Ferromagnetic transition of ±J Ising spin glass model on square lattice

The ferromagnetic transition of +/-J-Ising spin-glass model on square lattice is studied by using Monte Carlo simulation. At ferromagnetic-bond density p = 0.96 where the system shows ferromagnetic transition, the spontaneous magnetization, the ratio [m(4)]/[m(2)](2) and the nonequilibrium relaxation (NER) are studied. The transition is estimated to he at K-c = 0.5100(1). The analysis by NER gives the most reliable estimation with the least CPU time for simulations among the three methods. The value of magnetization exponent beta is estimated to he 0.130(10) which coincides with that of the purely ferromagnetic Ising model (p = 1). The dynamical critical exponent 2 is estimated to be 2.418(23) from the NER analysis which is different from that of the pure model. The size of simulated lattices is up to 2001 x 2000, and the number of totally updated Ising spins is 5.5 x 10(15).