Simulation Of Non-Equilibrium Phase Transition In A Random Magnetic System

The time-dependent phase transition of a random magnetic system is investigated using a dynamic Monte Carlo simulation. The present random system is a simple dilution of magnetic atoms with Ising spins in a square lattice. The time-dependent order parameters are calculated as a function of temperature for several concentrations of magnetic atoms. The results indicate that as the averaging time becomes shorter, the phase transition becomes more gradual. This tendency is most pronounced around the percolation concentration. These results are compared to results of a recent NMR spin echo experiment on MnxCd1-x (HCOO)(2)center dot 2(NH2)(2)CO reported by Kubo et al. (2007). Although the present simulation includes essentially no adjustable parameter, the results are in satisfactory agreement.