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1.
半经典闭合轨道理论已经成功地计算了在外加磁场和平行电磁场中的里德堡原子的回归谱.但对于垂直电磁场中的里德堡原子,理论和计算都变得更为复杂.本文把闭合轨道理论推广到三维情况,采用 B.Hüpper的模型势计算了ε=-0.03,主量子数n≈ 40,m=0下He原子在垂直电磁场中的光吸收谱和回归谱,并和H原子在垂直电磁场中的回归谱作比较,突出了实散射的贡献.计算中应用了离子实散射的分区自洽迭代方法,并考虑到轨道的多次重复和离子实的多次散射效应.这是对闭合轨道理论的验证和进一步推广. 相似文献
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《Physics Reports》1988,169(6):329-384
In this review we discuss the application of MHD theory to plasma in two contexts: the solar atmosphere and magnetically confined fusion experiments. The MHD equations are set up, and their relevance to the two systems discussed. It is shown that in both cases the resistivity is small, and the magnetic field is strong, so that similar physical behaviour should be expected. Three areas of research with relevance to both systems are described, the basic theory and some recent developments being outlined. These are magnetostatic equilibrium, linear stability theory and wave propagation, and relaxation of magnetic fields and helicity conservation. 相似文献
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D. Muraca F.H. Sánchez F.D. Saccone 《Journal of magnetism and magnetic materials》2010,322(6):705-708
Advances in theory that explain the magnetic behavior as function of temperature for two phase nanocrystalline soft magnetic materials are presented. The theory developed is based on the well known random anisotropy model, which includes the crystalline exchange stiffness and anisotropy energies in both amorphous and crystalline phases. The phenomenological behavior of the coercivity was obtained in the temperature range between the amorphous phase Curie temperature and the crystalline phase one. 相似文献
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In multiferroic ferroelectromagnets, microscopic coupling interaction
between the ferroelectric and magnetic order results in the macroscopic
correlation between the dielectric and magnetic properties, which is defined
as magnetodielectric effect. If we classify multiferroic ferroelectromagnets
as two kinds: ferroelectric-ferromagnets and ferroelectric-antiferromagnets,
we find the magnetodielectric behavior of these two kinds of
ferroeletromagnets show obvious difference. We analyze the origin of the
different magnetodielectric behavior and find that the fluctuation of the
spin-pair correlation plays a critical role. Soft-mode theory based on
DIFFOUR model and the mean-field theory are combined to deal with
multiferroic ferroelectromagnetic system. 相似文献
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Haskel D Lang JC Islam Z Cady A Srajer G van Veenendaal M Canfield PC 《Physical review letters》2005,95(21):217207
The magnetic moment reversal at each of the two inequivalent Nd sites in a single crystal of ferromagnetic Nd(2)Fe(14)B is probed by dichroic resonant diffraction of circularly polarized x rays. The results, supported by theory, show that the c-axis intrinsic magnetic stability of this superior permanent magnetic material arises predominantly at one of the Nd sites (g). The other site (f) undermines magnetic stability by favoring a magnetic moment orientation in the basal plane. 相似文献
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A self-consistent theory of dyons in Abelian and non-Abelian limits has been formulated in terms of an extra magnetic symmetry
and topological magnetic charge. It has been shown that the restricted gauge potential describes the fields of dyons in terms
of two regular (time-like) potentials only when recourse is made to the duality of topological (magnetic) and isocolour (electric)
charges. Choosing a suitable Lagrangian density for the system of dyons in non-Abelian gauge theory, the field equations,
energy-momentum tensor, Hamiltonian and momentum densities have also been derived and the conservation of the four-linear
momentum and the total angular momentum has been demonstrated. 相似文献
10.
Quantum spin transport through Aharonov--Bohm ring with a tangent magnetic field 总被引:1,自引:0,他引:1
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Quantum spin transport in a mesoscopic Aharonov--Bohm ring with two leads subject to a magnetic field with circular configuration is investigated by means of one-dimensional quantum waveguide theory.Within the framework of Landauer--B\"{u}ttiker formalism, the polarization direction of transmitted electrons can be controlled either by the AB magnetic flux or by the tangent magnetic field. In particular, the spin flips can be induced by hopping the AB magnetic flux or the tangent field. 相似文献
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The influence of magnetic field on the acoustic and magnetic properties of magnetic liquids is discussed. By fitting the curve of Taketomi's theory to the experimental data of the anisotropy of ultrasonic attenuation, the values of quantities describing the structure of magnetic liquids have been determined. Moreover, the dependence of magnetic susceptibility on frequency has been measured. It shows that two processes of magnetization, based on the mechanisms proposed by Brown and Neel, contribute to the magnetization of the magnetic liquid. 相似文献
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Axial buckling of current-carrying double-nanowire-systems immersed in a longitudinal magnetic field is aimed to be explored. Each nanowire is affected by the magnetic forces resulted from the externally exerted magnetic field plus the magnetic field resulted from the passage of electric current through the adjacent nanowire. To study the problem, these forces are appropriately evaluated in terms of transverse displacements. Subsequently, the governing equations of the nanosystem are constructed using Euler–Bernoulli beam theory in conjunction with the surface elasticity theory of Gurtin and Murdoch. Using a meshless technique and assumed mode method, the critical compressive buckling load of the nanosystem is determined. In a special case, the obtained results by these two numerical methods are successfully checked. The roles of the slenderness ratio, electric current, magnetic field strength, and interwire distance on the axial buckling load and stability behavior of the nanosystem are displayed and discussed in some detail. 相似文献
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Electron acceleration during magnetic islands coalescence and division process in a guide field reconnection
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The magnetic merging process related to pairwise magnetic islands coalescence is investigated by two-dimensional particle-in-cell simulations with a guide field.Owing to the force of attraction between parallel currents within the initial magnetic islands,the magnetic islands begin to approach each other and merge into one big island.We find that this newly formed island is unstable and can be divided into two small magnetic islands spontaneously.Lastly,these two small islands merge again.We follow the time evolution of this process,in which the contributions of three mechanisms of electron acceleration at different stages,including the Fermi,parallel electric field,and betatron mechanisms,are studied with the guide center theory. 相似文献
14.
Xiao Kong Jing He Yang Li Su-Peng Kou Ying Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(9):205
Spin-half paramagnetism induced by point detects was found in graphene recently,micromechanism of this magnetic response can be explained well by the intrinsic magneticimpurity theory. In this paper, we apply this theory to two types of single-walled carbonnanotubes (SWCNs) and calculate the properties of various magnetic interactions forcomparison. Interestingly, magnetic interactions have different behaviors in thesesystems. Following our calculation, within a short length, the interactions can besuppressed by ether size effect or a tiny band gap, and then exhibit exponentiallydecaying. However, in the absence of a band gap, the RKKY interaction could leave a tinytail at long range, which determines long range magnetic order. Further more, when a tinyband gap exist in the systems, the Heisenberg coupling is the dominate one due to theexpanded wavefunction. According to these result, vacancy states in different types ofSWCNs could form different magnetic order, bringing abundant candidates forapplication. 相似文献
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Buividovich PV Chernodub MN Kharzeev DE Kalaydzhyan T Luschevskaya EV Polikarpov MI 《Physical review letters》2010,105(13):132001
We study the correlator of two vector currents in quenched SU(2) lattice gauge theory with a chirally invariant lattice Dirac operator with a constant external magnetic field. It is found that in the confinement phase the correlator of the components of the current parallel to the magnetic field decays much slower than in the absence of a magnetic field, while for other components the correlation length slightly decreases. We apply the maximal entropy method to extract the corresponding spectral function. In the limit of zero frequency this spectral function yields the electric conductivity of quenched theory. We find that in the confinement phase the external magnetic field induces nonzero electric conductivity along the direction of the field, transforming the system from an insulator into an anisotropic conductor. In the deconfinement phase the conductivity does not exhibit any sizable dependence on the magnetic field. 相似文献
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Temperature magnetism of disordered iron–aluminum alloys in a model of two intra-atomic interactions
V. I. Grebennikov D. I. Radzivonchik 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(3):323-326
A system of band electrons with the two constants of intra-atomic exchange interaction simulates the different local environment of magnetic atoms in alloys. Temperature behavior of the magnetic characteristics of disordered Fe-Al alloys is investigated on the basis of an improved theory of dynamic fluctuations in electron spin density. The nature of the alloys’ different properties and the unusual temperature dependence of the magnetization and magnetic susceptibility is discussed. 相似文献
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Tsung-han LIN 《理论物理通讯》1986,6(4):291-300
We present a generalization of thermodynamic perturbation theory to the intermediate valence systems with two magnetic configurations. 相似文献
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R. T. Tagiyeva 《Pramana》2004,63(3):633-641
Localized magnetic polaritons are investigated in the systems consisting of two magnetic superlattices, coupled by a ferromagnetic
contact layer. The general dispersion relation for localized magnetic polaritons are derived in the framework of the electromagnetic
wave theory in the Voigt geometry by the ‘transfer’ matrix method. The numerical calculations were carried out for different
parameters of the superlattices and contact layer and then discussed. 相似文献
19.
F.C. Frank 《物理学进展》2013,62(1):91-109
The article attempts to review the present stage of the density functional theory for noncollinear magnetic states and its application to particular physical problems. The discussion starts with basic theorems of the theory and derivation of the Kohn-Sham equation for a noncollinear magnet. Special features of solving this equation are illustrated using the augmented-spherical-wave method generalized to the noncollinear magnetic structures as an example. Particular attention is devoted to the symmetry of the problem. It is shown that a traditional approach of the space group theory fails in the case of a noncollinear magnetic state. A generalized approach based on the notion of the spin space groups is presented which allows a consequent treatment of the symmetry properties of both nonrelativistic and relativistic problems. This approach allows the development of an exact procedure for a first-principles calculation of an incommensurate spiral structure and gives a sound basis for the calculation and physical interpretation of the noncollinear magnetic structures caused by the effects of relativity. Application of the theory to the first-principles determination of the complex noncollinear magnetic structures of various systems are discussed. Applications include the spiral structure of fcc Fe, the uncompensated magnetic structure in U3X4 and compensated magnetic structure in U2P2Sn, and two different types of weak ferromagnetism in Fe2O3 and Mn3Sn. It is shown how the calculation technique can be applied to studies of unenhanced and enhanced non-uniform magnetic susceptibilities as well as susceptibilities in fields noncollinear to the atomic moments. Illustrating results of the calculation of the susceptibility of various systems are presented. The last part of the review is devoted to applications of the theory of noncollinear magnetism to studies of temperature effects in the electronic properties of itinerant magnets. 相似文献
20.
We present a comprehensive simulation study of the Newtonian and quantum model of a Stern–Gerlach experiment with cold neutrons. By solving Newton’s equation of motion and the time-dependent Pauli equation for a wide range of uniform magnetic field strengths, we scrutinize the role of the latter for drawing the conclusion that the magnetic moment of the neutron is quantized. We then demonstrate that a marginal modification of the Newtonian model suffices to construct, without invoking any concept of quantum theory, an event-based subquantum model that eliminates the shortcomings of the classical model and yields results that are in qualitative agreement with experiment and quantum theory. In this event-by-event model, the intrinsic angular momentum can take any value on the sphere, yet, for a sufficiently strong uniform magnetic field, the particle beam splits in two, exactly as in experiment and in concert with quantum theory. 相似文献