Magnetic behavior of a mixed spin-1 and spin- 7 BlumeÀCapel 2 model on the Bethe lattice in the presence of an applied magnetic field

Abstract

The mixed spin-1 and spin- 7 BlumeÀCapel model is investigated on the 2 Bethe lattice in the presence of an external magnetic field h. The ground- state phase diagram which may be useful to explore interesting domains of the temperature phase diagrams of the model is constructed. The order parameters, the response functions, the internal energy and the free energy are thoroughly examined in order to characterize the nature of the phase transitions and to obtain the corresponding temperatures. Then, in the absence of the magnetic field, the temperature phase diagrams are displayed in the case of equal crystal field on the (kT/jJj, D/jJj) plane when q D 3, 4 and 6. The model exhibits first-order and second-order phase tran- sitions and tricritical points where transition lines are connected. Besides these transitions, the system also shows compensation points for appropri- ate values of the model parameters.