Anisotropic Neutron Spin Resonance in Superconducting BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$

O. J. Lipscombe, Leland W. Harriger, P. G. Freeman +8

We use polarized inelastic neutron scattering to show that the neutron spin resonance below $T_c$ in superconducting BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$ ($T_c=20$ K) is purely magnetic in…