Time-differential perturbed-angular-correlation study of hyperfine interactions atCd111(←111In) in α-Fe2O3

Hyperfine interactions at ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$(${\leftarrow }^{111}$In) atoms on ${\mathrm{Fe}}^{3+}$ sites in α-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ are studied in a wide temperature range from 85 to 987 K by means of time-differential perturbed-angular-correlation measurements. The observed hyperfine interaction is unique at high temperatures above ∼700 K but is distributed at lower temperatures owing to the aftereffects of ${}_{}{}^{111}{}_{}{}^{}\to _{}^{111}{}_{}{}^{}$Cd electron-capture decay. The spectra modified by the aftereffects are analyzed successfully with a static distribution of the electric field gradient (EFG) in the temperature region above the Morin temperature (${\mathit{T}}_{\mathit{M}}$=260 K). On the other hand, the spectra below ${\mathit{T}}_{\mathit{M}}$ are analyzed with a large distribution of hyperfine frequencies, which diminishes rapidly in a short period of about 40 ns.