mikhail, Petrovic, Cedomir, Bozin, Emil, & Lappas, Alexandros. On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View.  United States.  https://doi.org/10.3390/condmat3030020

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                    Mangelis, Panagiotis, Lei, Hechang, McDonnell, Marshall, Feygenson, Mikhail, Petrovic, Cedomir, Bozin, Emil, and Lappas, Alexandros. Tue .  
"On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View".  United States.  https://doi.org/10.3390/condmat3030020.  https://www.osti.gov/servlets/purl/1459171.

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@article{osti_1459171,

  title        = {On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View},

  author       = {Mangelis, Panagiotis and Lei, Hechang and McDonnell, Marshall and Feygenson, Mikhail and Petrovic, Cedomir and Bozin, Emil and Lappas, Alexandros},

  abstractNote = {Comparative exploration of the nanometer-scale atomic structure of KxFe2-yCh2 (Ch = S, Se) was performed using neutron total scattering-based atomic pair distribution function (PDF) analysis of 5 K powder diffraction data in relation to physical properties. Whereas KxFe2-ySe2 is a superconductor with a transition temperature of about 32 K, the isostructural sulphide analogue is not, which instead displays a spin glass semiconducting behavior at low temperatures. The PDF analysis explores phase separated and disordered structural models as candidate descriptors of the low temperature data. For both materials, the nanoscale structure is well described by the iron (Fe)-vacancy-disordered K2Fe5-yCh5 (I4/m) model containing excess Fe. An equally good description of the data is achieved by using a phase separated model comprised of I4/m vacancy-ordered and I4/mmm components. The I4/mmm component appears as a minority phase in the structure of both KxFe2-ySe2 and KxFe2-yS2, and with similar contribution, implying that the phase ratio is not a decisive factor influencing the lack of superconductivity in the latter. Comparison of structural parameters of the Fe-vacancy-disordered model indicates that the replacement of selenium (Se) by sulphur (S) results in an appreciable reduction in the Fe-Ch interatomic distances and anion heights, while simultaneously increasing the irregularity of FeCh4 tetrahedra, suggesting the more significant influence of these factors. Finally, structural features are also compared to the non-intercalated FeSe and FeS parent phases, providing further information for the discussion about the influence of the lattice degrees of freedom on the observed properties in layered iron chalcogenides.},

  doi          = {10.3390/condmat3030020},

  journal      = {Condensed Matter},

  number       = 3,

  volume       = 3,

  place        = {United States},

  year         = {Tue Jul 03 00:00:00 EDT 2018},

  month        = {Tue Jul 03 00:00:00 EDT 2018}

}

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Title: On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View

Abstract

Citation Formats

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Phase relations in K x Fe 2 − y Se 2 and the structure of superconducting K x Fe 2 Se 2 via high-resolution synchrotron diffraction journal, November 2012

Pressure evolution of the low-temperature crystal structure and bonding of the superconductor FeSe ( T c = 37 K ) journal, August 2009

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Title: On the Nanoscale Structure of K_xFe_2-yCh₂ (Ch = S, Se): A Neutron Pair Distribution Function View

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journal, August 2000

Interface-induced superconductivity and strain-dependent spin density waves in FeSe/SrTiO3 thin films
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