The critical behavior of the three-dimensional antiferromagnetic Heisenberg model with nearest-neighbor (J) and next-to-nearest-neighbor (J 1) interactions is studied by the replica Monte Carlo method. The first-order phase transition and pseudouniversal critical behavior of this model are established for a small lattice in the interval R = |J 1/J| = 0–0.115. A complete set of the main static magnetic and chiral critical indices is calculated in this interval using the finite-dimensional scaling theory.
We study by large-scale Monte Carlo simulation the
RP3 model, which can be regarded as an effective low-energy model of a triangular lattice Heisenberg antiferromagnet.
Z2 vortices appear as elementary excitations in the triangular lattice Heisenberg antiferromagnet. Such
Z2 vortices are ubiquitous in other frustrated Heisenberg spin systems that have noncollinear long-range orders. In this study, we investigate a possible topological phase transition driven by the binding--unbinding of
Z2 vortices. By extracting important degrees of freedom, we map a frustrated spin system to an effective
RP3 model. From large-scale Monte Carlo simulation, we obtain an order parameter and a correlation length of up to
L=16384. Concerning the existence of a
Z2-vortex transition, by extrapolating the order parameter to the thermodynamics limit assuming the
Z2-vortex transition, we obtain a finite transition temperature as
Tv/J~≃0.25. Our estimate of the correlation length at
Tv is much larger than
L=16384, which is beyond the previous estimate obtained with the triangular lattice Heisenberg model.
The critical behavior and phase transitions (PT) of the three-dimensional antiferromagnetic Heisenberg model on a layered triangular lattice with nearest-neighbor (J) and next-to-nearest neighbor (J1) interactions is studied by the replica Monte Carlo method. The first order phase transition has been revealed in the studied model based on the histogram method of processing data of the Monte Carlo for systems with large linear dimensions. Shown that the system exhibits the pseudouniversal critical behavior in the case of small lattices.
Phase transitions and critical properties in the antiferromagnetic Heisenberg model on a layered cubic lattice with allowance for intralayer next nearest neighbor interactions have been studied using the replica Monte Carlo algorithm. The character of phase transitions has been analyzed using the histogram method and the Binder cumulant method. It has been found that a transition from the collinear to paramagnetic phase in the model under study occurs as a second order phase transition. The statistical critical exponents of the specific heat α, susceptibility γ, order parameter β, and correlation radius ν, as well as the Fisher index η, have been calculated using the finite-size scaling theory. It has been shown that the three-dimensional Heisenberg model on the layered cubic lattice with allowance for the next nearest neighbor interaction belongs to the same universality class of the critical behavior as the antiferromagnetic Heisenberg model on a layered triangular lattice.
The phase transitions (PTs) and critical properties of the antiferromagnetic Ising model on a layered (stacked) triangular lattice have been studied by the Monte Carlo method using a replica algorithm with allowance for the next-nearest-neighbor interactions. The character of PTs is analyzed using the histogram technique and the method of Binder cumulants. It is established that the transition from the disordered to paramagnetic phase in the adopted model is a second-order PT. Static critical exponents of the heat capacity (α), susceptibility (γ), order parameter (β), and correlation radius (ν) and the Fischer exponent η are calculated using the finite-size scaling theory. It is shown that (i) the antiferromagnetic Ising model on a layered triangular lattice belongs to the XY universality class of critical behavior and (ii) allowance for the intralayer interactions of next-nearest neighbors in the adopted model leads to a change in the universality class of critical behavior.
The phase transitions and critical properties of the three-dimensional stacked triangular-lattice Ising antiferromagnet in a magnetic field are studied using the replica Monte Carlo method. The nature of the phase transitions is analyzed on the basis of the histogram method. It is established that a second-order transition occurs in the field range of 0 ≤ h ≤ 6. At a high field, the degeneracy of the ground state is lifted and the phase transition is smeared. Depending on the magnitude of the magnetic field, disordered, partially ordered, and completely ordered phases are observed.