Blume-Emery-Griffiths model for mixed spin

We use the mean-field approximation based on the Bogoliubov inequality to study the ferrimagnetic mixed spin-1 and spin-5/2 Blume-Emery-Griffiths (BEG) model on a hypercube lattice. The effects of the equal crystal field D = D.sub.A = D.sub.B and the ratio of biquadratic and bilinear exchange interactions R = K/|J| are examined by extracting the phase diagrams on the (R = K/|J|; T = 1/z|J|) and (D/z|J|; T = 1/z|J|) planes, respectively. Additionally, we have drawn the phase diagrams in the (D.sub.A/z|J|; T = 1/z|J|) and (D.sub.B/z|J|; T = 1/z|J|) planes for various values of the ratio R = K/|J| (R > 0). Our phase diagrams show both first- and second-order transitions, as well as tricritical points. It is evident that the system can exhibit single and double compensation temperatures. Finally, the temperature dependencies of the total and sublattice magnetizations present a few outstanding features.