Observation of a time-dependent spatial correlation length in a metallic spin glass

The aging process in a Cu (10 at.% Mn) spin glass has been investigated by means of zero-field-cooled magnetization measurements. A small persistent temperature shift immediately prior to the field application is found to have a very specific influence on the measured relaxation of the magnetization. It is inferred that the aging process may be interpreted in terms of a spatial correlation length that increases with the age of the system. The correlation length also governs the time scales where a crossover from equilibrium dynamics to nonequilibrium dynamics occurs.