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Title: Detailed magnetic and structural analysis mapping a robust magnetic C4 dome in Sr1-xNaxFe2As2

The recently discovered C4 tetragonal magnetic phase in hole-doped members of the iron-based superconductors provides new insights into the origin of unconventional superconductivity. Previously observed in Ba1-xNaxFe2As2 (with A = K, Na), the C4 magnetic phase exists within the well studied C2 spin-density wave (SDW) dome, arising just before the complete suppression of antiferromagnetic (AFM) order but after the onset of superconductivity. Here in this paper, we present detailed x-ray and neutron diffraction studies of Sr1-xNaxFe2As2 (0.10 ≤ x ≤ 0.60) to determine their structural evolution and the extent of the C4 phase. Spanning Δx ~ 0.14 in composition, the C4 phase is found to extend over a larger range of compositions, and to exhibit a significantly higher transition temperature, Tr ~ 65K, than in either of the other systems in which it has been observed. The onset of this phase is seen near a composition (x~0:30) where the bonding angles of the Fe2As2 layers approach the perfect 109.46° tetrahedral angle. We discuss the possible role of this return to a higher symmetry environment for the magnetic iron site in triggering the magnetic reorientation and the coupled re-entrance to the tetragonal structure. Finally, we present a new phase diagram, completemore » with the C4 phase, and use its observation in a third hole-doped 122 system to suggest the universality of this phase.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [1] ;  [3] ;  [3] ;  [5] ;  [3] ;  [3] ;  [1]
  1. Northern Illinois Univ., DeKalb, IL (United States). Dept. of Physics; Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Chemistry
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
  5. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 93; Journal Issue: 13; Journal ID: ISSN 2469-9950
American Physical Society (APS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1248253