Entanglement Teleportation Via a Two-qubit Heisenberg Chain under a Nonuniform Magnetic Field

By introducing the nonuniform magnetic field, we investigate the entanglement teleportation via two-qubit Heisenberg chain. We show that for ferromagnetic chain, the opposite direction magnetic field on the two-qubit chain can excite the teleported entanglement C _out, while the uniform magnetic field can not do it. The effect of the uniform magnetic field B and the nonuniform magnetic field b on the threshold temperature T _c is also plotted. Our study on the average fidelity of this quantum channel system shows that the magnetic field in opposite direction can result in the ideal average fidelity no matter whether the chain is ferromagnetic or antiferromagnetic.     

Microwave specific loss power of magnetic fluids subjected to a static magnetic field

This paper reports on the frequency dependence of the magnetic and electric power dissipation in a magnetic fluid sample, in the microwave frequency range (0.5 to 8GHz), at various values of the static magnetic field (0 to 167.8kA/m). The computation of the power dissipation relies on the experimental values measured for the complex dielectric permittivity, ɛ = ɛ′ - iɛ″, and the complex magnetic permeability, μ = μ′ - iμ″, over the same frequency range. The results show that the magnetic power dissipation is much larger than the electric one for the investigated sample. At a specific frequency, f (Hz) , the power dissipation, p, depends on the external magnetic field, and exhibits a maximum. The result obtained suggests the possibility of controlling the energy absorption in the microwave range by means of the application of an external magnetic field.     

垂直场下磁性薄膜中的铁磁共振现象

将铁磁共振频率看成外磁场的函数, 讨论了垂直场下磁性膜中的铁磁共振现象. 结果显示: 当外磁场平行于膜面, 并考虑磁膜具有垂直磁晶各向异性情形时, 其磁共振频率随外磁场的变化分为高频支和低频支两种情况, 具体的依赖关系取决于磁膜内磁晶的各向异性; 当外磁场垂直于膜面, 其磁共振频率随外磁场的关系仅存在一支, 一般地, 磁共振频率随外磁场的增加单调地非线性减小, 但当立方磁晶各向异性场H_k1 与单轴磁晶各向异性场H_a之比值介于2/3 < H_k1/H_a <1时, 其磁共振频率随外磁场的增加单调增加, 这与相关的实验结果一致. 研究结果表明: 磁薄膜中有无垂直于膜面的磁各向异性可以通过其磁共振谱的测量进行辨析.     

Magnetism of fcc/fcc, hcp/hcp twin and fcc/hcp twin-like boundaries in cobalt

The magnetic moments of the fcc/fcc, hcp/hcp twin and fcc/hcp twin-like boundaries in cobalt were investigated by first-principles calculations based on density functional theory. The magnetic moments in fcc/fcc were larger than those of the bulk fcc, while the variations in the magnetic moment were complicated in hcp/hcp and fcc/hcp. The magnetovolume effect on the magnetic moment at the twin(-like) boundaries was investigated in terms of the local average atomic distance and the average deviation from equilibrium; however, the complicated variations in the magnetic moment could not be explained from the magnetovolume effect. Next, the narrowing (or broadening) of the partial density of states (PDOS) width of 3d orbitals, the number of occupied states for the spin-down channel, and the PDOS around the Fermi level were investigated. The entire variation in the magnetic moment at the twin(-like) boundaries could be understood in terms of these factors. Charge transfer occurred in hcp/hcp. In this case, the contributions of 4s and 4p electrons to the variation in the magnetic moment were relatively large.     

Interaction between magnetic agglomerates and an extended free radicals network studied by magnetic resonance

Solids containing an extended network of free radicals have been prepared and studied by magnetic resonance techniques in the 4–290 K temperature range. One solid contained additionally a small amount of magnetic γ-Fe₂O₃ in the form of nanoparticle agglomerates. The solid without agglomerates displayed only a narrow, single resonance line centered at g _eff = 2.0043. The magnetic resonance measurements of the solid with γ-Fe₂O₃ agglomerates gave a spectrum composed of two lines attributed to two different magnetic centers: a narrow line due to free radicals and a broad line arising from magnetic iron oxide agglomerates. In the high temperature range the integrated intensities of both lines decreased with decreasing temperature. The resonance field of the broad line shifted to lower magnetic fields upon lowering the temperature with the gradient ΔH _r /ΔT = 2.3 G/K, while the narrow line shifted towards higher magnetic fields. The linewidth of the broader line increased with decreasing temperature while for the narrow lines in both samples this change was small. The magnetic iron oxide clusters produce a magnetic field which acts on the free radicals network and its strength depends essentially on the concentration of clusters. The reorientation process in the free radicals network is more intense in the sample without magnetic clusters.     

Magnetic moment of an electron gas on the surface of constant negative curvature

The magnetic moment of an electron gas on the surface of constant negative curvature is investigated. It is shown that the surface curvature leads to the appearance of the region of the monotonic dependence M(B) at low magnetic fields. At high magnetic fields, the dependence of the magnetic moment on a magnetic field is the oscillating one. The effect of the surface curvature is to increase the region of the monotonic dependence of the magnetic moment and to break the periodicity of oscillations of the magnetic moment as a function of an inverse magnetic field.Received: 17 September 2003, Published online: 8 December 2003PACS: 73.20.At Surface states, band structure, electron density of states - 75.75. + a Magnetic properties of nanostructures     

Magnetic fields in 2D and 3D sphere

In this note we study the Landau–Hall problem in the 2D and 3D unit sphere, that is, the motion of a charged particle in the presence of a static magnetic field. The magnetic flow is completely determined for any Riemannian surface of constant Gauss curvature, in particular, the unit 2D sphere. For the 3D case we consider Killing magnetic fields on the unit sphere, and we show that the magnetic flowlines are helices with the given Killing vector field as its axis.     

Analysis of a penny-shaped crack in a magneto-electro-elastic medium

The solution for an ellipsoidal cavity in an infinite transversely isotropic magneto-electro-elastic medium under remotely applied axisymmetric, combined mechanical–electric–magnetic loading is derived. The exact solution for a penny-shaped crack is obtained by letting the minor axis of the ellipsoidal cavity approach zero. The results demonstrate that the stress intensity factor depends only on the applied mechanical loading, but the electric displacement intensity factor and the magnetic induction intensity factor depend on the applied combined loading, as well as the two ratios of β/α and γ/α. Parameter α is the ratio of the minor axis to the major axis of the ellipsoidal cavity, β is the ratio of the dielectric constant of the material in the cavity to the effective dielectric constant of the magneto-electro-elastic medium, and γ is the ratio of the magnetic permeability of the material in the cavity to the effective magnetic permeability of the magneto-electro-elastic medium. The two ratios characterize the permeability of the crack to electric and magnetic fields. Several limiting cases for β/α and γ/α are studied. A self-consistent method is adopted to determine the real crack opening α under the combined mechanical–electric–magnetic loading. The stress, electric displacement and magnetic induction intensity factors of a penny-shaped crack in BaTiO₃–CoFe₂O₄ composites are calculated for different volume fractions and different applied combined loadings.     

Logical XOR gate response in a quantum interferometer: A spin dependent transport

We examine spin dependent transport in a quantum interferometer composed of magnetic atomic sites based on transfer matrix formalism. The interferometer, threaded by a magnetic flux ϕ, is symmetrically attached to two semi-infinite one-dimensional (1D) non-magnetic electrodes, namely, source and drain. A simple tight-binding model is used to describe the bridge system, and, here we address numerically the conductance-energy and current-voltage characteristics as functions of the interferometer-to-electrode coupling strength, magnetic flux and the orientation of local the magnetic moments associated with each atomic site. Quite interestingly it is observed that, for ϕ = ϕ ₀/2 (ϕ ₀ = ch/e, the elementary flux-quantum) a logical XOR gate like response is observed, depending on the orientation of the local magnetic moments associated with the magnetic atoms in the upper and lower arms of the interferometer, and it can be changed by an externally applied gate magnetic field. This aspect may be utilized in designing a spin based electronic logic gate.     

A study on effect of current density on magnetic lenses

Attention has been concentrated on the effect of the current density on magnetic objective lens design. The optical properties of various objective lens types have been investigated in terms of current density σ. Arrangement of energizing coil on symmetric magnetic electron lenses also, has been examined. Favorable current density σ regions are estimated for the iron polepiece and iron free magnetic lenses.     

Effect of strong magnetic field on chemical potential and electron capture in magnetar

The chemical potential of electrons in a strong magnetic field is investigated. It is shown that the magnetic field has only a slight effect on electron chemical potential when B 〈 10^11 T, but electron chemical potential will decrease greatly when B 〉 10^11 T. The effects of a strong magnetic field on electron capture rates for ^60Fe are discussed, and the result shows that the electron capture sharply decreases because of the strong magnetic field.     

Local Thermodynamical Stability of Fermion Lattice Systems

We study the magnetic moment of neutral atoms in large magnetic fields. Asymptotic formulas for the energy exist with high precision in different regions depending on how large the nuclear charge Z is compared to the magnetic field strength B. All these formulas take the splitting of the kinetic energy into Landau levels as the principal feature and then treat the electric potential as a perturbation. We prove that these approximate formulas predict correctly'(to highest order) the total magnetic moment of the atom. The proof of this fact relies on a 'virial theorem' for Coulomb systems in a constant magnetic field.     

Investigation of in vitro efficiency of magnetic nanoparticle-conjugated <Superscript>125</Superscript>I-uracil glucuronides in adenocarcinoma cells

Modification of the magnetic properties of a drug can be used to direct the drug to the desired site, enhancing its therapeutic effectiveness and reducing side effects. In this study, surface-modified magnetic nanoparticles were immobilized with uracil glucuronide derivatives and then labeled with I-125. The morphology, structure, and composition of the magnetic particles were examined by TEM, SEM, VSM, and XRD. The particles sizes were about 50 nm. The labeling yield was 93.8% for uracil-O-glucuronide-immobilized magnetic particles and 95.0% for uracil-N-glucuronide-immobilized magnetic particles. The cell incorporation rates of N- and O-glucuronides were higher than those of uracil. The incorporation rates of uracil-, O-glucuronide-, and N-glucuronide-conjugated magnetic particles were all high. The cell incorporation rates of ligand-conjugated magnetic particles increased under a magnetic field.     

Collective Dust‐Dust Attraction in Strong Magnetic Field

It is shown that the collective dust‐dust attraction is enhanced by strong magnetic fields larger then the critical magnetic field determined be the condition that the Lorentz force acting on ions is larger than the friction of ions on dust grains related with the dust drag. It is demonstrated that with an increase of the magnetic field the deepness of the attraction potential well is increased in all directions to the magnetic field, that the distance of the minimum of the potential well along the magnetic filed (in both directions) is changed only slightly while the distance of the minimum of the attraction potential well is substantially decreased for directions perpendicular to the magnetic field. This means that the structures formed by attraction forces such as plasma crystals will be compressed perpendicular to the magnetic field (inter‐dust distance becomes smaller) and that the melting transition temperature should increased with an increase of the strength of the magnetic field. Numerical results are presented for dependence of the attraction potential well on the ratio of the strength of the magnetic field to the critical magnetic field strength, on the parameter P = n_dZ_d/n_i (n_d and n_i being the dust and ion densities respectively) and on the temperature ratio τ = T_i/T_e (T_e and T_i being the electron and ion temperatures respectively). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of magnetic quantization on the effective mass in semiconductor superlattices

An attempt is made to study the effect of a quantizing magnetic field on the effective electron mass in a semiconductor superlattice at low temperatures. It is found on the basis of the tight-binding approximation, taking GaAs-Ga_1–x Al _x As an example, that the effective mass at the Fermi level depends on the magnetic quantum number due to the cosine dependence of the wave-vector in the superlattice direction. The mass also exhibits oscillatory features in the presence of magnetic quantization because of its dependence on Fermi energy which oscillates with changing magnetic field.     

Investigation of the magnetic properties and magnetic structure parameters of nanocrystalline Fe<Subscript>79</Subscript>Zr<Subscript>10</Subscript>N<Subscript>11</Subscript> films

The magnetic properties (magnetization curve, ferromagnetic resonance spectrum) of nanocrystalline Fe₇₉Zr₁₀N₁₁ films obtained by RF magnetron sputtering with subsequent annealing were studied experimentally, along with the fundamental magnetic constants of these films (saturation magnetization M _S, local magnetic anisotropy energy K, and the exchange coupling constant A). The magnetic properties are discussed within the random magnetic model, which determines the correlation of the magnetic properties with the fundamental magnetic constants and nanostructure parameters (grain size, magnetic anisotropy, and correlation radius R _C). The exchange correlation length 2R _L for the film magnetic microstructure was determined by correlation magnetometry.     

Multilayer transition in a spin-1 Blume–Capel model with RKKY interaction and quantum transverse anisotropy

Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume--Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multilayer magnetic order--disorder transition temperature depends strongly on the value of the transverse anisotropy. The multilayer transition temperature decreases when increasing the transverse anisotropy. Furthermore, there exists a critical quantum transverse anisotropy Δ_xL beyond which the separate transitions occur in the two magnetic layers. The critical transverse anisotropy Δ_xL decreases (increases) on increasing the non-magnetic spacer of thickness M (on increasing the crystal field), and Δ_xL undergoes oscillations as a function of the Fermi level.     

Influence of magnetic fields on taylor vortex formation in magnetic fluids

The flow of a magnetic fluid placed inside a small gap between concentric rotating cylinders is investigated for axial, radial and azimuthal magnetic fields. An equation of motion is derived phenomenologically to describe the hydrodynamics of magnetic fluids. Studied are the changes in the critical Taylor numberT _c and wave numberT _c which characterize the instability of primary circular Couette flow towards Taylor vortices. It is found that all above magnetic fields have a stabilizing effect on circular Couette flow and thatT _c increases or decreases, depending on the direction of the magnetic field. Besides this, the influence of the magnetic fields on the correlation length ₀, the wave number of maximal growthk _m and the linear growth rate amplitude ₀ is determined.     

Quasistatic magnetic fields generated by a nonrelativistic intense laser pulse in uniform underdense plasma

Quasistatic magnetic fields generated by nonrelativistic intense linearly polarized (LP) and circularly polarized (CP) laser pulses in an initially uniform underdense plasma in the collision-dominated limit are investigated analytically. Using a selfconsistent analytical model, we perform a detailed derivation of quasistatic magnetic fields in the laser pulse envelope in the collision-dominated limit to obtain exact analytical expressions for magnetic fields and discuss the dependence of magnetic fields on laser and plasma parameters. Equations for quasistatic magnetic fields including both axial component B_z and the azimuthal one B_θ are derived simultaneously from such a selfconsistent model. The dependence of quasistatic magnetic field on incident laser intensity, transverse focused radius of laser pulse, electron density and electron temperature is discussed.     

Effects of the Mn/Co ratio on the magnetic transition and magnetocaloric properties of Mn1+xCo1-xGe alloys

We have investigated the magnetic transition and magnetocaloric effects of Mn 1+x Co 1 x Ge alloys by tuning the ratio of Mn/Co.With increasing Mn content,a series of first-order magnetostructural transitions from ferromagnetic to paramagnetic states with large changes of magnetization are observed at room temperature.Further increasing the content of Mn (x=0.11) gives rise to a single second-order magnetic transition.Interestingly,large low-field magnetic entropy changes with almost zero magnetic hysteresis are observed in these alloys.The effects of Mn/Co ratio on magnetic transition and magnetocaloric effects are discussed in this paper.