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Accession Number
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DE2012-1048278
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Title
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Magnetic Ordering in Tetragonal FeS: Evidence for Strong Itinerant Spin Fluctuations.
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Publication Date
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Nov 2010
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Media Count
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25p
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Personal Author
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G. Sposito K. Refson K. D. Kwon R. Qiao S. Bone W. L. Yang Z. Liu
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Abstract
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Mackinawite is a naturally-occurring layer type FeS mineral important in biogeochemical cycles and, more recently, in the development of microbial fuel cells. Conflicting results have been published as to the magnetic properties of this mineral, with Mossbauer spectroscopy indicating no magnetic ordering down to 4.2 K but density functional theory predicting an antiferromagnetic ground state, similar to the Fe-based high-temperature superconductors with which it is isostructural and for which it is known that magnetism is suppressed by strong itinerant spin fluctuations. We investigated this latter possibility for mackinawite using photoemission spectroscopy (PES), near-edge X-ray absorption fine structure spectroscopy (XAS), and density functional theory (DFT) computations. Our Fe 3s core-level PES spectrum of mackinawite showed a clear exchange-energy splitting (2.9 eV) consistent with a 1 EB magnetic moment on the Fe ions, while the Fe L-edge XAS spectrum indicated rather delocalized Fe 3d electrons in mackinawite similar to those in Fe metal. DFT computations demonstrated that the ground state of mackinawite is esingle-stripe antiferromagnetic, with an Fe magnetic moment (2.7 EB) that is significantly larger than the experimental estimate and has a strong dependence on the S height and lattice parameters. All of these trends signal the existence of strong itinerant spin fluctuations. If spin fluctuations prove to be mediators of electron pairing, we conjecture that mackinawite may be one of the simplest Fe-based superconductors.
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Keywords
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Absorption
Electrons
Fine structure
Fluctuations
Fuel cells
Functionals
Ground states
Lattice parameters
Magnetic moments
Magnetic ordering
Magnetic properties
Moessbauer effect
Photoemission
Spectroscopy
Spin
Superconductors
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Source Agency
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Technical Information Center Oak Ridge Tennessee
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NTIS Subject Category
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46D - Solid State Physics
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Corporate Author
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Lawrence Berkeley National Lab., CA. Earth Sciences Division.
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Document Type
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Technical report
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Title Note
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N/A
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NTIS Issue Number
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1303
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Contract Number
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DE-AC02-05CH11231
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