Memory effects and magnetic relaxation in single-crystalline La0.9Sr0.1CoO3

We report a detailed investigation of magnetic relaxation and memory effects in La0.9Sr0.1CoO3 single crystal from dc magnetization measurements. The analysis of magnetic relaxation at different temperatures and magnetic fields below the freezing temperature T-f reveals the characteristics of the spin-glass phase. Below T-f, striking memory effects have been clearly observed in different experimental protocols. The memory effect in the zero-field-cooled magnetization further establishes that the glassy magnetic state arises from the cooperative spin-spin interaction but not due to the independent relaxation of metastable phase clusters. The asymmetric response with respect to negative and positive temperature changes favors the hierarchical model of memory effects rather than the droplet model discussed in other works for different insulating and metallic Heisenberg spin glasses.