First-order transition features of the 3D bimodal random-field Ising model

Two numerical strategies based on the Wang–Landau and Lee entropic sampling schemes are implemented to investigate the first-order transition features of the 3D bimodal (± h) random-field Ising model at the strong disorder regime. We consider simple cubic lattices with linear sizes in the range L = 4–32 and simulate the system for two values of the disorder strength: h = 2 and 2.25. The nature of the transition is elucidated by applying the Lee–Kosterlitz free-energy barrier method. Our results indicate that, despite the strong first-order-like characteristics, the transition remains continuous, in disagreement with the early mean-field theory prediction of a tricritical point at high values of the random field.