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The ferrimagnetic-ferromagnetic-ferrimagnetic quaternary alloy consisting of the spins S i A = 1 , S j B = 3 / 2 , S j C = 5 / 2 and S j D = 2 in the form of A B p C q D r with B, C and D being the possible nearest-neighbors of A with the probabilities p, q and r, respectively, is investigated in terms of the mean field theory (MFT) based on the Bogoliubov inequality for free energy. The thermal behaviors of magnetizations belonging to the individual spins and total magnetization are examined in detail to map the possible phase diagrams on various planes. It was found that the model only exhibits second-order phase transitions in addition to one compensation temperature for appropriate values of the system parameters. In order to support the existence of the compensation temperatures, we have also carried out the Monte Carlo (MC) simulations and an agreement was shown with the predicted result of the MFT approach. We have also analyzed the effects of the bilinear interaction parameter between type-A atoms J A A and the exchange interaction parameter ratio R = J A X / | J A B | ( J A X is the bilinear interaction parameter between type-A atoms and type-X atoms with X = C or D) on compensation temperatures. Our findings are compared to those reported in the literature and suitable agreements are observed. [ABSTRACT FROM AUTHOR]

The effects of bimodal random crystal field and trimodal magnetic field distributions on the order parameters, i.e., magnetization and quadrupole moments, susceptibility and hysteresis properties of the spin-1 Blume-Capel model are investigated. The lowest approximation of the cluster variation method was used. For the distributions of crystal field and magnetic field, two nodes and three nodes distributions were chosen, respectively, with the probabilities q and p. Exploiting the variation of the order parameters and susceptibility as functions of temperature and crystal field, it was found that they exhibit either continuous or discontinuous phase transitions, i.e., first- or second-order, respectively. The model also presents the re-entrant behaviour for some values of our system parameters. Under the constraint of magnetic field and specific values of the system parameters, two, four and six hysteresis loops have been observed. [ABSTRACT FROM AUTHOR]

In this paper, the effects of the longitudinal D z and the transverse D x crystal fields on the mixed spin- (1 2 , 3 2) Ising–Heisenberg model have been studied. The thermodynamic properties of the model are obtained by using a new approach of the mean field approximation (MFA). The thermal variations of the order-parameters and the total magnetic susceptibility of the model are carefully investigated to obtain the phase diagrams on the (D x / J , k B T / J) planes for z = 3 and on the (D z / J , k B T / J) planes for z = 3 , 4 and 6. The existence of compensation temperatures between the sublattice magnetizations, T comp , M , and the two components of the quadrupole moments, T comp , Q , are observed. Our results are compared with other existing works in the literature and reliable agreements are found. [ABSTRACT FROM AUTHOR]

We use theoretical and numerical calculations in the framework of the effective-field theory to examine the rigorous effects of the crystal field interactions of the mixed spin-2 and spin- Blume-Capel model on the honeycomb lattice in the presence of an external magnetic field. The ground state phase diagram has been constructed. Thermal changes of the order parameters and other thermodynamic quantities of interest and their influence on the phase diagrams of the model have been thoroughly investigated. The system shows very interesting critical properties including continuous and discontinuous phase transitions, tricritical points and compensation temperatures which are revealed in specific ranges of the parameters space. Our numerical findings are compared to those obtained by other methods and reliable agreements are recovered. [ABSTRACT FROM AUTHOR]

The mixed spin-1 and spin-Blume–Capel model is investigated on the Bethe lattice in the presence of an external magnetic fieldh. 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/|J|,D/|J|) plane whenq= 3, 4 and 6. The model exhibits first-order and second-order phase transitions and tricritical points where transition lines are connected. Besides these transitions, the system also shows compensation points for appropriate values of the model parameters. [ABSTRACT FROM PUBLISHER]