The effective-field theory studies of critical phenomena in a mixed spin-1 and spin-2 Ising model on honeycomb and square lattices (original) (raw)
Related papers
The effective-field study of a mixed spin-1 and spin-5/2 Ising ferrimagnetic system
Physica Scripta, 2009
An effective-field theory with correlations is developed for a mixed spin-1 and spin-5/2 Ising ferrimagnetic system on the honeycomb (δ = 3) and square (δ = 4) lattices in the absence and presence of a longitudinal magnetic field. The ground-state phase diagram of the model is obtained in the longitudinal magnetic field (h) and a single-ion potential or crystal-field interaction ( ) plane. We also investigate the thermal variations of the sublattice magnetizations, and present the phase diagrams in the ( /|J |, k B T /|J |) plane. The susceptibility, internal energy and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the absence and presence of the applied longitudinal magnetic field. Moreover, the system undergoes second-and first-order phase transition; hence, the system gives a tricritical point. The system also exhibits reentrant behavior.
An effective-field theory with correlations is developed for a mixed spin-1 and spin-5/2 Ising ferrimagnetic system on the honeycomb (δ = 3) and square (δ = 4) lattices in the absence and presence of a longitudinal magnetic field. The ground-state phase diagram of the model is obtained in the longitudinal magnetic field (h) and a single-ion potential or crystal-field interaction ( ) plane. We also investigate the thermal variations of the sublattice magnetizations, and present the phase diagrams in the ( /|J |, k B T /|J |) plane. The susceptibility, internal energy and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the absence and presence of the applied longitudinal magnetic field. Moreover, the system undergoes second-and first-order phase transition; hence, the system gives a tricritical point. The system also exhibits reentrant behavior.
Chinese Physics B, 2011
The phase diagrams in the mixed spin-3/2 and spin-2 Ising system with two alternative layers on a honeycomb lattice are investigated and discussed by the use of the effective-field theory with correlations. The interaction of the nearest-neighbour spins of each layer is taken to be positive (ferromagnetic interaction) and the interaction of the adjacent spins of the nearest-neighbour layers is considered to be either positive or negative (ferromagnetic or antiferromagnetic interaction). The temperature dependence of the layer magnetizations of the system is examined to characterize the nature (continuous or discontinuous) of the phase transitions and obtain the phase transition temperatures. The system exhibits both second-and first-order phase transitions besides triple point (T P ), critical end point (E), multicritical point (A), isolated critical point (C) and reentrant behaviour depending on the interaction parameters. We have also studied the temperature dependence of the total magnetization to find the compensation points, as well as to determine the type of behaviour, and N-type behaviour in Néel classification nomenclature existing in the system. The phase diagrams are constructed in eight different planes and it is found that the system also presents the compensation phenomena depending on the sign of the bilinear exchange interactions.
Revista Mexicana de Fisica
We used a Monte Carlo simulation to analize the magnetic behavior of Ising model of mixed spins S A i = ±3/2, ±1/2 and σ B j = ±5/2, ±3/2, ±1/2, on a square lattice. Were studied the possible critical phenomena that may emerge in the region around the multiphase point (D/|J1| = −3, J2/|J1| = 1) and the dependence of the phase diagrams with the intensities of the anisotropy field of single ion (D/|J 1 |) and the ferromagnetic coupling of exchange spin S A i (J 2 /|J 1 |). The system displays first order phase transitions in a certain range of the parameters of the Hamiltonian, which depend on D/|J 1 | and |J 2 /|J 1 |. In the plane (D/|J 1 |, k B T /|J 1 |), the decrease of |D/|J 1 ||, implies that the critical temperature, T c , increases and the first order transition temperature, T t , decreases. In the plane (J2/|J1|, kBT /|J1|), Tc increases with the increasing of J2/|J1|, while that Tt decreases.
Physical Review B, 2004
Magnetic properties of a mixed spin-1/2 and spin-1 Ising model on honeycomb lattice are exactly investigated within the framework of generalized star-triangle mapping transformation. The particular attention is focused on the effect of uniaxial and biaxial crystal-field anisotropies that basically influence the magnetic behaviour of the spin-1 atoms. Our results for the basic thermodynamic quantities, as well as the dynamical time-dependent autocorrelation function indicate the spin tunneling between the | + 1 and | − 1 states in the magnetically ordered phase.
Physica A: Statistical Mechanics and its Applications, 2005
Magnetic properties of a mixed spin-1/2 and spin-3/2 Ising model on honeycomb lattice are investigated within the framework of an exact star-triangle mapping transformation. The particular attention is focused on the effect of uniaxial and biaxial crystal-field potentials that basically influence a magnetic behavior of the spin-3/2 atoms. Our results for basic thermodynamic quantities as well as dynamical time-dependent autocorrelation function indicate a spin tunneling between |± 3 2 and |∓ 1 2 states in two different magnetically ordered phases OP 1 and OP 2 , respectively.
Critical behavior of the classical spin-1 Ising model for magnetic systems
AIP Advances, 2022
In this work, the critical properties of the classical spin-1 Ising Hamiltonian applied to magnetic systems characterized by the first-neighbors biquadratic exchange, the anisotropy and the external magnetic field contributions are theoretically investigated. The first-neighbors bilinear exchange interaction is set equal to zero. For magnetic systems the bicubic exchange interaction must be set equal to zero as it would break the time-reversal invariance of the exchange Hamiltonian. To determine the critical behavior, the spin-1 Ising Hamiltonian is mapped onto the spin-1/2 Ising Hamiltonian by using the Griffith’s variable transformation. The critical surface of a 2D square magnetic lattice is determined in the parameter space as a function of the magnetic parameters and the phase transition occurring across it is quantitatively discussed by calculating, for each spin, the free energy and the magnetization. The free energy of the 2D square magnetic lattice, described via the three-...
The critical behavior of the mixed spin-1 and spin-2 Ising ferromagnetic system on the Bethe lattice
Physica A-statistical Mechanics and Its Applications, 2005
The phase diagrams of the mixed spin-1 and spin-2 Blume-Capel Ising ferromagnetic system ðJ40Þ with two crystal-field interactions, D A for spin-1 and D B for spin-2, is studied on the Bethe lattice by using the exact recursion equations. The exact expressions of the orderparameters for the sublattices with spin-1 and spin-2, and the Curie temperature and the free energy of the system are obtained in terms of the recursion relations. The phase diagrams on the ðkT c =J; D A =JÞ and ðkT c =J; D B =JÞ planes are studied for selected values of D B =J and D A =J; respectively, for the coordination numbers q ¼ 3; 4; and 6. Besides the second-order phase transition lines, the lines of the first-order phase transitions terminating either at a tricritical point or at an isolated critical point are found. r
An effective-field study of the mixed spin-1 and spin- Ising ferrimagnetic system
Journal of Magnetism and Magnetic Materials, 2002
An effective-field theory with correlations, that correctly incorporates the single-site kinematic relations of the spin operators, is applied to the mixed spin-1 and spin-3 2 Ising system with different single-ion anisotropies. The phase diagrams are investigated numerically for the square and simple cubic lattices and results in some aspects are crucially different to those obtained by using an approximate Van der Waerden identity for spin-3 2 as well as in the case of the honeycomb lattice. The thermal dependence of the magnetization is studied, and the existence and dependence of a compensation point on single-ion anisotropies is also investigated for the square lattice.