Coexistence of ferromagnetic and glassy behavior in the La0.5Sr0.5CoO3 perovskite compound

Dc magnetization, ac susceptibility, and zero-field-cooled relaxation measu rements are carried out for a cluster glass compound of La0.5Sr0.5CoO3. The temperature dependence of the magnetic properties could be distinguished i nto two regimes: a high-temperature regime with the time-independent parame ters originating probably from the intracluster ferromagnetism, and a lower -temperature regime where the freezing of clusters takes place with a consi derabe frequency dependence of a shoulder in chi'(T) and a hump in chi "(T) The cusp in M-ZFC(T) at T-a, as well as the high-temperature maximum in ch i'(T) are discussed in terms of an existence of the local anisotropy inside the clusters. The high-temperature maximum in chi "(T) is interpreted in c onnection to the reversibility temperature, T-r. Empirically, we found T-r( proportional to) - H while T-a(proportional to) - H-0.58. We report also th e long-time relaxation and the ageing phenomenon in this compound. The agei ng effect is much more pronounced in the ferromagnetic state than in the du ster glass state and the system does not reach equilibrium for time scales up to 10(4) s. The relaxation and ageing effects are attributed to the clus ter growth slowed down by the presence of the frustration. [S0163-1829(99)0 0105-8].