NMR investigation of CdF2 : Ga

Cd-113 nuclear spin-lattice relaxation measurements have been carried out over the temperature range 200-500 K on semiconducting crystals of CdF2 : Ga and co-doped CdF2: Ga,Y. The relaxation rates 1 / T-1 in both crystals are found to be enhanced by two to three orders of magnitude relative to undoped CdF2. We attribute this enhanced relaxation to the effects of thermally excited conduction electrons. The rates in the Y co-doped crystal are systematically about a factor of two higher than are found in CdF2. Analysis of the temperature dependence yields a value DeltaE = 141 +/- 10 meV for both CdF2: Ga and CdF2 : Ga,Y. This result is unexpected in light of the value DeltaE = 185 10 meV found previously for CdF2 : In. and the expectation that the binding energies of the DX-like ground state of the trivalent impurity should lie deeper for CdF2 : Ga. (C) 2001 Elsevier Science B.V. All rights reserved.