Ac magnetic susceptibility measurements in nanoparticulate powders of iron-doped ZnO

Low temperature (T) ac magnetic susceptibility (χac) measurements were performed in powder samples of the Zn1−xFexO (x=0–0.078) prepared by a combustion reaction method. The amplitude of the ac magnetic field was kept constant (1 mT) while its frequency (f) varied in the range 10–104 Hz for 5≤T≤300 K. The diluted samples presented cusps with maxima distributed around Tf=17.5±0.5 K while no such feature was observed for the pure sample (x=0). The cusp was found to become more pronounced with the increasing Fe content. Also it decreased and shifted to higher values of T by increasing f. The shift in Tf was found to follow a Vogel–Fulcher law with Ea/kB=317.6 K, T0=4.65 K and τ0=10−14 s, for the activation energy, critical temperature and characteristic time-constant, respectively. The energy gap of the sample was measured and they were found to vary in the range 3.75–3.80 eV. The overall χac-data resembles those obtained for cluster spin-glass state.

▸ Low temperature (T) ac magnetic susceptibility (χac) measurements. ▸ Zn1−xFexO prepared by a combustion reaction method. ▸ Spin-glass phase. ▸ High energy gap semiconductors.