Existence of a tricritical point at finite field in the three-dimensional random-field Ising model

Abstract

The critical behavior of the random-field Ising model with a bimodal field distribution is studied using standard and histogram Monte Carlo calculations. It is definitely found that the transition is second order for weak fields while it becomes first order for higher fields. The existence of this crossover, discovered here in Monte Carlo simulations, is in contradiction with earlier Monte Carlo works, but in agreement with mean-field predictions. Estimates of the critical exponents of the model at low field are given.