Sep 15 – 16, 2011
Paul Scherrer Institut, Villigen, Switzerland
Europe/Zurich timezone

Magnetism and superconductivity in the iron-based superconductors LiFeAs and NaFeAs

Sep 15, 2011, 5:30 PM
30m
WHGA/001 (Paul Scherrer Institut, Villigen, Switzerland)

WHGA/001

Paul Scherrer Institut, Villigen, Switzerland

Talk Plenary session Plenary session

Speaker

Dr Tom Lancaster (University of Oxford, UK)

Description

The response of the superconductivity and structure of LiFeAs and NaFeAs to chemical substitutions has been probed using high-resolution X-ray diffraction measurements, magnetometry, and muon-spin rotation. The superconductivity is very sensitive to composition, with substitution of Fe by small amounts of Co or Ni in LiFeAs resulting in monotonic lowering of the superconducting Tc and the superfluid stiffness as the electron count increases. A similar effect is found in NaFeAs and it appears that electron count is the dominant factor. I will discuss the interplay and coexistence of superconducting, magnetic and structural order parameters in the latter system, where Co doping weakens the magnetism through both a suppression of T_N and a reduction in the ordered moment in the magnetically ordered phase. Further doping results in a magnetically disordered phase in which moment size continues to decrease and falls to zero at the same point as the structural distortion is removed. Our results suggest that magnetism drives the structural transition in NaFe1-xCoxAs and that its disappearance coincides with a strengthening of the superconducting order.

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Primary author

Dr Tom Lancaster (University of Oxford, UK)

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