Destruction of first-order phase transition in a random-field Ising model

The phase transitions that occur in an infinite-range-interaction Ising ferromagnet in the presence of a double Gaussian random magnetic field are analyzed. Such random fields are defined as a superposition of two Gaussian distributions, presenting the same width σ. It is argued that this distribution is more appropriate for a theoretical description of real systems than other simpler cases, i.e. the bimodal (σ = 0) and single Gaussian distributions. It is shown that a low-temperature first-order phase transition may be destroyed for increasing values of σ, similarly to what happens in the compound Fe x Mg 1− x Cl 2 , whose finite-temperature first-order phase transition is presumably destroyed by an increase in the field randomness.