Antiferromagnetic order in CaK(Fe1-xNix)(4)As-4 and its interplay with superconductivity

Date
2018-06-28
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Goldman, Alan
Kreyssig, Andreas
Wilde, John
Böhmer, Anna
Canfield, Paul
Tian, W.
Meier, William
Li, Bing
Ueland, Benjamin
Xu, Mingyu
Bud’ko, Sergey
Canfield, Paul
McQueeney, Robert
Goldman, Alan
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Ames Laboratory
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Physics and Astronomy
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Ames LaboratoryPhysics and Astronomy
Abstract

The magnetic order in CaK(Fe1−xNix)4 As4 (1144) single crystals (x=0.051 and 0.033) has been studied by neutron diffraction. We observe magnetic Bragg peaks associated with the same propagation vectors as found for the collinear stripe antiferromagnetic (AFM) order in the related BaFe2As2 (122) compound. The AFM state in 1144 preserves tetragonal symmetry and only a commensurate, noncollinear structure with a hedgehog spin-vortex crystal (SVC) arrangement in the Fe plane and simple AFM stacking along the c direction is consistent with our observations. The SVC order is promoted by the reduced symmetry in the FeAs layer in the 1144 structure. The long-range SVC order coexists with superconductivity, however, similar to the doped 122 compounds, the ordered magnetic moment is gradually suppressed with the developing superconducting order parameter. This supports the notion that both collinear and noncollinear magnetism and superconductivity are competing for the same electrons coupled by Fermi surface nesting in iron arsenide superconductors.

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