Abstract
The g values of rare earth ions obtained from either paramagnetic resonance or Zeeman measurements are often used to interpret the location and/ or environment surrounding rare earth ions. In the case of centres with cubic symmetry the g value can be used to distinguish between substitutional and interstitial sites. For centres with less than cubic symmetry the average g value, taken as 1/3 trace of the g tensor, is often used as an indication of the lattice location and/or a measure of the strength of the local crystal field. This approach is widely used but is based on the assumption that the non-cubic terms in the total crystal field potential are small compared with the cubic crystal field. In this paper we have explored this assumption by calculating the principal g values in axial crystal fields for the Er ion. We examine the limits over which the average g value approach is valid. Comparison is made with published results. © 2005 Materials Research Society.