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SUMMARY:Compositional control of magnetism and superconductivity in 111 ir
 on arsenide superconductors - Professor Stephen J. Blundell Department of 
 Physics\, Clarendon Laboratory
DTSTART:20111011T130000Z
DTEND:20111011T143000Z
UID:TALK33995@talks.cam.ac.uk
CONTACT:Mr David Taylor
DESCRIPTION:The response of the superconducting state and crystal structur
 e of LiFeAs and NaFeAs to chemical substitutions on both the Li and the Fe
  sites has been probed using a combination of high-resolution X-ray and ne
 utron diraction measurements\, magnetometry\, and muon-spin rotation spect
 roscopy. The superconductivity is extremely sensitive to\ncomposition: Li-
 deficient materials (Li1-yFe1+yAs with Fe substituting for Li) show a very
  rapid suppression of the superconducting state\, while substitution of Fe
  by small amounts of Co or Ni results in monotonic lowering of the superco
 nducting transition temperature Tc and the superfluid stiffness as the ele
 ctron count increases. A similar effect is found in NaFeAs and it appears 
 that electron count is the dominant factor\, since Ni doping has double th
 e effect of Co doping for the same doping level. The addition of 0.1 elect
 rons per Fe atom is sufficient to traverse the superconducting domain\, an
 d that magnetic order coexists with superconductivity at doping levels les
 s than 0.025 electrons per Fe atom. That the superfluid stiffness in the L
 iFeAs-derived compounds is higher than in all of the iron pnictide materia
 ls underlines the unique position that LiFeAs occupies in this class. We b
 ring together the results of structural and muon measurements\, as well as
  insights from the band structure\, to understand the phase diagrams of th
 ese 111 pnictide superconductors.\n\n[1] D.R. Parker et al.\, Phys. Rev. L
 ett. 104\, 057007 (2010).\n[2] M.J. Pitcher et al.\, J. Am. Chem. Soc. 132
 \, 10467 (2010).\n[3] J.D. Wright et al.\, submitted.\n
LOCATION:TCM Seminar Room (530)
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