Within the framework of the effective field theory (EFT) and cutting approximation, the spin-1 transverse random crystal field Ising model is investigated for a square lattice. We discuss in detail the influence of transverse random crystal field concentration and crystal field ratio on the phase diagram and magnetization behavior. We give phase diagrams in T-Dx space and magnetization curves in m-T space. Under crystal field dilution condition, there exists the peak value of critical temperature in the direction of negative crystal field and reentrant phenomena in the direction of positive critical field. While choosing crystal field ratio α=+0.5 and α=-0.5, the range of magnetic ordered phase shrinks. In particular, we found, with decreasing of concentration, the peak value of critical temperature undergoes a crossover from negative to positive direction of transverse crystal field when the ratio α=-0.5. The magnetization behaviors have apparent difference for a given negative crystal field value when the crystal field ratio is different. We give a meaningful comparison with the results of Ising model with longitudinal dilution crystal field.
Abstract:Within effective field theory (EFT), the critical properties of a random transverse crystal field Ising model with bond dilution are studied on a square lattice. Under both weak and strong bond dilution conditions, we consider three cases (α = 0 ±0 5) of a transverse crystal field ratio, obtaining global phase diagrams in T − D x space for changes in the random transverse crystal field concentration. The phase diagrams obtained for a weak bond dilution are very similar in shape to those of pure bond but with decreases in corresponding ordered phases and critical values. However, the phase diagrams for a strong bond dilution exhibit varieties, including a change in reentrant phenomenon, the occurrence of transverse crystal field degeneration, and the opposite direction crossover of temperature peak value.
PACS
We study the ferromagnetic properties of spin-1 system, which is considered in the frame of the bond-dilution and random positive or negative anisotropy Blume–Capel model in the effective field theory and a cutting approximation. The investigation of phase diagrams displays some rich properties of the trajectory of tricritical point, reentrant phenomena at low temperatures. Under certain both bond concentrations and random negative anisotropy, there are new transition lines of double tricritical points. So special emphasis is placed on the influence of the bond dilution and random anisotropy on phase diagrams. The magnetizations of the system are also discussed. Some results have not been revealed in previous reports.
The magnetic properties of bond-diluted nearest-neighbor interaction mixed spin-1/2 and spin-1 Ising ferrimagnetic spin system with different transverse fields are investigated within the framework of the finite cluster approximation (FCA). Particular emphasis is given to the square lattice with coordination number Z = 4 for which magnetizations are obtained. The interactions Jij are assumed to be independent random variable with distribution P(Jij) = pS(Jij -J) + (l-p)S(Jij), where J < 0. If bond concentration p varies in the certain ranges, we find that the compensation temperature is obtained for the values of the different transverse fields fli/2 and O-i in a restricted region. We obtain the vaJues of the critical different transverse fields and critical bond concentration in this paper.
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