Slow dynamics in the 'Griffiths phase' of the 3D +/-J Ising spin glass

Slow dynamics in the 'Griffiths phase' of the 3D +/-J Ising spin glass is studied by means of Monte Carlo simulation, in which the spectra of (logarithms of) relaxation times, P(x) with x=ln tau, are analyzed in detail. At each temperature P(x) exhibits a characteristic crossover behavior at around a certain value x(c) which in turn tends to diverge toward the spin-glass critical temperature T-c. The contributions to the branch x less than or equal to x(c) are interpreted due to the ordinary critical slowing down process associated with T-c (critical dynamics). The behavior of P(x) at x greater than or equal to x(c), on the other hand, is consistent with the picture of relaxation processes of large, rare clusters which are related to the Griffiths singularity at the Curie temperature of the corresponding pure ferromagnet (cluster dynamics).