“…As it is well known, this model has been analyzed, besides the original mean-field theory [31,32], by a variety of approximations and numerical approaches. These include the real space renormalization group, MC simulations, and MC renormalization-group calculations [44], ǫ-expansion renormalization groups [45], high-and low-temperature series calculations [46], a phenomenological FSS analysis using a strip geometry [47,48], and, finally, a recent two-parameter WL sampling in rather small lattices of linear sizes L ≤ 16 [49]. As mentioned already in the introduction the phase diagram of the model consists of a segment of continuous Ising-like transitions at high temperatures and low values of the crystal field which ends at a tricritical point, where it is joined with a second segment of first-order transitions between (∆ t , T t ) and (∆ = 2, T = 0).…”