Time-differential perturbed-angular-correlation study of hyperfine interactions atCd111in aLi0.5Fe2.5O4single crystal

The time-differential perturbed angular correlation (TDPAC) of γ rays emitted from ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$) on tetrahedral (A) sites in single-crystal ${\mathrm{Li}}_{0.5}$ ${\mathrm{Fe}}_{2.5}$ ${\mathrm{O}}_4$ was measured at room temperature. Expressions for the anisotropy of TDPAC spectra under a hyperfine magnetic field combined with an electric field gradient (EFG) are given explicitly. A least-squares fitting of the data with these expressions reveals that ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}_{}^{2+}{}_{}{}^{}$(A) experiences a supertransferred hyperfine magnetic field, $H_{\mathrm{STHF}}$, of 112 kOe parallel to the net magnetization of the specimen and an axially symmetric EFG of 90×${10}^{13}$ esu. The observed $H_{\mathrm{STHF}}$ is seen to be the sum of the supertransferred ones from the ${\mathrm{Fe}}^{3+}$(B) ions on the nearest-neighbor B sites. The magnitude of the transferred field from each individual ${\mathrm{Fe}}^{3+}$(B) ion is estimated to be 13.3 or 11.0 kOe, depending on whether the intervening ${\mathrm{O}}^{2\mathrm{-}}$ ion has ${\mathrm{Li}}^{1+}$(B) as its neighbor or not. The remarkably large EFG at ${\mathrm{Cd}}^{2+}$(A) observed in this ferrite is interpreted qualitatively as being caused by the presence of the weakly electronegative next-nearest ${\mathrm{Li}}^{1+}$(B) ions.