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1.
Within the framework of an effective field approximation, the effects of single-ion anisotropy and different trimodal transverse fields of two sublattices on the critical properties of the mixed spin-1/2 and spin-1 Ising system are investigated on the simple cubic lattice. A smaller single-ion anisotropy can magnify magnetic ordering
phases and a larger one can depress magnetic ordering phase for
T-Ω1/2 space at low temperatures, while a smaller single-ion
anisotropy can hardly change the value of critical transverse field for
T-Ω1 space. On the other hand, influences of two different trimodal transverse fields concentrations on tricritical points and magnetic ordering
phases take on some interesting results in T-D space. The main reason
comes from the common action of single-ion anisotropy, different transverse
fields and two trimodal distributions. 相似文献
2.
Numerical and analytical results are presented for the magnetic ordering in a bond-diluted spin-1/2 and spin-1 mixed transverse Ising system with a single-ion anisotropy on a honeycomb lattice.Special emphsis is placed on the magnetic ordering under the bond dilution and percolation threshold.We discuss in detail the influence of transverse fields of different sublattics on the normal magnetic ordering and on the magnetic ordering induced by single-lon anisotropy.We find that the magnetic ordering of a system exhibits an explicit difference when receiving the transverse field.This phenomenon has not been revealed in previous reports. 相似文献
3.
M. Dudzinski J. Sznajd J. Zittartz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):575-579
The zero temperature phase diagram of a one-dimensional ferromagnet with cubic single ion anisotropy in an external magnetic
field is studied. The mean-field approximation and the density-matrix renormalization group method are applied. Two phases
at finite magnetic fields are identified: a canted phase with spontaneously broken symmetry and a phase with magnetization
along the magnetic field. Both methods predict that the canted phase exists even for the single-ion anisotropy strong enough
to destroy the magnetic order at zero magnetic field. In contrast to the mean-field theory, the density-matrix renormalization
group predicts a reentrant behavior for the model. The character of the phase transition at finite magnetic field has also
been considered and the critical index has been found.
Received 9 May 2000 and Received in final form 5 July 2000 相似文献
4.
A double-wall cubic metal nanotube consists of the ferromagnetic spin-1 inner shell and spin-3/2 surface shell. It is of the ferrimagnetic exchange coupling between two shells. Considering the single-ion anisotropy and transverse field exist together, the magnetization, the initial susceptibility, the internal energy and the specific heat have been investigated by using the effective-field theory with correlations. Some interesting phenomena have been found in the thermal variations of the system. Magnetization appears two or three compensation points in certain parameters. It is an unconventional ferrimagnetic behavior in the nanotube. The shapes of total magnetization and the initial susceptibility are great influenced by the surface exchange coupling, surface single-ion anisotropy and surface transverse field. Some results of nanotube may have potential applications in different research fields, such as electronics, optics, mechanics, and even biomedicine and molecular devices. 相似文献
5.
6.
Thermodynamic Properties of Random Transverse Field Mixed Spin
System in the Presence of Single-Ion Anisotropy 总被引:1,自引:0,他引:1
ZHANGYa-Nan YANShi-Lei 《理论物理通讯》2003,40(3):375-380
We study the thermodynamic properties of random transverse field mixed spin system in the presence of single-ion anisotropy on a square lattice. By making use of the effective field theory and a cutting approximation, the detailed phase diagrams are described and some interesting results are found under trimodal random transverse field distribution. A small single-ion anisotropy can magnify magnetic ordering region at low temperatures and existence of a large transverse field can assist the occurrence of reentrant phenomena. With increasing disorder, second-order phase transitions are shown to change into first-order phase transitions. The trajectory of the tricritical point in the phase space as a function of disorder is presented. These indicate a strong correlation with the corresponding to trimodal transverse field distribution. 相似文献
7.
M. Dudzinski J. Sznajd 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):745-750
The ground state properties of S
=2 ferromagnets with isotropic Heisenberg exchange (J) and single-ion cubic anisotropy (D) are studied. The perturbation theory for is used to find an effective Hamiltonian up to the fourth order for 1, 2 and 3 dimensions. It is shown that in opposition
to the MFA prediction there is the quadrupolar long range order at T
= 0 in the non-magnetic state of the system without a quadrupolar type of interaction. The effect is a consequence of the quantum
nature of the model.
Received: 19 February 1998 / Accepted: 17 March 1998 相似文献
8.
P. Fröbrich P.J. Jensen P.J. Kuntz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):477-489
The reorientation of the magnetization of a ferromagnetic monolayer is calculated with the help of many-body Green's function
theory. This allows, in contrast to other spin wave theories, a satisfactory calculation of magnetic properties over the entire
temperature range of interest since interactions between spin waves are taken into account. A Heisenberg Hamiltonian plus
a second-order uniaxial single-ion anisotropy and an external magnetic field is treated by the Tyablikov (Random Phase Approximation:
RPA) decoupling of the exchange interaction term and the Anderson-Callen decoupling of the anisotropy term. The orientation
of the magnetization is determined by the spin components (), which are calculated with the help of the spectral theorem. The knowledge of the orientation angle allows a non-perturbative determination of the temperature dependence of the effective second-order anisotropy coefficient.
Results for the Green's function theory are compared with those obtained with mean-field theory (MFT). We find significant
differences between these approaches.
Received 6 April 1999 and Received in final form 9 July 1999 相似文献
9.
10.
A linear cluster mean-field approximation is used to study the magnetic properties of the Ising ferromagnetic/antiferromagnetic superlattice, which is composed of a spin-1/2 ferromagnetic monolayer and a spin-1 antiferromagnetic monolayer with a single-ion anisotropy alternatively. By using the transfer matrix method, we calculate the magnetization and the initial magnetic susceptibility as functions of temperature for different interlayer coupling, single-ion anisotropy. We summarize the changing behaviors of the spin structure in ferromagnetic and antiferromagnetic layers and the characteristics of the corresponding magnetic susceptibilities, give the transition temperature as a function of the interlayer exchange coupling for different single-ion anisotropy, and analyze the features of the magnetization and the magnetic susceptibility. 相似文献
11.
P. Fröbrich P.J. Kuntz 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):445-455
The many-body Green's function theory developed in our previous work for treating the reorientation of the magnetization of
thin ferromagnetic films is extended to include the exchange anisotropy. This leads to additional momentum dependencies which
require some non-trivial changes in the formalism. The theory is developed for arbitrary spin values S and for multilayers. The effects of the exchange anisotropy and the single-ion anisotropy, which was treated in our earlier
work, on the magnetic properties of thin ferromagnetic films are compared.
Received 31 October 2002 Published online 7 May 2003 相似文献
12.
P. Fröbrich P.J. Jensen P.J. Kuntz A. Ecker 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):579-594
The field-induced reorientation of the magnetization of ferromagnetic films is treated within the framework of many-body Green's
function theory by considering all components of the magnetization. We present a new method for the calculation of expectation
values in terms of the eigenvalues and eigenvectors of the equations of motion matrix for the set of Green's functions. This
formulation allows a straightforward extension of the monolayer case to thin films with many layers and for arbitrary spin
and moreover provides a practicable procedure for numerical computation. The model Hamiltonian includes a Heisenberg term,
an external magnetic field, a second-order uniaxial single-ion anisotropy, and the magnetic dipole-dipole coupling. We utilize
the Tyablikov (RPA) decoupling for the exchange interaction terms and the Anderson-Callen decoupling for the anisotropy terms.
The dipole coupling is treated in the mean-field approximation, a procedure which we demonstrate to be a sufficiently good
approximation for realistic coupling strengths. We apply the new method to monolayers with spin and to multilayer systems with S=1. We compare some of our results to those where mean-field theory (MFT) is applied to all interactions, pointing out some
significant differences.
Received 19 June 2000 and Received in final form 2 August 2000 相似文献
13.
14.
Hai-Jun Wang Yuan Chen Liang-Jie Fu Rui-Na Lin Chuang-Chuang Song 《Journal of magnetism and magnetic materials》2009,321(12):1904-1908
One-dimensional single-ion anisotropic ferromagnet with spin-1 is investigated by means of Green's function treatment in this paper. The model Hamiltonian includes a Heisenberg ferromagnetic term, an external magnetic field, and a second-order single-ion anisotropy. The magnetic properties of the system are treated by the random phase approximation for the exchange interaction term and the Anderson-Callen approximation for the anisotropy term. Our paramagnetic results are in agreement with the other theoretical results. 相似文献
15.
A nanoisland consists of center spin-5/2 and perimeter spin-3/2 atoms, which is described by transverse Ising model with single-ion anisotropy. Magnetic behaviors of the nanoisland are studied by the effective-field theory with correlations and the differential operator technique. The formulas of the magnetization and the phase transition of the system are given. The numerical results of the phase transition, the magnetization, the initial susceptibility and the internal energy have been discussed. Some interesting phenomena, such as a new reentrant, are found. Namely there are multitransition temperatures dependent on competition among the single-ion anisotropies, the transverse field and the interlayer coupling. These results can provide some guidance to structure design in the nanoislands. 相似文献
16.
A multilayer and multisublattice cubic nanowire is studied based on a shell/core and the effective-field theory. The formulas of the longitudinal and transverse magnetization for each sublattice of the nanowire are given. The surface parameters have intense effects on the magnetizations and phase diagrams (phase transition temperatures and compensation temperatures) of the system. Two compensation points do exist for certain values of the surface transverse field, the surface single-ion anisotropy and the surface exchange coupling in the system. This interesting phenomenon may be potential applications in information storage technology. 相似文献
17.
F. Dugain M. de Boissieu K. Shibata R. Currat T.J. Sato A.R. Kortan J.-B. Suck K. Hradil F. Frey A.P. Tsai 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):513-516
The dynamics of the decagonal AlNiCo phase has been investigated on a single-grain quasicrystalline sample using inelastic
neutron scattering. The decagonal structure can be viewed as a periodic stacking of quasiperiodic planes. The anisotropy between
the modes propagating in the periodic and quasiperiodic directions is found to be much weaker than theoretically predicted.
A strong resonance splitting is observed at an energy transfer of 15 meV for transverse modes polarized in the quasiperiodic
plane.
Received: 18 November 1998 / Accepted: 27 November 1998 相似文献
18.
利用行波解法,研究了考虑交换各向异性和单离子各向异性的一维铁磁链,得出椭圆函数波解和孤子解,并讨论了单离子各向异性对椭圆函数波和孤子的影响.研究表明:单离子各向异性对一维铁磁链中椭圆函数波和孤子的激发及其稳定性有显著影响.单离子各向异性不利于易轴铁磁链中椭圆函数波和孤子解的激发,但有利于它们的稳定;而在易平面铁磁链中,单离子各向异性使椭圆函数波和孤子激发变得容易,但不利于它们的稳定.此外,还讨论了单离子各向异性对一维各向同性铁磁链中的孤子激发具有的影响.
关键词:
各向异性
单离子各向异性
孤子
铁磁链 相似文献
19.
J. Stre?ka M. Hagiwara M. Jaš?ur S. Kimura K. Kindo 《Physica B: Condensed Matter》2008,403(18):3146-3153
The magnetization process of the spin-1 Heisenberg dimer model with the uniaxial or biaxial single-ion anisotropy is particularly investigated in connection with recent experimental high-field measurements performed on the single-crystal sample of the homodinuclear nickel(II) compound [Ni2(Medpt)2(μ-ox)(H2O)2](ClO4)2·2H2O (Medpt=methyl-bis(3-aminopropyl)amine). The results obtained from the exact numerical diagonalization indicate a striking magnetization process with a marked spatial dependence on the applied magnetic field for arbitrary but finite single-ion anisotropy. It is demonstrated that the field range, which corresponds to an intermediate magnetization plateau emerging at a half of the saturation magnetization, basically depends on a single-ion anisotropy strength as well as a spatial orientation of the applied field. The breakdown of the intermediate magnetization plateau is discussed at length in relation to the single-ion anisotropy strength. 相似文献
20.
M. Holtschneider W. Selke 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(2):147-154
Classical uniaxially anisotropic Heisenberg and XY antiferromagnets
in a field along the easy axis on a square lattice
are analysed, applying ground state
considerations and Monte Carlo techniques. The models are known to
display antiferromagnetic and spin-flop phases. In the Heisenberg
case, a single-ion anisotropy is added to the XXZ antiferromagnet,
enhancing or competing with the uniaxial exchange anisotropy. Its
effect on the stability of non-collinear structures of biconical
type is studied. In the case of the anisotropic XY antiferromagnet,
the transition region between the antiferromagnetic and spin-flop
phases is found to be dominated by degenerate bidirectional
fluctuations. The phase diagram is observed to resemble closely
that of the XXZ antiferromagnet without single-ion anisotropy. 相似文献