We report a 23Na and 75As nuclear magnetic resonance (NMR) investigation of NaxFeAs series (x=1, 0.9, 0.8) exhibiting a spin-density-wave (SDW) order below TSDW=45, 50, and 43 K for x=1, 0.9, 0.8, respectively, and a bulk superconductivity below Tc≈12 K for x=0.9. Below T SDW, a spin-lattice relaxation reveals the presence of gapless particle-hole excitations in the whole x range, meaning that a portion of the Fermi surface remains gapless. The superconducting fraction as deduced from the bulk susceptibility scales with this portion, while the SDW order parameter as deduced from the NMR linewidth scales inversely with it. The NMR line shape can only be reproduced assuming an incommensurate (IC) SDW. These findings qualitatively correspond to the mean-field models of competing interband magnetism and intraband superconductivity, which lead to an IC SDW order coexisting with superconductivity in part of the phase diagram.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 2011 Aug 11
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics