Crystal fields at light rare-earth ions in Y and Lu

Crystal-field parameters have been deduced for the light rare-earth solutes Ce, Pr, and Nd in Y or Lu hosts from measurements of the paramagnetic susceptibilities. In the analysis all multiplets in the lowest LS term were included. For a given host, crystal-field parameters divided by Stevens factors Blm / αl, are of approximately the same magnitude for all the solutes Pr, Nd, Tb, Dy, Ho, Er, and Tm and do not scale with 〈rl〉.

The values deduced for Ce do not fit in with this simple picture. The higher-order parameters B40, B60, and B66 are, within the errors in their determination, identical in Y and Lu hosts, indicating that these values for a specific rare-earth solute in Y and Lu may give a reliable estimate for the corresponding sites in rare-earth metal.

This is confirmed for Pr, for which these values and the value of B20 deduced from paramagnetic-susceptibility measurements on the pure metal, correctly explain the transition observed by neutron spectroscopy and the level crossing observed in a high-field experiment. A weighted average of B20 for cubic and hexagonal sites in Nd and Sm was obtained from the paramagnetic susceptibilities of these metals at high temperatures.