Using high resolution superconducting quantum interference device magnetometry we have made detailed measurements of the waiting time effect of the thermoremanent magnetization (TRM) decays on a single-crystal $\mathrm{Cu}\mathrm{Mn}(6\%)$ spin-glass sample near $T_g$. We have systematically mapped the rapid decrease of the characteristic timescale ${\mathrm{tw}}_{\mathrm{eff}}$, approaching $T_g$ from below, for waiting times ranging from 100 to 100 000 s. Using ${\mathrm{tw}}_{\mathrm{eff}}$ to determine the length scale of the growth of correlations during the waiting time, ${\xi }_{\mathrm{TRM}}$ (observed in both numerical studies and experiment), we observe both growth of ${\xi }_{\mathrm{TRM}}$ in the spin-glass phase and then a rapid reduction very close to $T_g$. We interpret this reduction in ${\xi }_{\mathrm{TRM}}$, for all waiting times, as being governed by the critical correlation length scale ${\xi }_{\mathrm{crit}}=a{(T-T_c)}^{-\nu }$.

• Received 25 March 2020
• Revised 10 August 2020
• Accepted 11 August 2020

DOI:https://doi.org/10.1103/PhysRevB.102.064427