“…An alternative is to use a full crystal field model for the whole 4f configuration of the rare earth ion, including interactions that generate hyperfine structure. These types of models have been successfully applied for several different hosts doped with Kramers and non-Kramers rare earth ions, including Pr 3+ [5,[7][8][9][10], Er 3+ [11][12][13][14], Ho 3+ [7,[15][16][17][18][19][20][21], Tb 3+ [22,23], and Tm 3+ [4,10]. However, a complete crystal field calculation of Eu 3+ Zeemanhyperfine structure has not been demonstrated.…”