Orientation kinetics of Gd³⁺-F^-interstitial pairs in CaF₂

Abstract

The e.s.r. spectrum from substitutional Gd3+ ions with adjacent trapped F- interstitials broadens significantly above about 100 degrees C. The temperature-dependent part of the relaxation time associated with this broadening is compatible with the relaxation time derived by dielectric relaxation measurements on identically treated crystals. These results are interpreted in terms of the orientational diffusion of the trapped F- interstitial ion around the immobile Gd3+ ion in a cation site. The relaxation time is given by tau = tau 0 exp (Q/kT), with tau 0=8.2*10-14 s and Q=0.38 eV.