Electron-trapped ${\mathrm{Fe}}^{+}$-type centers, produced by x-ray irradiation at $80\mathrm{K}$ and further annealing at higher temperatures in iron-doped ${\mathrm{SrCl}}_2$ single crystals grown in chlorine gas, have been investigated by electron paramagnetic resonance. The ${\mathrm{Fe}}^{+}\left(\mathrm{III}\right)$ and ${\mathrm{Fe}}^{+}\left(\mathrm{IIIa}\right)$ centers, produced by annealing at temperatures higher than $200\mathrm{K}$, exhibit monoclinic local symmetry with the two $\stackrel{⃡}{g}$- tensor principal axes situated in the (110) plane slightly tilted away from the [001] and [1–10] directions, respectively. The ${\mathrm{Fe}}^{+}\left(\mathrm{IV}\right)$ center, observed after several cycles of irradiation and annealing to $700\mathrm{K}$, exhibits tetragonal local symmetry around $⟨100⟩$ and a well-resolved four-component structure, attributed to the superhyperfine interaction with a neighboring monovalent impurity ion. The presence and properties of the low symmetry radiation-induced ${\mathrm{Fe}}^{+}$ paramagnetic centers are attributed to trapping and the thermally activated movement of chlorine interstitials. Both precursor ${\mathrm{Fe}}^{2+}$ and resulting ${\mathrm{Fe}}^{+}$ centers are perturbed by these interstitials, which are introduced in ${\mathrm{SrCl}}_2:\mathrm{Fe}$ crystals during growth under a chlorine atmosphere.

• Received 12 January 2006

DOI:https://doi.org/10.1103/PhysRevB.73.174103