Polarized neutron scattering studies of magnetic excitations in iron-selenide superconductor LiFeODFeSe (41 K).

We report polarized neutron scattering measurements of the low energy spin fluctuations of the iron-selenide superconductor LiFeODFeSe below and above its superconducting transition temperature= 41 K. Our experiments confirmed that the resonance mode near 21 meV is magnetic. Moreover, the spin excitations are essentially isotropic in spin space at 5 ⩽⩽ 29 meV in the superconducting and normal states. Our results suggest that the resonance mode in iron-based superconductors becomes isotropic when the influence of spin-orbit coupling and magnetic/nematic order is minimized, similar to those observed in cuprate superconductors.