The effect of Co doping on antiferromagnetic correlations in the Kondo semi-metal CeNiSn

Single-crystal neutron scattering experiments have been performed to study magnetic excitations in CeNi0.9Co0.1Sn, in which the pseudo-gap of CeNiSn is suppressed by the doping. In CeNiSn there are two inelastic excitation peaks at <(h)over bar omega> = 2 and 4 meV, which correspond to dynamic antiferromagnetic correlations. In CeNi0.9Co0.1Sn the 2 meV peak is smeared out, whereas the 4 meV peak becomes very weak and broad, but preserves the same quasi-one-dimensional character as that for CeNiSn. These results suggest the strong relation between the antiferromagnetic correlations and the pseudo-gap formation.