Full Aging in Spin Glasses

The discovery of dynamic memory effects in the magnetization decays of spin glasses in 1983 marked a turning point in the study of the highly disordered spin glass state. Detailed studies of the memory effects have led to much progress in understanding the qualitative features of the phase space. Even so, the exact nature of the magnetization decay functions has remained elusive, causing confusion. In this Letter, we report strong evidence that the thermoremanent magnetization decays scale with the waiting time t_w. By employing a series of cooling protocols, we demonstrate that the rate at which the sample is cooled to the measuring temperature plays a major role in the determination of scaling. As the effective cooling time t^eff_c decreases, t/t_w scaling improves and for t^eff_c<20 s we find almost perfect t/t_w scaling, i.e., full aging.