The dynamic phase transitions are studied in the spin‐2 Ising model under a time‐dependent oscillating magnetic field by using the effective‐field theory with correlations. The effective‐field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first‐ or second‐order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.
The dynamic phase transitions are studied in the spin‐2 Ising model under a time‐dependent oscillating magnetic field by using the effective‐field theory with correlations. The effective‐field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first‐ or second‐order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.
We calculate the dynamic phase transition (DPT) temperatures and present the dynamic phase diagrams in the kinetic mixed spin-1/2 and spin-5/2 Ising model under the presence of a time-dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the set of mean-field dynamic equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The DPT points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain four fundamental phases and three coexistence or mixed phases, which strongly depend on interaction parameters. The phase diagrams are discussed and a comparison is made with the results of the other mixed spin Ising systems.
We study the nonequilibrium aspects of the kinetics of a mixed spin-1 and spin-2 Ising system including the biquadratic nearest-neighbor pair interaction ( K ) and crystal-field interaction ( D ) under the presence of a time-dependent oscillating external magnetic field within a mean-field approach. In particular, we calculate the dynamic phase transition (DPT) temperatures and present dynamic phase diagrams. The set of mean-field dynamic equations is obtained by employing Glauber transition rates. We investigate the time variations of average order parameters to find the phases in the system. We also study the thermal behavior of the dynamic order parameters to characterize the nature (continuous or discontinuous) of the phase transitions and obtain the DPT points. The dynamic phase diagrams are presented in three different planes. Phase diagrams contain disordered (d), ferrimagnetic (i), antiquadrupolar or staggered (a) phases, and four coexistence or mixed phase regions, namely i+d, i+a, i+a+d and a+d mixed phases, that strongly depend on interaction parameters.
The dynamic phase transition (DPT) temperatures and the dynamic phase diagrams are obtained for spin-1/2 Ising system under the presence of a time-dependent oscillating external magnetic field using the method that was purposed by Meijer and Edwards [ANNALS of PHYSICS, 54, 240 (1969)] within the framework of the Bethe or constant coupling theory. The time variation of magnetization is investigated to find the phases in the system. Thermal behavior of the average magnetization is studied to characterize the nature (continuous and discontinuous) of transitions and to obtain the dynamic phase transition temperatures. The DPT temperatures are found always a second-order; hence there can be no tricritical point separating lines of first- and second-order dynamic phase transitions. This result agrees with the dynamic Monte-Carlo (MC) simulations of a two-dimensional kinetic spin-1/2 Ising model in an oscillating external magnetic field.
Nonequilibrium magnetic properties in a two-dimensional kinetic mixed spin-2 and spin-5/2 Ising system in the presence of a time-varying (sinusoidal) magnetic field are studied within the effective-field theory (EFT) with correlations. The time evolution of the system is described by using Glauber-type stochastic dynamics. The dynamic EFT equations are derived by employing the Glauber transition rates for two interpenetrating square lattices. We investigate the time dependence of the magnetizations for different interaction parameter values in order to find the phases in the system. We also study the thermal behavior of the dynamic magnetizations, the hysteresis loop area, and dynamic correlation. The dynamic phase diagrams are presented in the reduced magnetic field amplitude and reduced temperature plane and we observe that the system exhibits dynamic tricritical and reentrant behaviors. Moreover, the system also displays a double critical end point (B), a zero-temperature critical point (Z), a critical end point (E), and a triple point (TP). We also performed a comparison with the mean-field prediction in order to point out the effects of correlations and found that some of the dynamic first-order phase lines, which are artifacts of the mean-field approach, disappeared.
We studied the dynamic magnetic properties such as dynamic phase transitions, dynamic compensation temperatures, and dynamic phase diagrams in the spin-7/2 multilayer Ising system under an oscillating external magnetic field The system was simulated in the mean-field approximation using a Glauber type stochastic dynamic. The mean sublattice magnetizations’ time variations were examined to determine the system's dynamic phases. The thermal behavior of dynamic sublattice magnetizations was investigated to determine the type of dynamic phase transitions (first- or second-order) and to obtain the dynamic compensation temperatures. P−,Q−,R−,S−, and L−type compensating behaviors were seen in various types of magnetization curves. The phase diagrams are calculated in J−T, T−h, and d−T planes, for different values of the Hamiltonian parameters. The p, i, f1/2, f7/2, af7/2, and af1/2 fundamental phases, as well as the i + p, i + f1/2, af1/2 + p, af7/2 + p and i + af1/2 mixed phases. The system illustrated one, two, or three dynamic critical points (•) and E, TP, Z, and B special points.
Employing a mean-field approach, we study the stationary states of the kinetic spin-5/2 Blume–Emery–Griffiths (BEG) model under the presence of a time-varying (sinusoidal) magnetic field by using the Glauber-type stochastic dynamics. We employ the Glauber transition rates to construct the set of dynamic mean-field equations. We investigate the time variation in average order parameters to find the phases in the system, and the thermal behavior of the dynamic order parameters to characterize the nature (continuous or discontinuous) of the dynamic phase transtions and to the dynamic phase transition temperature. The dynamic phase diagrams are presented in three different planes. The phase diagrams contain the ferromagnetic-5/2, the ferromagnetic-3/2, the ferromagnetic-1/2, the ferroquadrupolar, and disordered fundamental phases. They also include the nine coexisting or mixed phases composed of binary and ternary combinations of fundamental phases that strongly depend on the interaction parameters. The phase diagrams display the critical end point, double critical end point, triple point, quadruple point, and one, two, or three special points and the dynamic tricritical point that depends on the interaction parameters.