The effect of nonmagnetic disorder on phase transitions of the first-order

Using the Monte Carlo method, weakly dilute magnetic systems described by two-dimensional 5-state Potts model, which in the pure state undergoes a phase transition first-order. Numerical studies have revealed that an insignificant quenched disorder, realized in the form of nonmagnetic impurities, can change the order of phase transition in magnetic systems described by the two-dimensional 5-state Potts model on a square lattice, for which a phase transition of the first-order is observed in a homogeneous state. It is shown that such a phase change the transition is due to the fact that nonmagnetic disorder prevents the coexistence of local phases characteristic of a phase transition of the first-order at $T=T_l$.