Tricritical point in random-field Ising model

The numerical investigation of the random-field Ising model by Houghton, Khurana, and Seco1 has revealed a number of interesting features concerning the three-dimensional Ising model in a random external field Bt. Earlier, Aharony2 had already found that even in a mean-field approximation the bimodal [Bi= ?B] and Gaussian [P{Bi) ~ exp(-B2t/2B2)] distributions led to different phase diagrams.