Crystalline electric fields in dilute alloys: Y-Er

From magnetization measurements M(T, theta ) H on erbium doped yttrium single crystals the crystalline electric field parameters and the energy levels of the erbium groundstate 4 I 15/2 have been determined. The experimental results can be explained if the influence of the conduction electrons on the crystalline electric field is considered. Using a modified orthogonalized-plane-wave technique the contribution from the conduction electrons due to their 4f character has been calculated and the degree of 5d admixture has been determined from the experimental crystal field parameters A 2 0 (r 2 ).