AN INELASTIC NEUTRON-SCATTERING STUDY OF THE KONDO SEMICONDUCTOR CENISN IN HIGH MAGNETIC-FIELD

We have used inelastic neutron scattering to determine the spin dynami cs in the Kondo insulator CeNiSn under magnetic fields up to 10 T appl ied parallel to the easy a axis. The well known excitations peaked at <(h)over bar omega> = 2 meV located at the Brillouin zone centre and a t <(h)over bar omega> = 4 meV located at the Brillouin zone border wer e 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 t he '4 meV' excitation studied at the scattering vector (00.51), a fiel d as large as 10 T begins to fill in the gap whereas there is no appre ciable change in the spin dynamics between 0 and 6 T. The main feature is the broadening of the response. We compare our experimental result s to recent theoretical developments.