Abstract
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 (1mT) while its frequency (f) varied in the range 10–104Hz for 5≤T≤300K. The diluted samples presented cusps with maxima distributed around Tf=17.5±0.5K 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=317.6K, T0=4.65K and τ0=10−14s, 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 3.75–3.80eV. The overall χac-data resembles those obtained for cluster spin-glass state.
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