Unified phase diagram of F-doped LaFeAsO by means of NMR and NQR parameters

We present As75 nuclear magnetic and quadrupole resonance results (NMR, NQR) on a new set of LaFeAsO1−xFx polycrystalline samples. Improved synthesis conditions led to more homogenized samples with better control of the fluorine content. The structural≡nematic, magnetic, and superconducting transiti...

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Bibliographic Details
Published in:Physical review. B 2020-02, Vol.101 (5), p.1, Article 054519
Main Authors: Grafe, Hans-Joachim, Lepucki, Piotr, Witschel, Markus, Dioguardi, Adam P., Kappenberger, Rhea, Aswartham, Saicharan, Wurmehl, Sabine, Büchner, Bernd
Format: Article
Language:English
Subjects:
Doping
Fluorine
Magnetic permeability
Magnetism
NMR
Nuclear magnetic resonance
Phase diagrams
Quadrupoles
Spin-lattice relaxation
Superconductivity
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Summary:We present As75 nuclear magnetic and quadrupole resonance results (NMR, NQR) on a new set of LaFeAsO1−xFx polycrystalline samples. Improved synthesis conditions led to more homogenized samples with better control of the fluorine content. The structural≡nematic, magnetic, and superconducting transition temperatures have been determined by NMR spin-lattice relaxation rate and AC susceptibility measurements. The so-determined phase diagram deviates from the published one, especially for low F-doping concentrations. However, if the doping level is determined from the NQR spectra, both phase diagrams can be reconciled. The absence of bulk coexistence of magnetism and superconductivity and a nanoscale separation into low-doping-like and high-doping-like regions have been confirmed. Additional frequency-dependent intensity, spin-spin, and spin-lattice relaxation rate measurements on underdoped samples at the boundary of magnetism and superconductivity indicate that orthorhombicity and magnetism originate from the low-doping-like regions, and superconductivity develops first in the high-doping-like regions.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.101.054519