Showing papers on "Magneto published in 2011"

Magnetic pulse generation for high-speed magneto-optic switching

Abstract: In this article, the magnetic pulse characteristics needed to achieve high-speed magneto-optic (MO) switching are investigated. A fiber-based, MO, low-voltage optical switch capable of 200 ns switching is presented, along with the special circuit characteristics for magnetic field generation for high-speed switching. The switch consists of the optical system, the MO material (bismuth substituted iron garnet [(Bi1.1Tb1.9)(Fe4.25Ga0.75)O12]), and a high-speed magnetic field driving circuit. A Faraday rotator is placed within the interferometric loop of a fiber-optic Sagnac interferometer, and interference at the output ports is controlled by the applied field. The fast switching speed is accomplished via the special design of the magnetic pulse generation circuitry. The applied magnetic field overshoots the field necessary to achieve the desired Faraday rotation and then settles to a steady state field. If the duration of the overshoot is less than the time it takes the material to saturate, a fast optical ...

An anisotropic magneto resistive sensor with set/reset field.

Abstract: Using a set/reset magnetic field, an anisotropic magneto resistive (AMR) magnetic field sensing system was developed to reduce the low frequency noise of an AMR sensor. The magnetic field resolution of the AMR sensor was improved by about three times at the frequencies below 30 Hz and a magnetic field resolution of about 150 pT/√Hz was obtained at 1 Hz. For magnetic particle detection using an AMR sensor with set/reset method, the thermal disturbance effect was canceled well and the signal-to-noise ratio was improved by about three times.

Mechanism of pulse magneto-oscillation grain refinement on pure Al

Abstract: Female, born in 1973, is now the lecturer of College of Science in Shanghai University. She obtained her bachelor’s degree from Henan University in 1996 and Ph.D’s degree from Shanghai University in 2010. Her research interests mainly focus on metal solidification and biophysics. Her academic research has led to the publication of more than 12 papers. E-mail: peining@staff.shu.edu.cn Correspondant author: Zhai Qijie E-mail: qjzhai@shu.edu.cn Received: 2010-04-22; Accepted: 2010-12-25 *Pei Ning Pei Ning, Gong Yongyong, Li Renxing, Xia Zanqi and *Zhai Qijie (1. College of Science, Shanghai University, Shanghai 200444, China; 2. Shanghai Key Laboratory of Modern Metallurgy & Materials Processing, Shanghai University, Shanghai 200072, China)

Exact Solution of Transient Thermal Stress Problem of a Multilayered Magneto-Electro-Thermoelastic Hollow Cylinder

Abstract: This paper presents the theoretical analysis of a multilayered magneto-electro-thermoelastic hollow cylinder under unsteady and uniform surface heating. We obtain the exact solution of the transient thermal stress problem of the multilayered magneto-electro-thermoelastic hollow cylinder in the plane strain state. As an illustration, we perform numerical calculations of a two-layered composite hollow cylinder made of piezoelectric and magnetostrictive materials and investigate the numerical results for temperature change, displacement, stress, and electric and magnetic potential distributions in the transient state. Furthermore, the effects of the coupling, stacking sequence and position of the interface on the stresses, electric potential and magnetic potential are investigated.

On Magneto Convection in a Mushy Layer

Abstract: The subject of the title is briefly discussed and clarified based on the available experimental evidence.

Magneto-thermo-mechanical modeling of a Magnetic Shape Memory Alloy Ni-Mn-Ga single crystal

Abstract: In the frame of Thermodynamics of irreversible process, a model describing the thermomagneto-mechanical behavior of a single crystal of Ni-Mn-Ga is built. The choice of internal variables is linked to the physics of the problem (fraction of martensite variants, fraction of Weiss domains, magnetization angle). The simulations permit to describe the paths in the space (stress, temperature, magnetic field) in agreement with experimental tests. A special attention will be devoted to the control laws required to use these functional materials as sensors or actuators.

Development of a Surface Magneto-Transport Measurement System with Multi-Probes and the In situ Measurement of Bi Nanofilms Prepared on Si(111)7×7

Abstract: We have developed an independently-driven double probe-stage system that enables in situ magneto-transport measurements on surfaces and ultrathin films, prepared in ultrahigh vacuum. The measurements can be made at temperature down to 7.6 K and under magnetic field up to 7 T. The demonstration of Bi(001) crystal nanofilms on the Si(111)7×7 surface is presented.

AC Magnetic Measurements on Superconductors: Design of a Device for Magneto-Thermal Measurements

Abstract: This work describes the design and realisation of an apparatus to measure simultaneously the AC magnetic properties and the temperature distribution on the top surface of bulk superconducting samples up to 32 mm in diameter in cryogenic conditions temperature range 78-120 K. First the authors describe the experimental set-up used for simultaneous thermal and magnetic characterization of the sample. Next, the authors describe the practical considerations required for generating the large AC magnetic fields, possibly in the presence of DC fields. Then the authors present the data acquisition system allowing both temperature and magnetic data to be recorded at high a sampling rate." The performances and limitations of the system are discussed.

Manufacturing method of magneto-optic current transducer

Abstract: The invention discloses a magneto-optic current transducer and a manufacturing method thereof. The magneto-optic current transducer comprises a light source, a polarizer, a magneto-optic transducer unit, an analyzer and a direction detector which are arranged along the light path, wherein the magneto-optic transducer unit is of an overlapped growth structure composed of a protective layer, a permanent magnetic film and a magneto-optic material layer; the manufacturing method thereof is implemented by firstly preparing clean and dry magneto-optic material, then growing the permanent magnetic film on the magneto-optic material in vacuum, sequentially growing SiN or SiO2 film protective layer on the permanent magnetic film, and finally magnetizing the permanent magnetic film of the magneto-optic transducer unit by using a permanent magnetic machine. The invention uses the permanent magnetic film so that the light path passes through a strong magnetic field and has good parallel degree, thus effectively increasing rotation angle of polarized light and enhancing induction accuracy of the transducer. In addition, the magneto-optic current transducer has less light path elements, more simple and convenient system design, and higher reliability.

A Comment on "On Magneto Convection in a Mushy Layer" by D. N. Riahi

Abstract: The impracticality of MHD convection in a porous medium is further clarified.

Stray Capacitance of a Magneto Cumulative Generator Including $N$ -Turn, Single-Layer, Solid, and Round Conductor With Insulating Coating

Abstract: This paper presents a new method to calculate stray capacitance of coil turns of magneto flux cumulative generator. The proposed method depends on the coil geometrical properties. The presented analysis in this paper is based on the calculation of capacitance between two adjacent turns and capacitance between the coil turns and the central cylindrical liner of the generator for a single-layer coil with N series turns having an integrated round cross section. Moreover, the effects of the insulating coating of winding, winding pitch, distance of coil turns to the central cylindrical liner on the stray capacitance, and the sensitivity analysis of effective parameters in the creation of stray capacitance between coil turns and also between coil turns and the central cylindrical liner are considered in this paper. Simulation results show that the proposed method is very useful for the designing geometrical structure of the magneto cumulative generator coil.

Two-way Gray code magnetic encoder

Abstract: The utility model discloses a two-way Gray code magnetic encoder, including a collecting device I, a collecting device II and a power supply, the collecting device I includes a magneto sensor I and a microprocessor I, the collecting device II includes a magneto sensor II and a microprocessor II, the magneto sensor I is connected with the microprocessor I, the microprocessor I receives magnetic variation sensing signals collected by the magneto sensor I, the magneto sensor II is connected with the microprocessor II, the microprocessor II receives magnetic variation sensing signals collected y the magneto sensor II, and the power supply provides power for the magneto sensors and the microprocessors. By means of the two-way Gray code magnetic encoder, a detection signal is processed by the magneto sensors and the microprocessors to form two-way encode data with less repeat error rate, a two-way completely-independent data processing system and a power supply system avoid interfere effectively, stability of detection is improved, and a technical problem of great volume of the optical encoder is overcame.

Magneto-Mechanical Energy Conversion in Magnetic Shape Memory Alloys

Abstract: Magnetic Shape Memory (MSM) alloys present a novel means of transforming electric energy into mechanical work via the intermediate generation of magnetic field from electric current. They thereby follow a similar path of energy conversion as classical electromagnets. In this paper we will compare known designs of MSM actuators and electromagnets and discuss their characteristics based on properties of available MSM materials.

Optimization of a magnetic flux leakage measurement set---up using FEM---Simulations

Abstract: This paper describes simulations of magnetic field strength distributions for magneto---conductive material in order to be able to optimize a measurement set---up that should be capable to detect minute changes of the magnetic field strength at the surface of a specimen containing some kind of material inhomogeneities or anisotropies of magnetic properties. The sensitivity which ultimately is limited by the noise figure of the sensing effect (GMR = giant magneto resistive effect) can be evaluated with respect to the detection of deviations in eddy current patterns caused by inhomogeneities of the material's conductivity or the anisotropy of magnetic properties of the specimen's material.

Multi-Physics Interactions for Coupled Thermo-Electro-Magneto-Mechanical Effects

Abstract: ....................................................................................................................... ii ACKNOWLEDGMENTS ................................................................................................. iv VITA ................................................................................................................................... v FIELDS OF STUDY........................................................................................................... v LIST OF TABLES ........................................................................................................... viii LIST OF FIGURES ........................................................................................................... ix CHAPTER 1: Multi-Physics Interactions ........................................................................... 1 1.

Magnetic recording apparatus

Abstract: A magnetic recording apparatus includes a magnetic recording medium that is provided with a first magnetic layer with magneto crystalline anisotropy energy, a second magnetic layer with magneto crystalline anisotropy energy that is smaller than the magneto crystalline anisotropy energy of the first magnetic layer, and a nonmagnetic metal layer that is positioned between the first magnetic layer and the second magnetic layer and that provides coupling force between the first magnetic layer and the second magnetic layer; and a magnetic head that includes a main pole that applies a recording magnetic field in a direction perpendicular to a film surface of the magnetic recording medium to the magnetic recording medium, and an alternate current (AC) magnetic field generator that applies an AC magnetic field with a frequency of 1-40 GHz to the magnetic recording medium.

Three-dimensional magneto-resistive random access memory devices based on resonant spin-polarized alternating currents

Abstract: Selective switching of a magneto-resistive random access memory (MRAM) multilayer stack is demonstrated using resonant spin-polarized alternating currents (AC) superimposed on spin-polarized direct currents. Finite element micromagnetic simulations show that the use of frequency triggered AC allows one to maximize the transferred spin transfer torque selectively in order to merely reverse the magnetization of a single storage layer in a stack. Using layers with different resonance frequencies, which are realized by altering the anisotropy constants, allows one to address them by tuning the AC frequency. A rapid increase of the storage density of MRAM devices is shown by using three-dimensional sandwich structures.

Research on Magneto Window Antenna for Improving Propagation Characteristic of Electromagnetic Wave in Plasma Sheath

Abstract: The communication blackout,caused by plasma sheath around a hypersonic vehicle flying in atmosphere is a problem to aerospace vehicles.A magneto window will be formed when a static magnetic field is applied to plasma sheath,and it can be used to reduce the attenuation of right circularly polarized wave in the sheath.The best way to build the magnetic window is by use of superconductive devices.However,there are some problems such as heavy weight and complex structure in use for superconductive devices to generate a magneto window.In this paper,an integrated concept,i.e.magneto window antenna,is proposed.A circular polarized GPS antenna is designed according to this concept.The antenna patch was made of copper and the ground plate is made of rare earth magnet NdFeB.The magnet will work as a part of antenna and be used to produce a strong magnetic field for magneto window as well.Radiation pattern and magnetic field intensity surrounding the antenna are analyzed by numerical simulation.It is shown that the attenuation of right circularly polarized wave through plasma sheath is reduced obviously.

The integral magneto-refractive effect: A method of probing magneto-resistance

Abstract: We show that the optical infrared magneto-refractive effect can be used to probe magneto-resistance effects in absolute terms. A spin valve sample with synthetic anti-ferromagnet has been studied using non-contact infrared reflection spectroscopy measurements. Direct experimental comparison shows excellent agreement between electrical and optical measurements in both shape of the magneto-resistance curves and absolute values. This opens the possibility of developing fast and efficient tests of magneto-resistive samples and sensors using an in situ, non-contact, non-destructive optical approach, without the need to determine a calibration factor between the electrical and optical measurements.

Magneto resistive voltage biasing scheme with fast recovery and maximum dynamic range

Abstract: A system and method for providing a fast recovery for voltage bias applied to an MR sensor, when a voltage is applied to the MR sensor very quickly while the MR sensor transitions from an idle or sleep state to an active state includes an apparatus and method for adjusting the voltage and range applied to the MR sensor. The apparatus includes a circuit having a current biasing circuit for supplying a current bias to a transducer, a voltage biasing circuit configured to supply a voltage bias to a transducer, and a charge pump for maintaining the current bias and the voltage bias at the maximum range so that the voltage at the transducer is maximized. The method includes specifying the magneto resistive biasing voltage, measuring a resistance of the magneto resistive sensor, setting an internal reference resistance value to be near the measured resistance of the magneto resistive sensor, determining a code that specifies the amount of current that flows through the magneto resistive sensor, flowing current through the magneto resistive sensor by turning on a digital to analog converter adjustable resistor.