Magnetic aging above the freezing temperature in La0.82Sr0.18CoO3

We have performed a detailed study of magnetic relaxation in La0.82Sr0.18CoO3 which shows spin-glass-like behavior at low temperature. Contrary to the case in a classical spin-glass where the collective relaxation behavior is observed only below the freezing temperature T-f, the magnetic relaxation in La0.82Sr0.18CoO3 is found to be of the stretched exponential form not only below but also above T-f. Moreover, the aging effect is also observed above T-f. These results are interpreted in terms of the interactions between ferromagnetic clusters.