An inelastic neutron scattering study of the Kondo semiconductor CeNiSn in high magnetic field

We have used inelastic neutron scattering to determine the spin dynamics in the Kondo insulator CeNiSn under magnetic fields up to 10 T applied parallel to the easy a axis. The well known excitations peaked at ℏω = 2 meV located at the Brillouin zone centre and at ℏω = 4 meV located at the Brillouin zone border were studied comparatively. At the scattering vectors (010) and (001) the peak shifts continuously from 2 to 2.5 meV with the field. No Zeeman splitting could be detected at the accuracy of our measurements. For the '4 meV' excitation studied at the scattering vector (00.51), a field as large as 10 T begins to fill in the gap whereas there is no appreciable change in the spin dynamics between 0 and 6 T. The main feature is the broadening of the response. We compare our experimental results to recent theoretical developments.