Neutron scattering of iron-based superconductors
Abstract Low-energy spin excitations have been studied on polycrystalline LaFeAsO 1− x F x samples by inelastic neutron scattering. The Q -integrated dynamical spin susceptibility χ ″( ω ) of the superconducting samples is found to be comparable to that of the magnetically ordered parent sample. On the other hand, χ ″( ω ) almost vanishes at x  = 0.158, where the superconducting transition temperature T c is suppressed to 7 K. In addition, χ ″( ω ) in optimally doped LaFeAsO 0.918 F 0.082 with T c  = 29 K exhibits a spin resonance mode. The peak energy, E res , when scaled by k B T c is similar to the value of about 4.7 reported in other high- T c iron-based superconductors. This result suggests that there is intimate relationship between the dynamical spin susceptibility and high- T c superconductivity in iron-based superconductors, and is consistent with a nesting condition between Fermi surfaces at the Γ and M points.