The influence of the crystal field on the anisotropic thermal expansion in TmCu₂

The lattice parameters a, b and c of TmCu₂ have been measured in the temperature range from 4.2 K up to 300 K using X-ray powder diffraction. The influence of the crystal field on the thermal expansion in TmCu₂ in the paramagnetic region has been determined by comparing the thermal expansion of the non-magnetic YCu₂ with that of TmCu₂ (TmCu₂ orders magnetically at T_N=6.3 K). The data thus obtained are compared with a theoretical model given by Gratz et al. in 1993 using a set of crystal field parameters published by Gubbens et al. in 1992. From this analysis we get information about the unknown elastic and magnetoelastic properties of TmCu₂.