Evidence for the d'Almeida-Thouless transition line in a dilute metallic spin glass from time response measurements near Tg

An analysis of measurements of the field (H) and temperature (T) dependence of the time decay of the thermoremanent magnetization of the dilute metallic spin glass, Ag:Mn2.6Sb0.46 (at . %), are presented for temperatures just below the glass temperature (Tg=9.30 K). The thermoremanent magnetization, σTRM(t), is found to decay with time t according to a stretched exponential form: σTRM(t) =σ0 exp[−(t/τp)1−n]. Both the T and H dependence of 1/τp and n can be related using a recent model calculation of the nonequilibrium dynamics of the Parisi quantity x for the infinite range Ising model. Within the context of this model, log10(1/τp) is expected to diverge at Tg. It is shown that the experimental data for 1/τp and n are consistent with this theoretical prediction. Moreover, the H and T dependence of n yields an expression for the AT instability line that is in agreement with both theory and previously reported experimental studies.