Dielectric loss and EPR studies of CaF₂:Gd³⁺

Dielectric loss measurements on CaF 2 :Gd 3+ show four relaxation absorptions. By correlation with EPR the assignment of a relaxation with activation energy 0.396 eV to a tetragonal site is confirmed. Evidence against assignment of a relaxation with activation energy 0.68 eV to a trigonal site is obtained. Relaxations with activation energy 0.15 eV and 0.076 eV are tentatively assigned to aggregates. Relaxation of the tetragonal Gd 3+ -H 1 - and Gd 3+ -D 1 - sites is shown by EPR to have an activation energy close to the Gd 3+ -F 1 - site but is not observed in the dielectric spectrum.