Tricritical behavior of Ising metamagnet in both external longitudinal and transverse fields

Sousa

2013

Phys. Scr.

In this paper, we study the critical behavior of the three-dimensional antiferromagnetic Ising model in both uniform longitudinal (H ) and transverse ( ) magnetic fields. Using the effective field theory (EFT) with finite cluster N = 1 spin (EFT) we calculate the phase diagrams in the H -T , -T and -H planes for a simple cubic lattice. We have only found second-order phase transitions for all values of fields and reentrant behavior was observed at low temperature.

Section: Resultsmentioning

confidence: 53%

Reentrance in the phase diagrams of the transverse Ising antiferromagnet in the presence of the longitudinal magnetic field on a simple cubic lattice

Sousa

2013

Phys. Scr.

“…We hope that the present method can be employed for more complex models, for instance, the generalization of the model to treat three-dimensional lattice, where multicritical points in the phase diagrams are observed in MFT [40,41]. This reentrant behavior does not occur at low temperature and that was found in a classical approach (MFA) that does not give the correct description of the ground-state phase diagram, with the presence of reentrant behavior near h = h c and the quantum critical point δ c /z = 1.00 is independent of the coordination number z [33,34].…”

Section: Resultsmentioning

confidence: 99%

Phase diagrams of the transverse Ising antiferromagnet in the presence of the longitudinal magnetic field

Physica A: Statistical Mechanics and its Applications

Sousa

2013

In this paper we study the critical behavior of the two-dimensional antiferromagnetic Ising model in both uniform longitudinal (H) and transverse (Ω) magnetic fields. Using the effective-field theory (EFT) with correlation in single site cluster we calculate the phase diagrams in the H − T and Ω − T planes for the square (z = 4) lattices. We have only found second order phase transitions for all values of fields and reentrant behavior was not observed.

Multicritical behavior of the two-dimensional transverse Ising metamagnet in a longitudinal magnetic field

Nascimento

Pacobahyba

Physica A: Statistical Mechanics and its Applications

et al. 2017

Magnetic phenomena of the superantiferromagnetic Ising model in both uniform longitudinal (H) and transverse (Ω) magnetic fields are studied by employing a mean-field variational approach based on Peierls-Bogoliubov inequality for the free energy. A single-spin cluster is used to get the approximate thermodynamic properties of the model. The phase diagrams in the magnetic fields and temperature (T ) planes, namely, H − T and Ω − T , are analyzed on an anisotropic square lattice for some values of the ratio α = J y /J x , where J x and J y are the exchange interactions along the x and y directions, respectively. Depending on the range of the Hamiltonian parameters, one has only second-order transition lines, only first-order transition lines, or first-and second-order transition lines with the presence of tricritical points. The corresponding phase diagrams show no reentrant behavior along the first-order transition lines at low temperatures. These results are different from those obtained by using Effective Field Theory with the same cluster size.