Neutron scattering of iron-based superconductors

Low-energy spin excitations have been studied on polycrystalline LaFeAsO1−xFx 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 Tc is suppressed to 7 K. In addition, χ″(ω) in optimally doped LaFeAsO0.918F0.082 with Tc = 29 K exhibits a spin resonance mode. The peak energy, Eres, when scaled by kBTc is similar to the value of about 4.7 reported in other high-Tc iron-based superconductors. This result suggests that there is intimate relationship between the dynamical spin susceptibility and high-Tc superconductivity in iron-based superconductors, and is consistent with a nesting condition between Fermi surfaces at the Γ and M points.

► Spin excitations of LaFeAsO1-xFx studied by inelastic neutron scattering. ► Fluorine content dependence of the dynamical spin susceptibility. ► Fe 3d orbital contribution on the dynamical spin susceptibility. ► The electron scattering between Gamma and M Fermi surfaces.