共查询到20条相似文献,搜索用时 15 毫秒
1.
Erhan Albayrak 《Physics letters. A》2018,382(13):880-886
The effect of single-ion anisotropy on the thermal properties of the ternary-alloy in the form of is investigated on the Bethe lattice (BL) in terms of exact recursion relations. The simulation on the BL consists of placing A atoms (spin-1/2) on the odd shells and randomly placing B (spin-3/2) or C (spin-5/2) atoms with concentrations p and , respectively, on the even shells. The phase diagrams are calculated in possible planes spanned by the system parameters: temperature, single-ion anisotropy, concentration and ratio of the bilinear interaction parameters for corresponding to the honeycomb lattice. It is found that the crystal field drives the system to the lowest possible state therefore reducing the temperatures of the critical lines in agreement with the literature. 相似文献
2.
We study the ground-state and thermal entanglement in the mixed-spin (S,s)=(1,1/2) Heisenberg chain with single-ion anisotropy D using exact diagonalization of small clusters. In this system, a quantum phase transition is revealed to occur at the value D=0, which is the bifurcation point for the global ground state; that is, when the single-ion anisotropy energy is positive, the ground state is unique, whereas when it is negative, the ground state becomes doubly degenerate and the system has the ferrimagnetic long-range order. Using the negativity as a measure of entanglement, we find that a pronounced dip in this quantity, taking place just at the bifurcation point, serves to signal the quantum phase transition. Moreover, we show that the single-ion anisotropy helps to improve the characteristic temperatures above which the quantum behavior disappears. 相似文献
3.
We solve the spin-1 quantum Ising model with single-ion anisotropy by mapping it onto a series of segmented spin-1/2 transverse Ising chains, separated by the S(z)=0 states called holes. A recursion formula is derived for the partition function to simplify the summation of hole configurations. This allows the thermodynamic quantities of this model to be rigorously determined in the thermodynamic limit. The low temperature behavior is governed by the interplay between the hole excitations and the fermionic excitations within each spin-1/2 Ising segment. The quantum critical fluctuations around the Ising critical point of the transverse Ising model are strongly suppressed by the hole excitations. 相似文献
4.
5.
6.
Specific features of spin ordering in an Ising antiferromagnet with single-ion easy-plane anisotropy
A thermodynamic analysis of spin ordering in an Ising antiferromagnet with single-ion easy-plane anisotropy is carried out. The solutions of the equations of state are analyzed, and the phase diagram is constructed. It is shown that an increase in the single-ion anisotropy constant as a result of increasing competition between single-ion anisotropy and exchange interaction brings about a crossover from the continuous phase transition to the abrupt phase transition. This is initiated by a change in the ion state populations due to single-ion anisotropy and by the freezing of ionic states with a nonzero spin projection. An increase in the single-ion anisotropy also leads to a crossover of the phase transformation between the paramagnetic and antiferromagnetic states from the order-disorder to order-order type. 相似文献
7.
The dimerized spin-1 Ising chain with both longitude and transverse single-ion anisotropies Dz and Dx is solved exactly by means of a mapping to the spin- Ising chain with the alternating transverse fields and the Jordan-Wigner transformation. The analytical expressions of the quasi-particles’ spectra Λk, the minimal energy gap Δ0 for exciting a fermion quasi-particle, the minimal energy gap Δh for exciting a hole, and the ground-state energy Eg are obtained. The phase diagram of the ground state is also given. The results show that the system exhibits a series of quantum phase transitions depending on the dimerization strength of the crystal fields, while the quantum critical points are determined exactly. 相似文献
8.
《Journal of magnetism and magnetic materials》1989,79(3):L271-L275
Surface magnetic properties of a semi-infinite ferrimagnetic mixed Ising alloy with a random surface single-ion anisotropy are investigated. We find a number of characteristic phenomena for the surface magnetism. In particular, the appearence of a compensation point only on the surface may be an important phenomenon for technological applications. 相似文献
9.
In this work we present a detailed numerical investigation on the magnetic domain formation and magnetization reversal mechanism in sub-millimeter amorphous wires with negative magnetostriction by means of micromagnetic calculations. The formation of circular magnetic domains surrounding a multidomain axially oriented central nucleus was observed for the micromagnetic model representing the amorphous wire. The magnetization reversal explained by micromagnetic computations for the M-H curve is described in terms of a combined nucleation-propagation−rotational mechanism after the saturated state. Results are interpreted in terms of the effective magnetic anisotropy. 相似文献
10.
Z. Liu R. BrandtO. Hellwig S. FlorezT. Thomson B. TerrisH. Schmidt 《Journal of magnetism and magnetic materials》2011,323(12):1623-1626
We present the measurements of the picosecond magnetization dynamics of Co/Pd multilayer films. The dynamic magnetization properties of sputtered multilayer films were analyzed as a function of Co layer thicknesses and applied bias field. Both the eigenfrequencies of the magnetization precession in the multilayers and the associated Gilbert damping exhibit extreme sensitivity to the magnetic layer thickness on an atomic monolayer scale. The eigenfrequency increases more than threefold when the Co thickness decreases from 7.5 to 2.8 Å, mainly due to the changes in effective saturation magnetization and perpendicular anisotropy constant. A concomitant 2.6-fold increase in the damping of the oscillations is observed and attributed to stronger interface dissipation in thinner Co layers. In addition, we introduce a quasi-1D micromagnetic model in which the multilayer stack is described as a one-dimensional chain of macrospins that represent each Co layer. This model yields excellent agreement with the observed resonance frequencies without any free parameters, while being much simpler and faster than full 3D micromagnetic modeling. 相似文献
11.
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
12.
Precessional switching of magnetization in CoPt and FePt nanofilms is investigated by solving the Landau–Lifshitz–Gilbert (LLG) equation analytically and numerically. Switching in these films occurs only above a critical value of the magnetic field, and it further depends on the magnetocrystalline anisotropy and saturation magnetization of the film. The presence of magnetic surface anisotropy in these films reduces the switching time significantly. Also, the switching time in the case of Pt-alloys of Co and Fe is low compared to that in the case of pure Co and Fe films. 相似文献
13.
14.
We present a detailed study of the magnetization reversal in perpendicularly magnetized (Pt/Co)3 multilayers with different values of the platinum interlayer thickness tPt. To study the magnetization reversal in our samples we combined measurements of relaxation curves with the direct visualization of domain structures. Magnetization reversal was dominated by domain wall propagation for tPt=1 nm and by domain nucleation for tPt=0.2 nm, while a mixed process was observed for tPt=0.8 nm. We interpret our results within the framework of a model of thermally activated reversal where a distribution of activation energy barriers is taken into account. The reversal process was correlated with the energy barrier distribution. 相似文献
15.
Entanglement spectrum and quantum phase transitions (QPTs) in S = 1 bond-alternative antiferromagnetic Heisenberg chain with single-ion anisotropy and magnetic field are investigated by the infinite time-evolving block decimation (iTEBD) method. The combined effects of the single-ion anisotropy and magnetic field have been discussed, and a rich ground-state phase diagram is obtained. We find that the single-ion anisotropy is advantageous to the stability of the 1/2 magnetization plateau. Both entanglement entropy and entanglement spectrum, as two model-independent measures, are capable of describing all the QPTs. Especially, doubly degenerate entanglement spectrum on even bond is observed in the 1/2 plateau phase. Besides constant spontaneous magnetization, three magnetization plateaus (M z = 0, 1/2, and 1) are found to have constant entanglement entropy, entanglement spectrum, and nearest-neighbor correlation. In addition, all the QPTs in such a model have been determined to belong to the second-order category. 相似文献
16.
17.
Yin-Zhong Wu 《Optics Communications》2010,283(7):1569-1574
With the introduction of Dzyaloshinskii-Moriya (DM) interaction, dynamics of the remote entanglement in one-dimensional Ising chains is investigated. It is found that the DM interaction can excite the remote entanglement from an initial Néel state. For a given strength of DM interaction, the concurrence between the end spins oscillates and decreases simultaneously with the increase of the chain’s length, and drops to zero at a critical length. For the chains with two and three spins, it is very interesting that the dynamics of the staggered magnetization (or the chiral parameter) can be used to qualitatively estimate the evolution of the remote concurrence between the end spins. At last, we discuss the generation of W state from the Ising chain with DM interactions, and it is obtained that W state can only be prepared in the three-qubit and four-qubit chains with a specific strength of DM interaction. 相似文献
18.
Effects of size and surface anisotropy on thermal magnetization and
hysteresis in the magnetic clusters 总被引:3,自引:0,他引:3
Z. Huang Z. Chen S. Li Q. Feng F. Zhang Y. Du 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(1):65-73
Based on Monte Carlo simulation, the spin configurations, thermal
magnetization and hysteresis loops of the clusters coated by the surface
shell with radial anisotropy are studied. Interestingly, a new multidomain
containing a few of subdomains whose easy directions are along those of the
configurational anisotropy, a magnetization curve in steps and a first order
phase transition from the single domain to the multidomain in the thermal
and field magnetization processes, are found, which is as a result of the
interplay of the configurational anisotropy, the size effect, the surface
anisotropy, the applied field and the thermal fluctuation. In this first
order transition, we find a critical temperature, a critical surface
anisotropy and a critical size. The simulated temperature dependence of the
coercivity of the cluster with the surface anisotropy can be fitted by Hc
(T)=Hc (0)(1-CαTα) with low value of α, which
explains well the experimental results of the nanoparticles. Moreover, it is
found that the hysteresis loops and coercivity are strongly affected by the
cluster size and the thickness of the surface layer. 相似文献
19.
Using the method of the Jordan--Wigner transformation for solving
different spin--spin correlation functions, we have investigated the
generation of next-nearest-neighbouring entanglement in a
one-dimensional quantum Ising spin chain with the Gaussian
distribution impurities of exchange couplings and external magnetic
fields taken into account. The maximal value of entanglement
between the next-nearest-neighbouring qubits in the transverse Ising
model was analysed in detail by varying the effectively controlled
parameters such as interchange coupling, magnetic field and the
system impurity. For such systems, where both exchange couplings and
external magnetic field disorder appear, we show that it is possible
to achieve next-nearest-neighbouring entanglement better than the
previously discussed pure Ising spin chain case. We also show that
the Gaussian distribution impurity can induce
next-nearest-neighbouring entanglement, which can be used as a means
to characterize quantum phase transition. 相似文献