2023/10/05 by Roy-Chowdhury, Mouli, Seehra, Mohindar S., Thota, Subhash · 2 citations
#Disordered Systems and Neural Networks (cond-mat.dis-nn) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2310.13706
In spin-glasses (SG), the relaxation time τ (= 1/2πf) vs. Tf data at the peak position Tf in the temperature variation of the ac magnetic susceptibilities at different frequencies f is often fit to the Vogel-Fulcher Law (VFL): τ=τ0exp[Ea/kb(Tf-T0)] and to the Power Law (PL): τ= τ0^*[(Tf-TSG/TSG]-zν. Both these laws have three fitting parameters each, leaving a degree of uncertainty since the magnitudes of the evaluated parameters τ0, Ea/kB, τ0^* and zν depend strongly on the choice of T0 and TSG. Here we report an optimized procedure for the analysis of τ vs. Tf data on several SG systems for which we could extract such data from published sources. In this optimized method, the data of τ vs. Tf are fit by varying T0 in the linear plots of ln τ vs 1/ (Tf - T0) for the VFL and by varying TSG in the linear plot of ln τ vs. ln (Tf - TSG)/ TSG for the PL till optimum fits are obtained. The analysis of the associated magnitudes of τ0, Ea/kB, τ0^* and zν for these optimum values of T0 and TSG shows that magnitudes of τ0^*, τ0 and zν fail to provide a clear distinction between canonical and cluster SG. However, new results emerge showing Ea/(kBT0) < 1 in canonical SG whereas Ea/(kBT0) >1 for cluster SG systems and the optimized T0 < optimized TSG in all cases. Although some interpretation of these new results is presented, a more rigorous theoretical justification of the boundary near Ea/(kBT0) ∼ 1 is desired along with testing of these criteria in other SG systems.