Publication Type
Journal
Journal Name
Physical Review Letters
Publication Date
Page Number
087002
Volume
103
Issue
8
Abstract
We report neutron scattering measurements on single crystals of BaFe1.92Co0.08As2. The magnetic
Bragg peak intensity is reduced by 6 % upon cooling through TC. The spin dynamics exhibit a
gap of 8 meV with anisotropic three-dimensional (3d) interactions. Below TC additional intensity
appears at an energy of 4.5(0.5) meV similar to previous observations of a spin resonance in other
Fe-based superconductors. No further gapping of the spin excitations is observed below TC for
energies down to 2 meV. These observations suggest the redistribution of spectral weight from the
magnetic Bragg position to a spin resonance demonstrating the direct competition between static
magnetic order and superconductivity.
