NEUTRON-SCATTERING DETERMINATION OF THE CRYSTAL-FIELD PARAMETERS IN ERCU4AL8 AND ERFE4AL8 INTERMETALLICS

An inelastic neutron scattering experiment has been performed in order to determine the crystal field potential acting at the rare earth sit e in the paramagnetic phase of ErCu4Al8 and ErFe4Al8 intermetallic com pounds. The profile refinement of the spectra measured at different te mperatures, and experimental information on the electric field gradien t available in the literature, allow a reliable estimate of the parame ters for the tetragonal crystal field. Positive values of the lowest o rder term B2(0) suggest an easy plane magnetic anisotropy of the Er su blattice, but the higher order terms could play an important role in d etermining the magnetisation direction.