Guozhu Wei

Magnetic properties of a mixed spin-12 and spin-32 transverse Ising model with a crystal field

The mixed spin-12 and spin-32 transverse Ising model with a crystal field is studied within the framework of the effective-field theory with correlations. The phase diagrams and thermal behaviors of magnetizations are investigated numerically for the honeycomb (z=3). The results show that there is no tricritical point for the system.

A ferromagnetic or ferrimagnetic bilayer system with a transverse crystal field

Abstract Phase diagrams of a ferromagnetic or ferrimagnetic bilayer system consisting of two magnetic monolayers (A and B) with different spins ( S A = 1 2 , and S B =1, 3 2 ) and different interaction constants coupled together in a transverse crystal field are studied. Within the framework of the effective-field theory with correlations, the effects of the transverse crystal field in the monolayer B on the magnetic properties are investigated in detail for the square lattice. We have obtained some interesting results that may potentially be related to experimental work on rare-earth/transition-metal multilayer films.

Compensation temperatures of mixed spin-2 and spin-5/2 ferrimagnetic system with interlayer coupling; a study of a molecular-based magnet

Compensation points of layer system consisting of mixed spin-2 and spin-5/2 ferrimagnetic honeycomb lattice layers which are coupled together with two kinds of positive interlayer coupling are examined by the use of the effective-field theory with correlations (EFT). In particular, the effects of interlayer coupling and a positive crystal-field constant of the spin-2 ions on the compensation temperature are investigated, in order to clarify the characteristic behavior of the temperature dependence of the total magnetization M. This is related to the experimental works of a molecular-based magnetic multilayer film, N(n-C(4)H(9))(4)Fe(II)Fe(III)(C(2)O(4))(3). A comparison is made between the results in this paper and those in a previous work obtained by using Monte-Carlo simulations

Magnetic properties of ground state in diluted mixed-spin Ising ferrimagnetic systems

The magnetic properties of the ground state in diluted mixed spin-1/2-spin-1 Ising ferrimagnetic (J < 0) systems with a negative crystal-field (D < 0) interaction are studied by using the effective-field theory with correlations. The effects of diluting z = 3 and 4 systems are given in phase diagram and magnetization curves. For the z = 4 system both the second-order and the first-order phase transitions exist and for z = 3 system only second-order phase transition exists

Antiresonance and bound states in the continuum in electron transport through parallel-coupled quantum-dot structures

In this paper we make a theoretical study of electron transport through a multi-quantum-dot system, in which the peripheral quantum dots of a one-dimensional chain are embodied in the two arms of an Aharonov-Bohm interferometer. It is found that, in the absence of magnetic flux, all the even molecule states of odd-numbered quantum-dot structures decouple from the leads and in even-numbered quantum-dot systems all the odd molecule states decouple from the leads, which indicates the formation of remarkable bound states in the continuum. Meanwhile, what is interesting is that apparent antiresonance occurs in electron transport through this structure, the positions of which are accordant with all even (odd) eigenenergies of the sub-molecule of the even (odd)-numbered quantum dots without the peripheral dots. All these results are efficiently modified by the presence of magnetic flux through this system.

Phase diagrams and tricritical behavior of spin-2 ising model with a transverse crystal field

Within the framework of the effective-field theory with correlations, the ferromagnetic spin-2 Ising model with a transverse crystal field on honeycomb, square and simple cubic lattices is studied. We have investigated the effect of the transverse crystal field on the phase diagrams, magnetization, quadrupolar moments, internal energy and specific heat of the system. The tricritical phenomena have been observed in our system.

Phase diagrams and tricritical behavior in spin-1 Ising Model with biaxial crystal-field on honeycomb lattice

Within the framework of the effective-field theory with correlations, the ferromagnetic spin-1 Ising model with biaxial crystal-field on honeycomb lattice is studied. The effects of the biaxial anisotropy parameters on the phase diagrams, tricritical points are investigated. The results show that the tricritical points and reentrant phenomena may appear in certain ranges of the two transverse crystal-field interactions.

Effect of a crystal field on phase transitions in a spin-3/2 transverse Ising model

Abstract The spin- 3 2 transverse Ising model with the presence of a crystal field is studied within the framework of the effective-field theory with correlations. The phase diagrams are investigated numerically for the honeycomb (z=3), square (z=4) and simple cubic (z=6) lattices.

Effects of biaxial crystal-field on spin-3/2 honeycomb lattice

The method of the effective-field theory with self-spin correlations and the differential operator technique is used to study the magnetic properties of the spin-3/2 Ising model with biaxial crystal-field on the honeycomb lattice. The effects of a biaxial crystal-field described by two uniaxial anisotropy parameters Dx and Dy on the phase transition and specific heat and susceptibility are studied analytically and numerically. Some characteristic phenomena are found in the system such as tricritical behavior depending sensitively on the strength of the biaxial crystal-field.

Magnetic Properties of Transverse Ising Model under a Time Oscillating Longitudinal Field

A transverse Ising spin system, in the presence of time-dependent longitudinal field, is studied by the effective-field theory (EFT). The effective-field equations of motion of the average magnetization are given for the simple cubic lattice (Z = 6) and the honeycomb lattice (Z = 3). The Liapunov exponent lambda is calculated for discussing the stability of the magnetization and it is used to determine the phase boundary. The dynamic phase transition diagrams in h(0)/ZJ -Gamma/ZJ plane and in h(0)/ZJ - T/ZJ plane have been drawn, and there is no dynamical tricritical point on the dynamic phase transition boundary. The effect of the thermal fluctuations upon the dynamic phase boundary has been discussed