ESR and ENDOR Spectra of Gd3+ in CdF2

ENDOR and ESR have been used to measure the spin-Hamiltonian parameters for Gd3+ ions in single crystals of CdF2. Measurements were made in insulating and semiconducting crystals. In both cases the predominant ESR spectrum arose from substitutional Gd3+ in cubic sites. Hyperfine splittings for the 155Gd and 157Gd were 12.8414 and 16.856 MHz, respectively. Parallel and perpendicular components of the hyperfine tensors of surrounding 19F nuclei were; A| = 8.693 MHz and A⊥ = − 6.952 MHz for the nearest-neighbor fluorines. More distant fluorine hyperfine splittings out to the fourth-nearest-neighbor shell have been measured and are found to fit closely to a point-dipole model. No differences in ESR and ENDOR Hamiltonian parameters, outside experimental errors have been found for Gd3+ between insulating and semiconducting CdF2 at low temperatures. Specifically, no charge-compensating F− ion was found within 7 Å of the Gd3+. The ENDOR measurements give values for the magnetic moments of 155Gd and 157Gd of − 0.2549 and − 0.3314 nuclear magnetons. A hyperfine anomaly of 1% was found for the Gd3+.