Slowing down of spin glass correlation length growth: simulations meet experiments*

The aging rate, d ln t_w /d ln ξ = (T_c/T) z_c(T,ξ), of the spin glass correlation length ξ has been measured in a single crystal of CuMn (6 at.%) as a function of the waiting time, t_w, where T_c is the critical temperature. Dynamic slowing down is observed with ξ reaching a value of
ξ = 152 nm. The measurements were performed at T/T_c = 0.89 and for times 2 × 10³ ≤ t_w ≤ 8 × 10⁴ s. The value of the crossover variable, x(t_w,T) = l_J(T)/ξ(t_w,T), where l_J(T) is the Josephson length, is sufficiently small (0.091 ≤ x ≤ 0.12) that the experimental results are free from critical effects. The measured aging rate (z_c = 12.37 ± 1.07) was compared with simulation results from the Janus Collaboration. An extrapolation of the Janus results yields z_c(115 nm) = 11.94 ± 0.08 and z_c(152 nm) = 12.76 ± 0.08. This relationship between simulations and experiments allows exploration of phenomena, especially in complex systems, with the particular insights of each partner fueling the interpretation and development of the other. [Phys. Rev. B 100, 094202 (2019)]