SLOW DYNAMICS IN THE GRIFFITHS PHASE OF THE 2-DIMENSIONAL ISING SPIN-GLASS

Slow dynamics in the +/-J Ising model on a square lattice is studied by means of Monte Carlo simulation, in which the distribution function of (logarithms of) relaxation times, P(x) with x=ln tau, is obtained by analyzing individual spin auto-correlation functions one by one. At each temperature in the 'Griffiths phase', namely in the range above the spin-glass transition temperature T-c(=0) but below the Curie temperature of the corresponding pure ferromagnet T-c(pure), P(x) exhibits a characteristic crossover behavior at around x(c)(=ln tau(c)) which diverges toward T-c. The contributions to the branch x less than or similar 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 similar to x(c), on the other hand, is quite consistent with the picture of relaxation processes of large, rare clusters related to the expected Griffiths singularity at T-c(pure) (cluster dynamics).