The magnetic field and force in a perpendicularly magnetized matrix consisting of parallel ordered ferromagnetic wires

A formula for the magnetic field arising in a periodically ordered array of ferromagnetic wires, whose magnetization is saturated in a perpendicularly applied field, is derived. Thereby it is assumed that the stray fields do not affect the magnetization of the wires. It is shown that for an arbitrary infinite lattice of wires the exact solution of the magnetostatic equations is given by the Weierstrass $\text{p}$-function and how this function can be used to approximate the field in a finite array of wires. In view of applications to HGMS an expression for the magnetic force acting on a small weakly magnetic particle in a ferromagnetic matrix is derived, which is well-suited for numerical calculations.     

椭球形线圈磁场均匀性的研究

用我们提出的数字图像法研究了载流椭球形线圈内部磁场的均匀性.利用Mathematica杰出的计算能力和数字绘图功能,绘制了疏绕旋转椭球形线圈磁场的三维分布图,给出了满足各种指定均匀度所对应的椭球区域,指出了现有文献研究圆柱形均匀区的不合理性.本文为电磁场均匀性研究提供了一种方便可靠的方法.     

Electron states and light absorption in a thin ellipsoidal quantum lens in the presence of a strong magnetic field

Within the framework of adiabatic approximation the energy levels and direct interband light absorption in a thin ellipsoidal quantum lens in the presence of a magnetic field are studied. Analytical expressions for the particle energy spectrum and for the absorption threshold frequencies in the regime of strong size quantization for the cases of ellipsoidal and spherical cross-section segments are obtained. Selection rules for quantum transitions are revealed.     

Conductivity in a system of ferromagnetic nanoclusters: the influence of a magnetic field

A theory of the conductivity of insulator + metal nanoclusters composites was developed. The rate constant for tunnel electron transfer between nanoclusters was obtained. Three current passage regimes are possible, regimes of weak, strong, and superstrong electric fields. At weak fields, the distribution of electrons produced in the ionization of neutral clusters is almost equilibrium. Conductivity under these conditions was calculated. A strong magnetic field dependence of the resistance of ferromagnetic clusters is possible. An exact equation for the magnetic field and temperature dependences of resistance was obtained.     

应用载流线圈的费曼模型再谈非均匀磁场对载流线圈的作用

应用载流线圈的费曼模型推导了任意载流线圈在非均匀磁场中所受作用力及力矩的公式。     

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.     

Penetration of a magnetic field into a thin unclosed ellipsoidal sheath in the presence of a thick-walled conducting spherical sheath

The solution of the problem of magnetic field penetration into a conducting unclosed ellipsoidal sheath in the presence of a conducting thick-walled spherical sheath is reduced to the solution of the integral Fredholm equation of the second kind. The effect of the apex angle of the unclosed ellipsoidal sheath, geometric parameters of the screens, and electrophysical properties of the spherical sheath material on the field attenuation coefficient inside the ellipsoidal sheath is studied numerically.     

均匀磁化介质椭球的退磁因子及退磁场

在椭球坐标系中求解了均匀椭球磁介质在匀强磁场中的磁化问题,得到了空间磁标势、磁场、介质中退磁场和退磁因子的表达式,研究了椭球形状与退磁因子的关系,分析了介质磁化率对退磁场方向的影响.结论为:椭球磁介质内的退磁场是匀强磁场;退磁因子的大小与椭球形状有关,与椭球大小无关,沿椭球长轴方向的退磁因子较小;一般而言退磁场方向与外磁场方向既不相同也不相反.铁磁质椭球内的退磁场几乎与外磁场反向.     

Influence of an electric field on the ferromagnetic resonance in a plane-layered magnetic system

The influence of an electric field on the ferromagnetic resonance (FMR) in a multilayer magnetic system consisting of two magnetic layers separated by a thin nonmagnetic interlayer has been investigated. It has been shown that, upon the excitation of magnetization oscillations by a microwave magnetic field, the eigenfrequencies of the ferromagnetic resonance depend on the stationary electric field applied in the plane of the layers. It has also been demonstrated that, in this system, high-frequency magnetization oscillations can be excited by an electric microwave field. The results of the investigation of the polarization properties of the excitation mechanism indicate that this effect can be observed experimentally.     

Effect of a strong magnetic field on the chemical equilibrium of the ferromagnetic hydride-hydrogen system

The hydrogen pressure of the ferromagnetic SmCo₅H_x and LaCo₅H_x systems has been measured as a function of magnetic fields up to 7 T. Magnetic fields cause considerable rises in the pressure. The logarithmic pressure change, ln(P_H/P₀), in the β + γ region of LaCo₅H_x is 0.095 in 7 T at room temperature.     

Optimization of a data storage system based on the array of ferromagnetic particles and magnetic force microscope

Optimal parameters for a data storage system based on ferromagnetic particles and magnetic force microscope (MFM) are calculated. The conditions necessary for data recording, storing, and reading are analyzed in the frame of a simple model of a spherical MFM probe and an array of spherical single-domain particles. The ultimate data densities in such a system are estimated.     

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.     

Properties of Josephson junctions in the inhomogeneous magnetic field of a system of ferromagnetic particles

The effect of a system of ferromagnetic particles on the field-dependent critical current of a Josephson junction is experimentally studied for junctions of different geometries. For edge junctions, the effect of commensurability between the periodic magnetic field of the particles and the Josephson vortex lattice is observed. The effect manifests itself in additional maxima of the field-dependent critical current. For overlap junctions, giant (greater than sixfold) variations of the maximum critical current are observed depending on the magnetic state of the particles. The changes in the “Fraunhofer” pattern of the overlaped Josephson junctions are attributed to the formation of Abrikosov vortices due to the effect of uniformly magnetized particles. The effects revealed in the experiments can be used to analyze the inhomogeneous magnetic field of a system of submicron particles and to control the transport properties of Josephson junctions.     

Properties of Josephson junctions in the inhomogeneous magnetic field of a system of ferromagnetic particles

The effect of an array of ferromagnetic nanoparticles on the field-dependent critical current of the short overlap Josephson junction is experimentally studied. Large reversible variations of the maximum critical current are observed depending on the magnetic state of the particles. The pronounced commensurability effects are detected which are proved by the additional peaks of magnetic field induced diffraction pattern.     

Effect of a magnetic field on the microhardness of ferromagnetic fields

The microhardness of ferromagnets is studied as a function of an external magnetic field. The maximum values of the relative change in microhardness during measurement without a field and in a magnetic saturation field for low-carbon iron, Kh16 steel, and the powder alloys Fe-TiC (ferroTiC) and PG-KhN80SR-4 are 20–34%. The effect of various processes of change in the magnetic structure on the measured microhardness of the ferromagnet is examined. A relation is established between the effect and the change in magnetic energy due to external stresses.Tula State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 30–33, September, 1994.     

Conductivity of composites containing ferromagnetic nanoparticles: The role of a magnetic field

A theory of conductivity is developed for metal-containing nanocomposites. An expression is obtained for the tunneling rate of an electron between nanoparticles. Three regimes of current flow are possible: the cases of weak, strong, and superstrong electric fields. In the weak-field regime, the electrons generated as a result of ionization of neutral nanoparticles are characterized by a nearly equilibrium distribution. The conductivity in this regime is calculated with the use of this nearly equilibrium distribution of electrons and the relationship between the spacing of neighboring particles and their radii. An expression is obtained for the electric conductivity as a function of temperature and a magnetic field (for ferromagnets) with regard to the distribution of nanoparticles with respect to radius and their volume density.     

Explicit solutions to phenomenological models of magnetization reversal of thin ferromagnetic films in the presence of a sawtooth magnetic field

Explicit solutions are derived for several phenomenological models of magnetization reversal in thin ferromagnetic films driven by a sawtooth magnetic field. For a domain wall velocity that is linear in the magnetic field, it is found that the dynamic coercive field follows a square-root power-law in the slope of the magnetic field, shifted by the depinning field. For a more general domain wall velocity different power-law exponents are found, yet the overall form for the scaling of the area of the hysteresis loop remains a power-law shifted by the depinning field. This shifted power-law could be interpreted to be a crossover between adiabatic and dynamic regimes.     

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.     

利用智能手机磁传感器测量亥姆霍兹线圈磁场

通过预实验确定智能手机磁传感器的位置后,用其测量亥姆霍兹线圈轴线的磁场分布,验证毕奥-萨伐尔定律及磁场的叠加原理,提供一种较为精确而简便的测量磁场的新方法.     

Effect of electric field on the magnetic characteristics of a ferromagnetic nanosemiconductor

A theory is developed to describe the effect of an electric field on the magnetization of a thin ferromagnetic semiconductor plate. It is shown that the magnetic moment density is nonuniform under these conditions and that the total magnetic moment and its density depend on the electric field and the temperature. An electric field is found to increase the Curie temperature, and an inflection point is detected in the temperature dependence of the derivative of the total magnetic moment with respect to temperature.