Phase diagram and tricritical behavior of an metamagnet in uniform and random fields

Phase diagram of the classical Heisenberg model in a trimodal random field distribution

“…A problem associated with the ferromagnetic model in a random field is the survival of the tricritical point [10][11][12][13][14]. Depending on the choice of the random-field distribution, for example when it is given by a symmetric double-delta functions [15], the mean-field approximation gives rise to a tricritical point.…”