CRYSTAL-FIELD INVESTIGATION OF DYNI2SI2

Inelastic neutron scattering experiments on the tetragonal compound Dy Ni2Si2 are reported. From these results combined with previous measure ments of heat capacity and magnetization, several crystal field level schemes are proposed. By using the periodic field model, they allow us to explain qualitatively the magnetic behaviour within the antiferrom agnetic phase, in particular the existence of two field-induced long-p eriod magnetic arrangements at 1.5 K along the [001] easy axis.