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1 Apr 2012

Volume 111, Issue 7, Articles (07xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 111, 071101 (2012); http://dx.doi.org/10.1063/1.3694674 (23 pages)

Shunfeng Li and Andreas Waag
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back to top Motors, Actuators, Transformers, Electrical Machines

Sensor-less pseudo-sinusoidal drive for a permanent-magnet brushless ac motor

Li-Hsiang Liu, Tzuen-Lih Chern, Ping-Lung Pan, Tsung-Mou Huang, Der-Min Tsay, and Jao-Hwa Kuang

J. Appl. Phys. 111, 07E701 (2012); http://dx.doi.org/10.1063/1.3669848 (3 pages)

Online Publication Date: 3 February 2012

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The precise rotor-position information is required for a permanent-magnet brushless ac motor (BLACM) drive. In the conventional sinusoidal drive method, either an encoder or a resolver is usually employed. For position sensor-less vector control schemes, the rotor flux estimation and torque components are obtained by complicated coordinate transformations. These computational intensive methods are susceptible to current distortions and parameter variations. To simplify the method complexity, this work presents a sensor-less pseudo-sinusoidal drive scheme with speed control for a three-phase BLACM. Based on the sinusoidal drive scheme, a floating period of each phase current is inserted for back electromotive force detection. The zero-crossing point is determined directly by the proposed scheme, and the rotor magnetic position and rotor speed can be estimated simultaneously. Several experiments for various active angle periods are undertaken. Furthermore, a current feedback control is included to minimize and compensate the torque fluctuation. The experimental results show that the proposed method has a competitive performance compared with the conventional drive manners for BLACM. The proposed scheme is straightforward, bringing the benefits of sensor-less drive and negating the need for coordinate transformations in the operating process.
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84.50.+d Electric motors
84.30.Ng Oscillators, pulse generators, and function generators
89.20.Kk Engineering

Magnetic navigation system for the precise helical and translational motions of a microrobot in human blood vessels

S. M. Jeon, G. H. Jang, H. C. Choi, S. H. Park, and J. O. Park

J. Appl. Phys. 111, 07E702 (2012); http://dx.doi.org/10.1063/1.3671411 (3 pages)

Online Publication Date: 7 February 2012

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Different magnetic navigation systems (MNSs) have been investigated for the wireless manipulation of microrobots in human blood vessels. Here we propose a MNS and methodology for generation of both the precise helical and translational motions of a microrobot to improve its maneuverability in complex human blood vessel. We then present experiments demonstrating the helical and translational motions of a spiral-type microrobot to verify the proposed MNS.
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45.40.Ln Robotics
85.70.Rp Magnetic levitation, propulsion and control devices

Enhancing and broadening absorption properties of frequency selective surfaces absorbers using FeCoB-based thin film

Wenyi Ren, Yan Nie, Xuan Xiong, Cui Zhang, Yan Zhou, and Rongzhou Gong

J. Appl. Phys. 111, 07E703 (2012); http://dx.doi.org/10.1063/1.3670980 (3 pages) | Cited 1 time

Online Publication Date: 10 February 2012

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In this paper, the influence of FeCoB-based magnetic film on the absorption properties of traditional frequency selective surface (FSS) was investigated experimentally. A single-layer Minkowski fractal planar frequency selective surface was chosen, and the laser etching technique was proposed to fabricate aluminum-based FSS (AFSS) samples. Magnetic films were prepared by radio frequency magnetron sputtering, with the targets of Fe40Co40B20 and SiO2. It is found that after the magnetic film is incorporated, the bandwidth under −10 dB increases by 33.3% from 5.08 to 6.78 GHz and the peak value of reflectivity decreases from −12.46 to −38.41 dB. The 3.1-mm-thick radar absorber is relatively light and could obtain the reflectivity of −38.41 with −20 dB bandwidth of 1.85 GHz. As a consequence, under the circumstance that the total thickness of the sample maintains relatively constant, the magnetic thin film can effectively improve the absorption properties of the sample.
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75.70.Ak Magnetic properties of monolayers and thin films
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.65.Cf Surface cleaning, etching, patterning
81.15.Cd Deposition by sputtering

Analytical study and corresponding experiments for a new resonant magnetic charger with circular spiral coils

Junhua Wang, Jiangui Li, S. L. Ho, W. N. Fu, Zhigang Zhao, Weili Yan, and Mingui Sun

J. Appl. Phys. 111, 07E704 (2012); http://dx.doi.org/10.1063/1.3670981 (3 pages)

Online Publication Date: 10 February 2012

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This study proposes a new resonant magnetic charger comprising circular spiral coils that operate with a strong coupling effect between the transmitter and the receiver. The two spiral coils are fitted with additional copper tapes to serve as resonant transmitter and receiver coils. The magnetic flux distributions are calculated using temporal coupled mode theory. Analysis results show that the proposed system can dramatically improve the efficiency and extend the power transfer distance. Experiments have been carried out in order to verify the performance of the system. In particular, the trends of output voltages when either the operating frequencies or the transfer distances are changing are reported. The system efficiency obtained experimentally is also given. Both calculated and measured results are in good agreement.
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85.70.-w Magnetic devices

Fabrication of a fully magnetic impeller for improvement of the magnetic properties of a pump with a power harvester

Sung Hoon Kim, Jaewon Shin, Shuichiro Hashi, Kazushi Ishiyama, Masaru Ozaki, and Syuji Matsumura

J. Appl. Phys. 111, 07E705 (2012); http://dx.doi.org/10.1063/1.3670983 (3 pages) | Cited 1 time

Online Publication Date: 10 February 2012

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An all-in-one wireless pump with a power generator was developed for use in biomedical applications. The developed pump is driven by an external rotating magnetic field. Thus, the performance of the system is limited by the magnetic properties of the rotor. To improve the magnetic properties of the magnetic all-in-one pump, a fully magnetic impeller was fabricated with magnetic powder (Sm2Fe17N3) because sintered magnetic materials have a lower degree of freedom for shape. The magnetic moment (M) and coercive force (Hc) of the fully magnetic impeller are 0.993 Am2 and 0.82 MA/m, respectively. We analyzed the magnetic properties of the fully magnetic impeller using simulation and experiments. In addition, we investigated the improved performance of the all-in-one pump system using the fully magnetic impeller.
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85.70.-w Magnetic devices

Modeling and analysis of a magnetically levitated synchronous permanent magnet planar motor

Baoquan Kou, Lu Zhang, Liyi Li, and Hailin Zhang

J. Appl. Phys. 111, 07E706 (2012); http://dx.doi.org/10.1063/1.3671424 (3 pages)

Online Publication Date: 13 February 2012

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In this paper, a new magnetically levitated synchronous permanent magnet planar motor (MLSPMPM) driven by composite-current is proposed, of which the mover is made of a copper coil array and the stator are magnets and magnetic conductor. The coil pitch τt and permanent magnet pole pitch τp satisfy the following relationship 3nτt = (3n ± 1)τp. Firstly, an analytical model of the planar motor is established, flux density distribution of the two-dimensional magnet array is obtained by solving the equations of the scalar magnetic potential. Secondly, the expressions of the electromagnetic forces induced by magnetic field and composite current are derived. To verify the analytical model and the electromagnetic forces, finite element method (FEM) is used for calculating the flux density and electromagnetic forces of the MLSPMPM. And the results from FEM are in good agreement with the results from the analytical equations. This indicates that the analytical model is reasonable.
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84.50.+d Electric motors
85.70.Rp Magnetic levitation, propulsion and control devices
02.70.Dh Finite-element and Galerkin methods

Characteristic and magnetic field analysis of a high temperature superconductor axial-flux coreless induction maglev motor

Qin Wei, Fan Yu, Fang Jin, Li Shuo, Li Guoguo, and Lv Gang

J. Appl. Phys. 111, 07E707 (2012); http://dx.doi.org/10.1063/1.3671783 (3 pages)

Online Publication Date: 15 February 2012

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A new high temperature superconductor axial-flux coreless maglev motor (HTS AFIM) is proposed, of which the primary windings are made of HTS tapes and the secondary is a non-magnetic conductor. The main works of this paper are the magnetic-field computation and characteristics analysis of HTS AFIM. For the first one, the reduction of magnetic fields near outer and inner radius of the HTS AFIM is solved by introducing the sub-loop electro-magnetic model along the radial position. For the second one, the AC losses of HTS coils are calculated. The relationships between the device’s characteristics and device parameters are presented, and the results indicate that under certain frequency and current levitation device can output enough lift force. The conclusions are verified by finite element calculations.
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84.71.Ba Superconducting magnets; magnetic levitation devices
84.50.+d Electric motors
84.71.Mn Superconducting wires, fibers, and tapes
85.70.Rp Magnetic levitation, propulsion and control devices

Electromagnetic design analysis and performance improvement of axial field permanent magnet generator for small wind turbine

Tae-Uk Jung

J. Appl. Phys. 111, 07E708 (2012); http://dx.doi.org/10.1063/1.3672060 (3 pages)

Online Publication Date: 22 February 2012

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Axial field permanent magnet (AFPM) generators are widely applied for the small wind turbine. The output power of conventional AFPM generator, AFER-NS (Axial Field External Rotor–Non Slotted) generator, is limited by the large reluctance by the long air-gap flux paths. In this paper, the novel structure of AFPM generator, AFIR-S (Axial Field Inner Rotor–Slotted) generator, is suggested to improve the output characteristics. The electromagnetic design analysis and the design improvement of the suggested AFIR-S generator are studied. Firstly, the electromagnetic design analysis was done to increase the power density. Secondly, the design optimizations of the rotor pole-arc ratio and skew angle to increase the output power and to reduce the cogging torque. Finally, the output performances of AFER-NS and AFIR-S generator are compared with each other.
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88.50.G- Wind turbines
84.50.+d Electric motors

Transient analysis and control of bias magnetic state in the transformer of on-line pulse-width-modulation switching full bridge direct current-direct current converter

Jiaxin Chen, Youguang Guo, Jianguo Zhu, and Zhi Wei Lin

J. Appl. Phys. 111, 07E709 (2012); http://dx.doi.org/10.1063/1.3672068 (3 pages)

Online Publication Date: 22 February 2012

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This paper presents a finite element analysis (FEA) based method for analyzing and controlling the bias magnetic state of the transformer of a pulse-width-modulation (PWM) switching full bridge dc-dc converter. A field-circuit indirect coupling method for predicting the transient bias magnetic state is introduced first. To increase flexibility of the proposed method, a novel transformer model which can address not only its basic input-output characteristic, but also the nonlinear magnetizing inductance, is proposed. Both the asymmetric characteristic and the variable laws of the current flowing through the two secondary windings during the period of PWM switching-off state are highlighted. Finally, the peak magnetizing current controlled method based on the on-line magnetizing current computation is introduced. Analysis results show that this method can address the magnetic saturation at winding ends, and hence many previous difficulties, such as the start-up process and asymmetry of power electronics, can be easily controlled.
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84.30.Jc Power electronics; power supply circuits
02.70.Dh Finite-element and Galerkin methods

Design of a spoke-type permanent-magnet motor with optimal winding configuration for electric vehicle applications

Qian Chen, Guohai Liu, Wensheng Gong, Li Qu, Wenxiang Zhao, and Yue Shen

J. Appl. Phys. 111, 07E710 (2012); http://dx.doi.org/10.1063/1.3672077 (3 pages)

Online Publication Date: 22 February 2012

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The spoke-type motor has higher torque density than the conventional one resulting from its structure for concentrating flux from permanent magnets (PMs). However, this motor suffers from the serious distortion of back electromotive force (EMF). This paper proposes a cost-effective approach to design a spoke-type motor with lower harmonics of back-EMF for electric vehicle. The key is to superimpose the coil-EMF of one phase in such a way that the harmonics of the phase-EMF can be canceled, resulting in essentially sinusoidal waveforms. By using finite element method (FEM), an optimal coil-EMF vectors distribution for minimum harmonics of the phase-EMF is obtained and verified. In addition, the co-simulation technology is adopted to verify that the torque ripple under the optimal winding configuration can be significantly suppressed.
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88.85.Hj Electric vehicles (EVs)
84.50.+d Electric motors
02.70.Dh Finite-element and Galerkin methods

Investigation of a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free-piston stirling engines

Ping Zheng, Chengde Tong, Jing Zhao, Bin Yu, Lin Li, Jingang Bai, and Lu Zhang

J. Appl. Phys. 111, 07E711 (2012); http://dx.doi.org/10.1063/1.3672084 (3 pages) | Cited 1 time

Online Publication Date: 22 February 2012

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This paper investigates a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free piston Stirling engines (FPSEs). Taking the advantages of Halbach array, a 1 kW prototype alternator is designed. Considering the rms value of electromotive force (EMF) and harmonic distortion, the optimal length ratio of the axial- and radial-magnetized permanent magnets and thicknesses of the permanent magnets are optimized by 2D finite element method. The alternator detent force, which is an important factor for smooth operation of FPSEs, is studied by optimizing slot tip and end tooth. The load and thermal performances of the final design are simulated. A prototype alternator was designed, built and tested. Experimental data indicated satisfactory design.
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84.50.+d Electric motors
89.20.Kk Engineering
02.70.Dh Finite-element and Galerkin methods

Analytical magnetic torque calculations and experimental testing of radial flux permanent magnet-type eddy current brakes

Jang-Young Choi and Seok-Myeong Jang

J. Appl. Phys. 111, 07E712 (2012); http://dx.doi.org/10.1063/1.3672408 (3 pages) | Cited 1 time

Online Publication Date: 23 February 2012

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This paper reports on analytical magnetic torque calculations and experimental tests of a radial flux permanent magnet (RFPM)-type eddy current brake (ECB). Analytical solutions for permanent magnet-generated magnetic fields that consider the eddy current reaction are obtained by using a magnetic vector potential and a two dimensional (2D) polar coordinate system. On the basis of these solutions, the analytical expressions for a magnetic torque are also derived. All analytical results are validated extensively by non-linear finite element calculations. In particular, magnetic torque measurements are obtained in tests to confirm the analyses. Finally, practical issues related to the analytical study of RFPM-type ECBs are fully discussed.
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89.40.-a Transportation
75.50.Ww Permanent magnets

Design and analysis of new fault-tolerant permanent magnet motors for four-wheel-driving electric vehicles

Guohai Liu, Wensheng Gong, Qian Chen, Linni Jian, Yue Shen, and Wenxiang Zhao

J. Appl. Phys. 111, 07E713 (2012); http://dx.doi.org/10.1063/1.3672853 (3 pages)

Online Publication Date: 24 February 2012

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In this paper, a novel in-wheel permanent-magnet (PM) motor for four-wheel-driving electrical vehicles is proposed. It adopts an outer-rotor topology, which can help generate a large drive torque, in order to achieve prominent dynamic performance of the vehicle. Moreover, by adopting single-layer concentrated-windings, fault-tolerant teeth, and the optimal combination of slot and pole numbers, the proposed motor inherently offers negligible electromagnetic coupling between different phase windings, hence, it possesses a fault-tolerant characteristic. Meanwhile, the phase back electromotive force waveforms can be designed to be sinusoidal by employing PMs with a trapezoidal shape, eccentric armature teeth, and unequal tooth widths. The electromagnetic performance is comprehensively investigated and the optimal design is conducted by using the finite-element method.
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88.85.Hj Electric vehicles (EVs)
84.50.+d Electric motors

An H-module linear actuator for medical equipment applications

Xiao Liu, Keyuan Wu, Yunyue Ye, and Kaiyuan Lu

J. Appl. Phys. 111, 07E714 (2012); http://dx.doi.org/10.1063/1.3673416 (3 pages)

Online Publication Date: 27 February 2012

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An H-module linear actuator (HMLA) is proposed in this paper for medical equipment applications. Compared to the existing linear actuators used in medical equipment, the proposed H-module linear actuator has much lower normal force, which makes use of an additional air-suspension system unnecessary. The working principle of the HMLA is illustrated in detail in this paper, and its tangential and normal force characteristics are demonstrated by using finite element analysis (FEA). It is proved that the normal force of the HMLA can be greatly reduced without sacrificing the useful tangential force component.
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87.63.-d Non-ionizing radiation equipment and techniques
87.10.Kn Finite element calculations
87.85.-d Biomedical engineering

Topology selection and design optimization for magnetostrictive inertial actuators

Myounggyu D. Noh and Young-Woo Park

J. Appl. Phys. 111, 07E715 (2012); http://dx.doi.org/10.1063/1.3673431 (3 pages)

Online Publication Date: 27 February 2012

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When designing a magnetostrictive inertial actuator, it is important to minimize the amount of magnetostrictive material and permanent magnet while satisfying design requirements. In this paper, we developed a magnetic circuit model that is simple yet realistic, as verified through finite element analyses. Using this model, different actuator topologies are compared in terms of the least necessary magnet size and leakage/fringing fluxes. If the magnets are in direct contact with the magnetostrictive rod, much smaller magnets can generate the required bias level than the case where the magnets are located in the flux return path, at the cost of significant field variations inside the magnetostrictive material.
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85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices
75.50.Ww Permanent magnets

Prediction of iron losses in doubly salient permanent magnet machine with rectangular current waveform

Jianzhong Zhang, Minxi Wang, and Ming Cheng

J. Appl. Phys. 111, 07E716 (2012); http://dx.doi.org/10.1063/1.3675154 (3 pages)

Online Publication Date: 29 February 2012

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Iron losses in doubly salient permanent magnet (DSPM) machine are difficult to predict, as the flux waveforms are complex and dc bias existed. This paper measures iron losses at no load for different rotor speeds and these measured loss data are used to calibrate the iron loss model of the DSPM machine. Then the iron losses at rated load are predicted under three phase rectangular currents exerting on the armature windings. The result shows that small increment of iron losses is in the rotor at rated load which do benefit to the rotor thermal dissipation design.
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84.50.+d Electric motors

Solution to the problem of E-cored coil above a layered half-space using the method of truncated region eigenfunction expansion

Fahimeh Sakkaki and Hossein Bayani

J. Appl. Phys. 111, 07E717 (2012); http://dx.doi.org/10.1063/1.3675183 (3 pages)

Online Publication Date: 1 March 2012

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In eddy current non-destructive testing, using ferrite cores with different shapes produce interesting and very important predictions on locating underneath cracks, corrosions and flaws in conductive layers. This paper describes a method of calculating magnetic vector potential for an E-cored eddy current probe above a layered half space. The coil impedance variation with frequency and eddy currents are determined. The results of the calculations are in very good agreement with results from COMSOL.
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81.70.Ex Nondestructive testing: electromagnetic testing, eddy-current testing
84.32.Hh Inductors and coils; wiring

Development of a miniature fan motor

Chien-Chang Wang, Yeong-Der Yao, Kun-Yi Liang, Chung-Chun Huang, and Yu-Choung Chang

J. Appl. Phys. 111, 07E718 (2012); http://dx.doi.org/10.1063/1.3675993 (3 pages)

Online Publication Date: 2 March 2012

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A novel compact axial flux fan motor was developed. Such a micromotor could be a potential candidate for using as the cooling solution for the next generation mobile devices, for example, smart phones and pico-projectors. The key parameters of the motor, such as back electromotive force, cogging torque, and axial preload are predicted using finite element method. In addition, new approaches are proposed to measure these items, and the corresponding experimental results are in good agreement with the simulated one. Moreover, the undesired vibration harmonic is successfully suppressed, and the fan motor represents a high static pressure and air flow rate.
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84.50.+d Electric motors
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
02.70.Dh Finite-element and Galerkin methods

Calculation of eddy currents in magnetically nonlinear anisotropic conductors

P. McAvoy, C. Serpico, and I. Mayergoyz

J. Appl. Phys. 111, 07E719 (2012); http://dx.doi.org/10.1063/1.3675996 (3 pages)

Online Publication Date: 2 March 2012

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Exact analytical expressions for eddy currents in magnetically nonlinear isotropic conducting media can be derived in the case of circular polarizations of magnetic field. It is shown that by using the perturbation technique analytical expressions for eddy currents can be derived for magnetically nonlinear anisotropic conducting media and elliptically polarized magnetic fields.
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75.30.Gw Magnetic anisotropy

Stabilization of input impedance for wireless power supply circuit

Takahiro Misawa, Tadakuni Sato, Tetsuya Takura, Fumihiro Sato, and Hidetoshi Matsuki

J. Appl. Phys. 111, 07E720 (2012); http://dx.doi.org/10.1063/1.3676046 (3 pages)

Online Publication Date: 2 March 2012

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A wireless power supply transmits electrical energy from a power source to a load without the use of a connecting wire. There are a number of wireless power supply techniques including electromagnetic induction, electromagnetic radiation, and electrical conduction. Here, we have investigated methods that use electromagnetic induction. Typically, for electromagnetic induction, we assume that the load resistance will fluctuate during battery charging due to variations in the battery voltage. Therefore, to stabilize the electrical power supply, a steady input impedance of the transmission circuit is preferable such that the influence of load resistance fluctuations is minimized. To this end, we suggest a “series-parallel resonant circuit” for the transmission circuit that has this characteristic.
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84.30.Jc Power electronics; power supply circuits

Development of a highly efficient brushless dc motor utilizing both radial and axial air gaps

K. J. Kang, G. H. Jang, S. J. Sung, and J. H. Chang

J. Appl. Phys. 111, 07E721 (2012); http://dx.doi.org/10.1063/1.3676210 (3 pages)

Online Publication Date: 5 March 2012

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This research proposes an effective structure for a brushless dc motor utilizing both radial and axial air gaps. The proposed motor generates torque in both the radial and axial air gaps, while the conventional motor generates torque only in the radial air gap. The proposed motor was optimized to minimize the electromagnetic loss of the motor to increase the effective air gap length and fill-factor of the coil while decreasing the saturation of the core at the same time. The electromagnetic loss was reduced by 35% in comparison with a conventional motor.
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84.50.+d Electric motors

The optimization of dual-core closed-loop fluxgate technology in precision current sensor

Xiaoguang Yang, Bo Zhang, Youhua Wang, Zhigang Zhao, and Weili Yan

J. Appl. Phys. 111, 07E722 (2012); http://dx.doi.org/10.1063/1.3677200 (3 pages)

Online Publication Date: 7 March 2012

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This paper presents a new dual-core closed-loop flux gate current sensor. The mathematical model was built, and the parameters that affect the characteristics of the flux gate current sensor were analyzed. The effects of the structural parameters on output characteristics of the sensor were simulated. Based on the simulation results, a prototype was designed, and the test results have a good agreement with the simulation results. The current sensor has the advantages of ultra low nonlinear error ( ± 3‰) and low offset error. The noise in the primary current is eliminated when measuring dc or ac signal. Especially, the designed dual-core closed-loop flux gate current sensor can measure current up to 20 kHz with the nominal primary current value of ± 30 A.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
02.60.Pn Numerical optimization

Magnetic properties and high-frequency characteristics of FeCoAlO gradient composition thin films

Fu Zheng, Feilong Luo, Yuanfu Lou, Ying Wang, Jianmin Bai, Dan Wei, Xiaoxi Liu, and Fulin Wei

J. Appl. Phys. 111, 07E723 (2012); http://dx.doi.org/10.1063/1.3677655 (3 pages)

Online Publication Date: 7 March 2012

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5 × 25 mm FeCoAlO gradient composition thin film was prepared with composite target by using RF magnetron sputtering. The Al-O composition gradient along the length direction of the film was introduced by Al2O3 chips asymmetrically arrayed on a Fe70Co30 target disk. The film was divided into five equal segments. All samples showed a low coercive force Hc of 4 – 8 Oe. The saturation magnetization 4πMs increased continuously from 17.3 kGs for sample 1 (has more Al-O content) to 19.7 kGs for sample 5 and it was consistent with the increasing of Fe-Co composition. Meanwhile, these samples showed different anisotropy behaviors relating with Al-O composition. The sample 1 exhibited the same magnetization curve along the directions of G‖ and G⊥ (G‖ and G⊥ are parallel and perpendicular to the direction of the Al-O composition gradient, respectively). In both of G‖ & G⊥ directions, the sample 1 showed a resonance frequency (fr) of around 2.6 – 3.0 GHz, while, in G‖ direction, it showed a high value of real permeability μ′. The sample 5 exhibited a distinct in-plane uniaxial anisotropy and a good high-frequency response of 3.0 GHz resonance frequency. So these films having gradient composition exhibit are suggested for the use in integrated magnetic devices working in the GHz frequency range.
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75.70.Ak Magnetic properties of monolayers and thin films
81.15.Cd Deposition by sputtering
72.30.+q High-frequency effects; plasma effects
75.30.Gw Magnetic anisotropy
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Graphene oxide added carbonyl iron microsphere system and its magnetorheology under applied magnetic fields

W. L. Zhang and H. J. Choi

J. Appl. Phys. 111, 07E724 (2012); http://dx.doi.org/10.1063/1.3677671 (3 pages)

Online Publication Date: 7 March 2012

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Novel graphene oxide (GO) particle was introduced as an additive to soft magnetic carbonyl iron (CI) micron-sized particle based magnetorheological (MR) fluid to improve its sedimentation and agglomeration problems in which the MR fluid is a colloidal suspension of magnetizable particles dispersed in a nonmagnetic carrier. The added plate-like GO gap-fillers filled the interspaces of CI particles and improved the resistance to sedimentation. The MR properties of two systems with and without additives were evaluated and compared under different magnetic field strengths using a rotational rheometer. Morphology of pure CI and GO/CI mixture were examined via scanning electron microscopy (SEM) images, and X-ray diffraction (XRD) patterns confirm the differences between pure CI and GO/CI mixture further, the sedimentation problem was observed to be improved.
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82.70.Dd Colloids
82.70.Kj Emulsions and suspensions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

A novel linear and rotary Halbach permanent magnet actuator with two degrees-of-freedom

Ping Jin, Shuhua Fang, Heyun Lin, Xianbin Wang, and Shigui Zhou

J. Appl. Phys. 111, 07E725 (2012); http://dx.doi.org/10.1063/1.3677869 (3 pages)

Online Publication Date: 8 March 2012

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This paper presents a novel linear and rotary Halbach permanent magnet actuator, which is capable of two degrees-of-freedom movements. The magnetic field distributions of the actuator are analytically analyzed using the magnetic scalar potential, where its tubular mover is transferred into a planar one by using a magnetic field curvature factor. The linear cogging force and rotary cogging torque and the stator flux-linkage of the actuator are subsequently predicted validated by the three-dimensional finite element method.
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85.70.-w Magnetic devices
85.80.-b Thermoelectromagnetic and other devices
02.70.Dh Finite-element and Galerkin methods
84.50.+d Electric motors
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