The measurement of magneto-optical Kerr effect of ultrathin films in a pulsed magnetic field

A Kerr rotation measurement system in a pulsed magnetic field (up to 11 T) was built to study magnetic properties of several ultrathin films. Our result shows that the Kerr rotation angle increases with the increasing wavelength of the incident light, while the difference between the spectras of Fe and CoFeAl is attributed to plasma resonance. We also studied the dynamic properties of the magnetic films: while ferromagnetic materials (Fe, CoFeAl, MnAs and CoMnAl) show quasi-static behavior in the time-scale of a few 100 μs, diamagnetic material GaAs shows time-dependent hysteresis.     

Statistics of errors in a high-bit-rate optical communication link with reduction of the Kerr nonlinearity effect

Direct numerical modeling of propagation of optical pulses is performed to determine the “tails” of the probability density function of marks and spaces and the statistics of errors in an optical communication link on the basis of a standard single-mode fiber and a dispersion-compensation fiber with a reduced density of marks in the initial bit sequence. Simple analytical approximations for the tails of the probability density function are determined, which allows accurate estimation of the error probability in the link.     

A pulsed system for powering the magnetic coils of an ion diode with external magnetic insulation

A pulsed power system of magnetic coils of an ion diode with external magnetic insulation (IDM), which ensures operation of the diode in the frequency mode, is described. Demands are formulated for the IDM magnetic field in which the electronic cloud acting as a cathode in the diode is formed and for storage conditions of the negative charge in the magnetic field for neutralizing the ion beam in the ion-beam drift area. Basic relationships required for engineering calculations of the IDM coils and a pulsed power system in the frequency mode are given.     

超分辨近场结构光磁混合存储介质温度场模拟

为了进一步减小光磁混合存储记录位尺寸,建立了用于光磁混合存储记录介质的超分辨近场结构膜层模型、近场光场模型及温度场模型,采用有限元方法对超分辨近场结构光磁混合存储介质记录层的温度场进行了计算模拟。计算中采用的光磁混合记录介质膜层结构为C(2nm)/Sb(10nm)/SiN(10nm)/Co75Cr15Pt10(30nm). 当写入温度为550K时,随着入射激光功率的增加,光磁混合存储介质记录层温度场可写入区域面积增加。当激光功率从3.9mw增至6.9mw时,温度场可写入区域横向及纵向尺寸增加约1倍,记录密度减小至原记录密度的四分之一。     

Effect of pulsed magnetic field on the grain refinement and mechanical properties of 6063 aluminum alloy by direct chill casting

This paper presents different analyses by cooperation of multimobile micromanipulation systems (M⁴S) for robotic microassembly where assembly is performed in a grid pattern by dividing it into different zones. To cater this need, a new design of M⁴S for robotic assembly is proposed where different peg-in-hole assemblies are carried out. For attempting the different combinations by cooperation of M⁴S, a novel algorithm is developed which provides a solution for robotic microassembly in a more efficient and precise manner within less time. Experientially, it is proved that this novel design of M⁴S is capable of performing the different manipulation tasks of miniature parts. Different analyses prove its potentiality of robotic assembly in industrial applications.     

Ion source with longitudinal ionization of a molecular beam by an electron beam in a magnetic field

A high-efficiency ion source for a mass-spectrometer’s detector of molecular beams and their scattering products is described. The ion source is designed according to a scheme of impact ionization of a beam particle by a longitudinal electron beam in a magnetic field with a strength of up to 130 mT. The design of the source developed is very flexible and has no limitations for use in any experiments with molecular beams. An ionization efficiency of particles of an atomic helium beam of 10^?3 ions/atom has been achieved. The useful signal-to-background ratio in the detector’s chamber is 3 × 10⁴ during detection of ions with mass-to-charge ratio m/q = 4 amu.     

Measuring the effective field of biaxial anisotropy in magnetic films magnetized in their plane on pulsed induction setups

The process of 90° pulsed magnetization is proposed to be used to measure the effective field of biaxial anisotropy H _K2. The method has been developed as applied to ferrite-garnet films with a magnetization lying in their plane and is based on the determination of threshold field H _m0, at which magnetization is fully effected by rotation of magnetization vector M. The analysis performed in this study has shown that H _K2 = 4(H _m0cos?* ? H ₀sin?*)/sin4?*, where H ₀ is the setting field determining the initial direction of vector M along one of the easy magnetization axes, and ?* is the critical angle of the initial rotation of vector M reached in field H _m0, beginning with which the magnetization rotation is not decelerated by anisotropy forces. It is shown that, for typical values of H _K2, ?* ? 26°. The threshold field is determined from a kink in the dependence of the initial-peak amplitude in the longitudinal signal of 90° magnetization on the amplitude of magnetizing field H _m. For homogeneous films, the measurement accuracy of the effective field of biaxial anisotropy ensured in this method is no worse than 5–6%.     

Simultaneous magneto-optical Kerr effect and Sixtus-Tonks method for analyzing the shape of propagating domain walls in ultrathin magnetic wires

The controlled nucleation and propagation of magnetic domain walls in ultrathin ferromagnetic wires, such as nanowires and submicrometer wires, is extremely important for the development of new high performance magnetic domain wall logic devices. Therefore, it is equally essential to possess adequate advanced experimental investigation techniques in order to be able to achieve a comprehensive in situ analysis of as many as possible parameters related to the domain wall propagation, e.g., wall shape besides wall velocity and position. In this paper, we report on a method developed specifically for the investigation of the shape of propagating magnetic domain walls in ultrathin magnetic wires, i.e., with the diameter of the magnetic wire in the range 100-950 nm. The newly developed experimental method is based on the simultaneous use of two full-fledged experimental techniques: the magneto-optical Kerr effect for analyzing the surface effects of the passing domain wall and the Sixtus-Tonks method for the investigation of the entire moving wall. The results obtained offer essential information about the shape of the propagating magnetic domain walls, being unique to this new method.     

Imaging an optical disc by the combined use of scanning tunnelling microscopy and scanning electron microscopy

We present the data obtained by scanning tunnelling microscopy combined with scanning electron microscopy of the digitally encoded structure on a stamper used to fabricate optical discs. The combination allows us to focus the STM tip on a preselected spot with a precision of ?0·3 μm. The data show the superiority of STM for a more detailed characterization of shape, width, length, height and fine structure appearing on the sample. We also show the influence of tip shape on STM resolution. Simultaneous use of both microscopes is possible but high electron doses produce an insulating layer of contaminants thick enough to make STM operation impossible.     

Calculation of the induction of a constant magnetic field created in a ferromagnet by an attachable electromagnet

On the grounds of the numerical calculation of the induction of a magnetic field excited in a ferromagnet by scanners in the form of Π-shaped and solenoidal electromagnets, it is established that the Π-shaped type provides a deeper penetration of a magnetic field into a ferromagnet and its better localization in a specified volume. The induction of a magnetic field appearing under the action of a Π-shaped scanner in a ferromagnet decreased with an increase in both the thicknesses of the ferromagnet and the gap between the magnetic conductor of a scanner and the surface of a material and also depended slightly on changes in its width; a maximal scanner winding current exists, above which the induction of a magnetic field in a material changes slightly.     

Distribution of the induction of a quasi-stationary magnetic field created in a ferromagnet by an attachable electromagnet

As a result of numerical calculations, the spatial and time distributions of the induction of a quasi-stationary magnetic field, which was created in a studied ferromagnet by U-shaped and solenoidal attachable electromagnets (AEMs) at frequencies of 1 and 10 Hz, were obtained. The presence of a phase shift between the amplitude values of the magnetic-field induction at different depths in the specimen, which increases with the frequency of the exciting current, was revealed. The dependences of the magnetic-field penetration depth into the ferromagnet on the magnetic reversal frequency were studied. It was found that for the frequency range under study the magnetic-field penetration depth for both types of AEM is smaller than that for the corresponding stationary case.     

Filling the gap of a plasma opening switch with plasma from an electroexploding wire in an external magnetic field

The dynamics of filling the interelectrode gap of a plasma opening switch (POS) using an electroexploding wire with a diameter of 4 μm (tungsten) and 6 μm (carbon) is considered. The wire was connected to coaxial electrodes of the POS perpendicular to the force lines of a longitudinal magnetic field, which was created by an external source. When a current was transmitted through the wire, the longitudinal speed of produced plasma was ≈10⁶ cm/s, and the azimuthal speed was ≈10⁷ cm/s (for tungsten) and ≥1.3 × 10⁷ cm/s (for carbon). As a result, a plasma “washer” was formed and the total quantity of particles in it was determined by the parameters of the wire and the POS gap. This result is the first step in a solution of “the first shot” problem.     

Investigation of the amplification of an electromagnetic field at the end wall of a conducting thin-wall body during its interaction with an alternating magnetic field

The results of theoretical and experimental studies on an electromagnetic field are presented and qualitative and quantitative estimates of the field amplification at the end of a conducting plate due to its interaction with an alternating (traveling) magnetic field are given for the development of the eddy-current testing of conducting thin-wall bodies.     

Revisiting the free transverse vibration of embedded single-layer graphene sheets acted upon by an in-plane magnetic field

Murmu et al. [23] recently presented a nonlocal model for the transverse vibration of simply supported graphene sheets in the presence of a unidirectional in-plane magnetic field. Further studies showed that the majority of Lorentz’s force components were improperly provided and led to invalid governing equations. To remove such deficiencies, the most general form of Lorentz’s force components is carefully extracted in the present work. The nonlocal equations of motion of the problem are reconstructed and solved again. The influences of crucial parameters on the flexural frequencies of magnetically affected graphene sheets and nanoribbons are examined in detail. Furthermore, the crucial discrepancies between the results obtained in this study and those of the abovementioned previous work are rationally discussed. Some erroneous results of the latter are also rectified.     

NMR stabilization of the magnetic field by a III1-1 magnetic inductometer in the frequency modulation mode

As applied to the problem of stabilizing the magnetic field of the NMR relaxometer-diffusiometer by a III1-1 magnetic inductometer, we propose a simple method for changing the III1-1 magnetic inductometer to the frequency modulation mode to exclude the field modulation arising from modulating coils of the III1-1 sensor at the studied sample location. Original Russian Text ? A.V. Anisimov, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 4, pp. 177–178.     

The coupled effect of magnetic field,electric field,and electrolyte motion on the material removal amount in electrochemical machining

Electrochemical machining (ECM) has a strong advantage in dealing with difficult-to-machine materials and complex shaped parts. In order to improve machining accuracy, some researchers, based on the principle of interactions between the magnetic field and electric field, proposed the magnetic field-assisted ECM technology that is advantageous in improving surface roughness and facilitating material removal amount. Pitifully, little attention has been attached to effects of the coupled magnetic field, electric field, and electrolyte motion on the amount of materials removed. This paper aims to find out how arrangements of magnetic fields and coupled of the three energy (which were magnetic field, electric field, and electrolyte motion) will work on the amount of material removed in ECM. Here established a Navier-Stokes equation and a model of material removal amount in the anode under the electromagnetic field. Physical and mathematical models of the electrolyte’s flow characteristics and material removal amount were constructed through the COMSOL Multiphysics software, and simulations were carried out. An experiment was implemented to test models and the simulations. Simulation results indicated that different arrangements of the magnetic field had delivered different impacts on flow characteristics of the flow field and material removal amount. Experiment results revealed that the material removal amount had increased regardless of arrangements of magnetic fields and that the flow rate of the electrolyte had played a role in this connection. The study involved in this paper showed that the introduction of the magnetic field worked favorably to lift the material removal amount and that arrangements of magnetic fields also had the same effect in this regard. Also, it was found that a growing flow rate of the electrolyte had hindered the increases of the material removal amount.     

Study on the flow features of lead-lithium MHD splitting flows under an external magnetic field with arbitrary orientation

Journal of Mechanical Science and Technology - The understanding of magnetohydrodynamic phenomena associated with the flow of electrically-conducting fluid in complex ducts is important and...     

Solution of the inverse problem of creating a uniform magnetic field in coercimeters with partially closed magnetic systems

The use of a hybrid optimization technology by a swarm of particles with the evolutionary formation of swarm composition is considered together with the method of spatial integral equations in the synthesis of axially symmetric magnetic systems of coercimeters that contain ferromagnetic elements. The required uniformity of the magnetic field in the working volume is ensured by the optimal selection of the shape of pole pieces of a magnetizing device. A number of measures are proposed that allow acceleration of the synthesis process owing to shortening of the time spent for solving the problem of analyzing the distribution of the magnetic field in the working volume of the coercimeter.     

Dependence of the magnetic permeability on the polar coordinate in cylindrical specimens placed in an alternating homogeneous field

A solution of an electrodynamics problem regarding determination of the signal from a pickup coil with a cylindrical specimen having varying magnetic permeability that is placed into the coil is obtained as a function of the polar coordinate. The case of an alternating homogeneous field is considered. Computational models are suggested for studying the experimental dependences; these models allow one to make conclusions on the regularities of changes in the magnetic permeability in alternating fields. The appropriate plots are presented.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 77–89.Original Russian Text Copyright © 2004 by Dyakin, Sandovskii, Dudarev.