Monte carlo studies of the dynamics of reentrant ising spin glasses

The temperature, frequency, and field dependence of the ac susceptibility of a three-dimensional Ising spin glass with a Gaussian nearest-neighbor bond distribution has been studied. The results are in good qualitative agreement with experimental results. In the symmetric-bond-distribution (J(0)=0) case, the observed field dependence can be understood in terms of the difference in the field dependence of the high-temperature equilibrium regime and the low-temperature nonequilibrium regime, with a crossover at a frequency-dependent freezing temperature T-f(omega). In the ferromagnetic case J(0)/J=0.8, chi is strongly nonlinear near the ferromagnetic transition, but at lower temperatures, a low-field linear-response regime is found. A second maximum in chi '' can be seen in this low-temperature region and it is even more pronounced for even lower frequencies. In the antiferromagnetic cases J(0)/J=-0.7 and -0.8, a peak in chi' is found at a temperature substantially higher than the corresponding temperature for J(0)=(0) and there is a small maximum in chi '' at a slightly lower temperature. At a temperature significantly fewer, a second, more pronounced, maximum in chi '' can be seen.