Phase diagrams of the spin-1 Blume-Emery-Griffiths model in a random transverse field

The effect of the random quantum transverse field Omega on the tricritical behavior of the spin-1 Blume-Emery-Griffiths (BEG) model is studied using an effective field theory. It is found that the tricritical behavior depends on both the biquadratic interaction K, single-ion anisotropy Delta and the concentration p of the disorder of Omega. Indeed, there exists a special value p(1) of the probability p below which the tricritical behavior disappears. In addition, at sufficiently low temperatures, the system exhibits long-range order accompanied by the tricritical behavior below a special value p(2) of the probability p.