Mixed spin-2 and spin-52 Blume–Capel model

The influence of increasing the coordination number q   on the phase diagrams of the mixed spin-2 and spin-52 Blume–Capel Ising ferrimagnetic system with two crystal-field interactions, DADA for spin-2 and DBDB for spin-52, is investigated on the Bethe lattice by using the exact recursion equations. The phase diagrams are obtained for the case with equal crystal field strengths when q=3q=3, 4 and 6 on the (kT/|J|,D/|J|kT/|J|,D/|J|) planes and for the case with unequal crystal field strengths on the (kT/|J|,DA/|J|kT/|J|,DA/|J|) and (kT/|J|,DB/|J|kT/|J|,DB/|J|) planes for various values of DB/|J|DB/|J| and DA/|J|DA/|J|, respectively, for q=4q=4 and 6. Besides the second-order lines, the model presents three types of first-order phase transition lines; one of them ends on the compensation lines (q=3q=3), the other one ends at a critical end point (q=4q=4) and last one terminates at a tricritical point (q=6q=6) for the case with equal crystal field strengths. In this case we have also observed up to four compensation temperatures when q=6q=6. Besides the second-order, tricritical and compensation lines, the system presents two types of the first-order lines one of them ending at a tricritical point and the other one ending at an isolated point when unequal crystal field values are taken.