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; $A_{|}\text{\hspace{0.17em}=\hspace{0.17em}8.693}\mathrm{MHz}$ and $A_{\perp }\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}6.952}\mathrm{MHz}$ 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⁺.