Low energy excitations in CeNiSn

We have studied the magnetic excitation spectrum of CeNiSn at low energies both on a polycrystalline sample using time-of-flight technique and on a si ngle crystal with a triple axis spectrometer. The energy gap in the excitat ion spectrum is clearly observed in the polycrystalline sample reconciling the earlier discrepancies between the two kinds of measurements. The experi mental results are consistent with the occurrence of a quasielastic signal within the gap without any significant wave vector dependence and character ized by an energy scale Gamma approximate to 0.2 meV. (C) 1998 Elsevier Sci ence B.V, All rights reserved.