Magnetic-Resonance Study of Iron in Silver Chloride

The cubic electron-spin-resonance spectrum of Fe³⁺ in silver chloride has been studied at 1.3^∘{}K by the electron-nuclear-double-resonance (ENDOR) technique. ENDOR lines from 6 to 24 Mc/sec were observed on each of the five electron-spin-resonance transitions and have been identified as lines due to four chlorine nuclei which are nearest neighbors to the iron ion. The angular dependence of the crystal-field splitting of the electron resonance, as the orientation of the applied field is varied, proves that the iron is in a site of cubic symmetry. The angular variation of the ENDOR spectrum, as the field is rotated in a (100) plane, shows that the iron cannot be in a site of octahedral symmetry and that it therefore must be in a site of tetrahedral symmetry. ENDOR lines of both chlorine isotopes were identified. Cl³⁵ ENDOR lines, chartetrahedral by Mₛ=+3/2 and Mₛ=-3/2, were studied with the applied field parallel to the [100] direction, and the best chlorine hyperfine and quadrupole coupling constants were determined for both isotopes. It is found that these constants can be used to predict the locations of all observed Cl³⁵ and Cl³⁷ ENDOR lines, but some discrepancies between the predicted spectrum and the observed lines remain which cannot be accounted for by effects of the cubic-field splitting term in the spin Hamiltonian.