Crossover from Commensurate to Incommensurate Antiferromagnetism in Stoichiometric NaFeAs Revealed by Single-Crystal 23Na,75As-NMR Experiments
Abstract
We report the results of 23Na and 75As nuclear magnetic resonance (NMR) experiments on a self-flux grown high-quality single crystal of stoichiometric NaFeAs. The NMR spectra reveal a tetragonal to twinned-orthorhombic structural phase transition at TO = 57 K and an antiferromagnetic (AF) transition at TAF = 45 K. The divergent behavior of nuclear relaxation rate near TAF shows significant anisotropy, indicating that the critical slowing down of stripe-type AF fluctuations are strongly anisotropic in spin space. The NMR spectra at sufficiently low temperatures consist of sharp peaks showing a commensurate stripe AF order with a small moment of ∼0.3 μB. However, the spectra just below TAF exhibit a highly asymmetric broadening pointing to an incommensurate modulation. The commensurate-incommensurate crossover in NaFeAs shows a certain similarity to the behavior of SrFe2As2 under high pressure.
- Publication:
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Journal of the Physical Society of Japan
- Pub Date:
- March 2011
- DOI:
- 10.1143/JPSJ.80.033705
- arXiv:
- arXiv:1011.1108
- Bibcode:
- 2011JPSJ...80c3705K
- Keywords:
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- Condensed Matter - Strongly Correlated Electrons;
- Condensed Matter - Superconductivity
- E-Print:
- 5 pages, 5 figures, revised version to appear in J. Phys. Soc. Jpn