The magnetic field,force and inductance of the system consisting of a thin ellipsoidal coil and a ferromagnetic ellipsoid

The method of separation of variables has been applied to determine the magnetic field of the system consisting of a thin ellipsoidal coil and a ferromagnetic ellipsoid of revolution. The inductance and the force acting between the coil and the ellipsoid are also examined.     

均匀磁化永磁棒的磁场

本文综合运用分子电流观点及磁荷观点,系统地计算了沿轴向、横向及其它任意方向均匀磁化的有限长永磁棒在轴线上的磁场以及无限长永磁棒在全空间的磁场.     

The theory of ferromagnetic and spin-wave resonance in a thin film magnetized parallel to its own plane

The excitation of spin waves in a thin magnetic film magnetized parallel to its own plane is examined, commencing with a solution of the Landau-Lifschitz equation with general boundary conditions. The effects on the excitation spectrum of finite damping, finite spin fixation on the film surface, and inhomogeneous distribution of the shf field over the film thickness are examined.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 105–111, December, 1971.     

分子束外延制备的垂直易磁化MnAl薄膜结构和磁性

系统地研究了利用分子束外延方法在GaAs(001) 衬底上外延生长的MnAl_x薄膜的结构和垂直易磁化特性随组分及生长温度的依赖关系. 磁性测试表明, 可在较大组分范围内 (0.4≤x≤1.2) 获得大矫顽力的垂直易磁化MnAl_x薄膜, 然而同步辐射X射线衍射和磁性测试发现当x≤0.6时MnAl薄膜出现较多的软磁相, 当x >0.9时, MnAl薄膜晶体质量和化学有序度逐渐降低, 组分为MnAl_0.9时制备的薄膜有最好的[001]取向. 随着生长温度的增加, MnAl_0.9薄膜的有序度、垂直磁各向异性常数、矫顽力和剩磁比均增加, 350℃时制备的MnAl_0.9薄膜化学有序度高达0.9, 其磁化强度、剩磁比、矫顽力和垂直磁各向异性常数分别为265emu/cm³、93.3%、8.3kOe (1 Oe=79.5775A/m)和7.74Merg/cm³ (1 erg=10^-7J). 不含贵金属及稀土元素、良好的垂直易磁化性质、 与半导体材料结构良好的兼容性以及磁性能随不同生长条件的可调控 性使得MnAl薄膜有潜力应用于多种自旋电子学器件. 关键词： 分子束外延 大矫顽力材料 磁各向异性     

线电流与楔形铁磁质所形成的磁场

利用复数坐标系z上的保角变换,计算长直线电流与无限大楔形铁磁质所形成的磁场,给出其磁矢势的分布,并利用数学软件MATLAB绘制出磁感线分布图.     

平面约束下金属铁磁条中平行抽运微波磁场的非稳定阈值研究

运用Landau-Lifshitz方程,边界处动态磁化强度由有效偶极边界条件约束,研究了无限长金属磁条中自旋波传播的特征,得到了该体系抽运微波磁场的阈值曲线以及色散曲线的解析式,揭示出自旋波激发谱与磁条宽度的具体关系.结果表明,平面约束下磁条的阈值曲线中出现了明显的扭结现象.并且随着磁条宽度的增加,其扭结数近似地呈指数形式增加,而最低扭结处两阈值的跳跃差值几乎呈反比形式变化. 关键词： Landau-Lifshitz方程 有效偶极边界条件 阈值曲线 色散曲线     

The parallel permittivity of magnetized toroidal plasmas with elliptic magnetic surfaces

The asymptotic solution of the Vlasov equation under the drift approximation, for an axially symmetric toroidal plasma configuration with an elliptic cross section of magnetic surfaces, is presented. The analytical expressions for the parallel component of the dielectric permittivity tensor are obtained. These expressions are used for theoretical analyses of the trapped and untrapped electron influence on the collisionless wave dissipation. The evaluated dielectric tensor components can be used for computer calculations of the radio frequency field structure and the collisionless dissipated power related to trapped and untrapped electrons in tokamak plasmas.This work was supported by the State University of Rio de Janeiro (UERJ), Rio de Janeiro Research Foundation (FAPERJ) and Brazilian National Council of Research (CNPq).     

线电流与条形铁磁质板所形成的磁场

利用已有的儒可夫斯基变换结论,通过圆柱镜像法,计算线电流与薄条形铁磁质板所形成的磁场,给出其磁矢势的分布和磁感线方程,并利用数学软件MATLAB绘制出磁感线图.     

Surface plasmon in a parallel magnetic field

Using a hydrodynamic model the dispersion relation for the surface plasmon is calculated in an external magnetic field parallel to the surface when the wave propagates perpendicular to the magnetic field. In the limit of zero wave vector, the results reduce to those of Chiu and Quinn who have used the dielectric constant in the local theory.     

Two-dimensional metal in a parallel magnetic field

We have investigated the effect of an in-plane parallel magnetic field (B(axially) on two high mobility metallic-like dilute two-dimensional hole gas systems in GaAs quantum wells. The experiments reveal that, while suppressing the magnitude of the low temperature resistance drop, B(axially) does not affect E(a), the characteristic energy scale of the metallic resistance drop. The field B(c) at which the metallic-like resistance drop vanishes is dependent on both the width of the quantum well and the orientation of B(axially). It is unexpected that E(a) is unaffected by B(axially) up to B(c) despite the fact that the Zeeman energy at B(c) is roughly equal to E(a).     

Thin ferromagnetic nanodisk in transverse magnetic field

The magnetization of a ferromagnetic nanodisk is studied using micromagnetic modeling. It is demonstrated that, under an external magnetic field applied perpendicular to the disk surface, magnetic phase transitions can occur between uniform states, between uniform and vortex states, and between vortex states with different directions of polarization. A simple variation model is proposed describing the observed magnetic states quantitatively.     

The spontaneous magnetization of a one-dimensional model of a ferromagnetic toroid in a magnetic field

The paper deals with the derivation of the dependence of the spontaneous magnetization on the temperature and the intensity of the magnetic field for a one-dimensional model of a ferromagnetic toroid. For a chain formed of N10H ^–1/2 particles this dependence has the form of a half-power law modified by exponential dependence on H/T for temperatures and intensities of the magnetic field for which H/T10.     

Local magnetic field at a positive muon in ferromagnetic gadolinium

The local magnetic field at a stopped positive muon has been measured in polycrystalline gadolinium as a function of temperature between 20 K and the Curie point. The measurements show that the muon occupies the octahedral interstitial site and demonstrate the sensitivity of the muon as a probe of the local magnetic structure.     

Wigner liquid conductivity in a parallel magnetic field

It is assumed that comparatively low-mobility objects (clusters of a small number of electrons) can appear in a two-dimensional strongly correlated electronic system (Wigner liquid) against the background of mobile Fermi-type carriers. These formations can get “pinned” to inhomogeneities and play the role of additional scatterers. Clusters of two and three electrons are discussed (for a short-range order in the arrangement of electrons, as in a triangular lattice). The number of these clusters depends on both temperature and the parallel magnetic field. This results in the temperature and field dependences of the resistance and magnetization of the system. According to a simple model, resistance increases and the metal-dielectric transition occurs as the parallel magnetic field grows stronger. The model predicts a nonlinear magnetic field dependence of magnetization.     

The magnetic hyperfine field at Hg impurities in ferromagnetic Gd

The magnetic hyperfine field at dilute Hg impurities in Gd has been investigated by the conversion electron (e ^–)--time differential perturbed angular correlation (TDPAC) technique. The radioactivities^197m Hg and¹⁹⁹Tl were implanted into Gd foils by means of an isotope separator. TDPAC measurements were performed with the 165 keV-L-conversion electron—134 keV--cascade of¹⁹⁷Hg at different temperatures and with the 334 keV--158 keV-K-conversion electron cascade of¹⁹⁹Hg at 200 K.The regular site occupation probabilities were found to be 15(3)% for an annealed^197m HgGd sample and 29(5)% in unannealed¹⁹⁹TlGd samples.From the magnetic hyperfine interaction frequencies measured for the regular sites at 200 K the magnetic hyperfine fields |H _hf(¹⁹⁷HgGd; 200 K)|=256(13) kG and |H _hf(¹⁹⁹HgGd; 200 K)|=267(7) kG were deduced.On leave from the University of Lisboa, Portugal     

Increase in temperature of a ferromagnetic substance in rf magnetic field

If one applies an rf magnetic field parallel to a strong static field, temperature of a ferromagnetic substance rises due to ferromagnetic resonance. This phenomenon finds immediate application in the field of hyperthermic oncology. In this work, we have found expression for the increase in temperature when a ferromagnetic material is placed under a static and a varying magnetic field of high frequency through spin wave approach. The numerical value of this increment of local temperature has been estimated for yttrium iron garnet (YIG). We also have examined the possibility of enhancing the temperature of a ferromagnetic material only by applying a strong static field.     

Optical absorption and magnetotransport in quantum wires in a perpendicular magnetic field

A periodic array of δ function potentials are used to simulate the potential barriers between quantum wires in the presence or absence of lattice site dislocation. The exact eigenenergies and eigenfunctions are found by employing a numerical diagonalization procedure. Based on these results, a self-consistent field theory is derived for the mid-infrared absorption coefficient of the system. The crossover from a cyclotron mode to two tunneling coupled modes and finally to edge and 1D lattice magnetoplasmon modes with increasing modulation strength is investigated. The magnetic field enhanced and suppressed electron tunneling, associated with the evolution to cyclotron modes at strong magnetic fields passing through the formation of tunneling coupled modes, is observed. The edge mode excitation energy oscillates as a function of the electron density. These oscillations correspond to a soft or hard potential wall for which the electron states are extended or localized, respectively. The displacement of the 1D lattice magnetoplasmon modes under strong modulation is found to be periodic and corresponds to the evolution from a complex unit cell which is composed of one narrow and one wide quantum wire to a simple unit cell containing only one quantum wire. The magnetoresistivities and the associated conductivities are also calculated for the lateral surface superlattice. At strong potential modulation there is a giant peak in the Hall conductivity and many peaks in its resistivity in the quantum regime. With strong modulation, the suppression of the transverse conductivity along with oscillations in its resistivity are obtained.