  We report a detailed investigation of magnetic relaxation and memory effects
in La$_{0.9}$Sr$_{0.1}$CoO$_3$ single crystal from dc magnetization
measurements. The analysis of magnetic relaxation at different temperatures and
magnetic fields below the freezing temperature ($T_{f}$) manifests the
characteristics of 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 co-operative spin-spin interaction but
not due to the independent relaxation of metastable phase clusters. The
asymmetric response with respect to negative and positive temperature change
favors the hierarchical model of memory effects rather than the droplet model
discussed in other works for different insulating and metallic Heisenberg spin
glasses.
