The $⟨001⟩$ axially symmetric ${\mathrm{Fe}}^{+}\left(\mathrm{II}\right)$ center observed in ${\mathrm{SrCl}}_2:{\mathrm{Fe}}^{2+}$ crystals has been studied by the electron nuclear double resonance $\left(\mathrm{ENDOR}\right)$ technique in the microwave $X$ and $Q$ bands. This center is produced only in crystals grown in chlorine atmosphere and x-ray irradiated at low temperature (below $100\mathrm{K}$). The analysis of the $\mathrm{ENDOR}$ spectra unambiguously confirms the structural model earlier suggested by the electron paramagnetic resonance $\left(\mathrm{EPR}\right)$ study, as a ${\mathrm{Fe}}^{+}$ ion strongly displaced off center along an $⟨001⟩$ axis, almost in the center of the square determined by the four nearest ${\mathrm{Cl}}^{-}$ ligands. The unpaired spin densities $f_{3s}$ and $f_{3p}$ in the $3s$ and $3p$ chlorine orbitals have been determined from the resulting $\mathrm{ENDOR}$ parameters.

• Received 3 March 2004

DOI:https://doi.org/10.1103/PhysRevB.70.024105