Evidence for Power-Law Spin-Correlation Decay from Muon Spin Relaxation inAgMnSpin-Glass

Muon spin relaxation measurements have been carried out below the "glass" temperature $T_g$ in $\mathrm{Ag}\mathrm{Mn}$ spin-glasses. The muon spin-lattice relaxation rate varies with field $H$ as $H^{-0.46\mathrm{}\pm 0.05}$ for $0.30<~\frac{T}{T_g}<~0.66$. This suggests that impurity-spin correlations decay with time as $t^{-\nu }$, $\nu \simeq 0.54\pm 0.05$, in contrast to the more usual exponential decay. The present data therefore agree quantitatively with the prediction $\nu \simeq \frac{1}{2}$ of mean-field dynamic theories.