Two types of Ba-ferrite particulate media used in technical demonstrations that achieved 6.7 Gbit/in² in 2007 and 29.5 Gbit/in² in 2010 were compared by focusing on differences in their magnetic particle properties and tape characteristics. The results revealed that the difference in SNR between these two media could be explained by the difference in the particle volume and the orientation of the easy axis. The difference in the surface profile of these two media affected their frictional and stictional behavior without affecting their read/write characteristics in the short wavelength region. The long-term chemical stability of Ba-ferrite particulate media was also investigated using a Battelle Class II environment. The results indicated that Ba-ferrite particulate media have superior resistance to chemical corrosion compared to conventional metal particulate media.

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  The influence of the magnetic domain of the perpendicular anisotropy master medium (PAMM) on printing characteristics is analyzed by using micromagnetic simulation. As a result, when AC-erased CoPt film makes contact with the recording layer, the magnetization of the recording layer is reversed at the position corresponding to the domain wall of the CoPt film. However, the magnetic domain has no effect on the printing characteristics in the actual printing process.

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  At high linear densities, analyzing isolated transitions is indispensable. Estimating the write/read resolution gives particularly valuable feedback that is useful in designing the head/medium. Magnetization distributions were calculated from measured waveforms by reciprocity. An iterative method, the Jacobi method, was used to suppress noise. The calculated magnetization showed a distribution between the hyperbolic tangent and arc-tangent functions.

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  Magnetic fluctuation noise due to a pinned layer (N_mag-pin) was measured to improve head-amp SNR by using fabricated heads, and the results were confirmed through micro-magnetic simulations. An experiment revealed that the N_mag-pin decreased as exchange coupling J_k and/or sensor aspect ratio (SH/Twr) increased. These results were consistent with the simulated ones. Reduced N_mag-pin was expected by both increasing J_k and larger SH/Twr. The simulations indicated that the head with J_k∼1.3 erg/cm² suppressed most N_mag-pin, and demonstrated improved head-amp SNR around 1 dB.

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  Magnetic Properties of the Nd-Fe-B micro-wires prepared by in-rotating liquid spinning process (IRLSP) was studied. The coercive force of the wire sample was enhanced by using the nozzle, which has the small orifice of 0.1 mm. Hard magnetic properties of the wire samples were also improved by post-annealing of 600°C for 2 hours in vacuum. It is considered that enhancement of the coercive force of the wire is caused by crystallization of the 2:14:1 phase. In addition, by adding 7.5 at.% Tb, the hecoercive force was increased and became about 1 kOe in the maximum.

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  Magnetic anisotropy energy (MAE) is obtained in the frame of a first principles calculation for L1₀ type FeNi alloy. The L1₀ type FeNi is only found in the iron meteorite in the nature that has an extraterrestrial texture called a Widmanstätten structure. The presence of L1₀ FeNi influences the unusual domain structure referred as “head-on”, in which the magnetization in alternate domains runs with each other. This magnetic domain is provided due to the large anisotropy in the L1₀ lamella at the interface between the α-and γ-phase in the FeNi alloy. In the present study, the MAE of L1₀ FeNi is calculated as a function of the c/a ratio for the lattice distortion by using the LMTO-ASA formula. The result indicates that the distortion enlarges the MAE when c/a < 1.0

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  This paper presents the results obtained from a fundamental study on eddy-current linear encoders. We propose eddy current linear encoders as a replacement for optical and magnetic encoders. Eddy current linear encoders are linear displacement and position sensors that are used in eddy-current tests. Linear displacement and position are detected by counting cracks on a scale from the change in the induced voltage of the detecting coil. They are expected to have unique advantages in reducing costs and enabling shields and gaps to be used between the detector and scale. We report experimental results on the output characteristics of an eddy current linear encoder and the characteristics of the gap between the coil and scale. The effects of the ferrite core, the effects of ferrite size, and the output characteristic of a 1-mm pitch scale obtained by simulation are also reported.

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  Magnetic force microscopy (MFM) using an FePt high coercivity probe and Q-control in vacuum enabled an accurate magnetic domain evaluation without changing of probe magnetization in observation of Nd-Fe-B sintered magnets. The effectiveness of this technique to conventional MFM was confirmed with magnetized sample by 50 kOe pulse field and thermally demagnetized sample. And an in-situ thermal demagnetization observation of the Nd-Fe-B sintered magnets succeeded using temperature-controlled MFM.

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  A position-detecting system made up of a nasogastric tube using a wireless LC resonated magnetic marker has been developed. The marker, consisting of an inductor and a capacitor without battery or electric wires, was installed inside a commercial nasogastric tube. A positioning accuracy within 7.1mm was obtained when the marker inside the tube was parallel translation to 100mm. The marker inside the tube was roughly tracked in the esophagus and trachea of a human model.

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  A highly sensitive method of obtaining the permeability of magnetic film without limitations in sample size was developed based on the electrical impedance of magnetic film in contact with microstrip meander lines. The permeability of a CoNbZr thin film (25 × 25 mm, 0.1-μm thick) was evaluated in a frequency range of 100 MHz-8 GHz; the measured values roughly corresponded to those obtained with the Landau-Lifshitz-Gilbert equation. The proposed method shows promise for measuring the permeability of wafer-sized samples because it is not restricted by size limitations.

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  We have developed a very sensitive transmission line-type thin film sensor. The sensor, consisting of a coplanar line, SiO₂ film, and amorphous CoFeSiB film, was fabricated by sputtering, lift-off, and lithography processes. A phase change of 45 degrees/Oe was obtained at 1 GHz. We arranged two-dimensional stepping motors and developed a scanning system for the sensor. Aluminum samples with through holes were examined by using the eddy current method. Aluminum wires with small Fe balls as impurities were tested by measuring the DC field.

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  High-density printed circuit boards (PCBs) with less than 50 μm/50 μm line/space has been developed. Since the spacing between adjacent signal lines becomes very narrow in the PCBs, the crosstalk from electromagnetic interference in adjacent lines becomes serious. The authors have proposed a magnetic method of reducing the crosstalk. PCBs with electroless-plated Ni-P alloy film on the signal lines were fabricated. From an experiment using a PCB-TEG with a 130 μm/50 μm line/space and 25-mm line length, crosstalk was suppressed throughout a wide frequency range. In using 6-μm thick Ni₉₈P_2.0 (wt.%) alloy film, the suppressed crosstalk was up to 12 dB around 1 GHz. However, the influence of transmission and reflection in the main signal line was very small.

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  We propose a micro-energy harvesting device using an iron gallium alloy (Galfenol) that is capable of providing electrical energy through environmental vibrations. Galfenol is a ductile magnetostrictive material with high piezomagnetic constant, good machinability, and a large inverse magnetostrictive effect in which the magnetization can be varied by mechanical stress. The proposed device consists of two columns of Galfenol those ends are connected at the end with iron yokes, coils and a bias magnet. When bending force is applied on the mover with the other end fixed like a cantilever, the magnetization in one column increases because of tensile force due to the inverse magnetostrictive effect, and the other decreases due to compression. The time variation of the magnetization generates voltage on the wound coils. This energy harvesting device is advantageous over other types such as those using piezoelectric material, in size, high robustness, and low electrical impedance. In addition, the two columns structure requires low mechanical force to provide sufficient stress to change the magnetization. We fabricated a prototype using stress-annealed Galfenol with 314 coil turns and in experiments verified a maximum voltage of 0.48 V at forced vibration with a frequency of 333 Hz. The frequency response was also measured to understand the behavior at resonances of the 1^st and 2^nd bending modes as well as the effect of additional weight.

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  This paper describes the fundamental characteristics of a new magnetic oscillation direct current/alternating current (dc-ac) power converter that had fast recovery diodes added to it. The converter is constructed with a non-linear magnetic core and power MOSFETs. An ac-voltage source such as that for line electric power is connected in series to an excitation winding of the magnetic circuit. The converter can supply electric power to the ac-voltage source, and its output electric power can be controlled with a small signal current that flows through the control winding. The waveform for the output current of the converter is almost sinusoidal. The output electric power of the converter was increased by adding the fast recovery diodes outside the MOSFETs to cancel and replace the body-diodes of the MOSFETs.

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  Various circular high-energy accelerators designed on the synchrotron concept have recently been operated in order to provide high-intensity beams for the studies in fundamental physics, and those for medical purposes, and to drive reactors. The method of fast injection/ejection method by using pulsed magnets is the most fundamental techniques required in such high-energy accelerators. A kicker magnet system is often used in this method, where the magnetic field is a trapezoid with a fast rise-time of less than 1 μs and only has a long flattop for short periods of beam injection/ejection. Those should be zero for almost the entire period except for beam injection and ejection. The operation point of magnetic materials has conventionally been designed at very low fields to prevent magnetization from producing a zero field. Operation over the saturation point of magnetic materials was conducted in this study, and favorable performance, which exceeds that of conventional kicker magnet systems, was obtained. The experimental results are presented in the paper.

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  This paper describes the numerical analysis of fundamental characteristics of a magnetic oscillation direct current/alternating current (dc-ac) power converter that can supply electric power to an ac-voltage source such as a line electric power source. We present a simulation model of the magnetic oscillation circuit based on a general purpose circuit simulation program called “SPICE” to quantitatively analyze it. The simulation results of the fundamental characteristics agree well with those from experiments. A method of improving the characteristics to control the output electric power, which is based on the analytical results, is also described in this paper.

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  Switched reluctance (SR) motors have a doubly salient pole structure and concentrated individual winding on each stator pole, while the rotor has no winding or magnet. Hence, SR motors have several advantages such as a simple and robust structure, low manufacturing cost, and excellent reliability under high temperature. Such advantages make SR motors suitable for the in-wheel direct drive motors used in electric vehicles (EVs). However, higher torque density is required since the volume of the motors is limited by the wheel space. We designed three kinds of axial-gap SR motors, i.e., a single stator, a double stator, and three-stator, two-rotor motors. The basic characteristics of these motors were calculated with the finite element method (FEM). As a result, we demonstrated that the axial-gap SR motor had higher torque density than a conventional radial-gap SR motor.

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  The recent importance of designing and analyzing permanent magnet (PM) motors taking into consideration magnetic nonlinearity, torque ripple due to slot harmonics, and the eddy current loss of rare-earth magnets is increasing following an increase in the power density of PM motors. In addition, both their drive circuits and controllers should be taken into account together since powerful and efficient motor drives are not achieved without current vector control. The finite element method (FEM) is widely used for designing and analyzing motors, but it is difficult to take current vector control into account. The magnetic circuit method has a simple analytical model and it is relatively accurate for calculations. Furthermore, electric-magnetic-mechanical coupled analysis can easily be carried out. We propose here a method of calculating a magnetic circuit for a PM motor with MATLAB/Simulink, and discuss a demonstration simulated using current vector control.

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  Large trailers have large displacement engines, and their effect on the environment is not negligible due to their high average fuel cost. Additional problems are poor running stability and wear of brake linings due to their large heavy body. Therefore we are developing in-wheel SR motors for large trailers. We took into consideration the effect of reducing fuel costs for large trailers by installing them with in-wheel SR motors using legal running patterns to measure the fuel costs for heavy vehicles.

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  This paper proposes a partial zero^-power controller to move a levitated body under energy-saving conditions using a magnetic levitation device that allows three-dimensional motion. Modeling was specifically performed to control the feedback of each independent x^-, y^-, and z^-direction in a controlled system. The z^-direction was controlled by using voltage integration with zero power while the x^- and y^- directions were manipulated with positioning control. After doing experiments on horizontal displacement on the three points on the x^-z plane, we verified that the levitated body smoothly shifted to its required value for the x^- and y^- directions and it moved with zero^-power input voltage toward the z^-direction.

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  Mobile devices are not sufficiently convenient yet because it is necessary to frequently charge them. This is especially inconvenient when their battery power has slightly discharged. We have researched a contactless power transmission system (CLPS) to enable charging between mobile devices. We propose a charging system at a station because many types of mobile devices can be installed there. We tested a charging system between mobile devices and a station charging system using the same coil within mobile devices and confirmed that the systems were extremely effective and provided steady transmission of electrical power.

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  The technology to transfer power wirelessly in a variety of fields has attracted people's attention recently because it increases the convenience of many devices. There are many methods of wireless power transfer including microwaves, magnetic resonance, electric resonance, and electromagnetic induction. The method we applied is that of electromagnetic induction. We can more easily supply devices with large reserves of power by means of this method than with other techniques of power transfer. We discuss here the relationship between efficiency and the figure-of-merit in a secondary-side resonance circuit and propose a matching technique to achieve maximum efficiency.

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  We previously proposed a technique to analyze a planar parametric transformer using the harmonic balance method. The calculated characteristics of the transformer agreed approximately with the experimental ones. We analyze here the characteristics of two-degree-of-freedom parametric oscillation to confirm the validity of analysis of a parametric oscillation using the harmonic balance method. The characteristics of the relation between the input and output voltages and the phase of the two-degree-of-freedom parametric oscillation device were obtained using thismethod.

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  To shield environmental magnetic noise, magnetically shielded rooms (MSRs) made of ferromagnetic materials are used for biomagnetic measurements. The shielding performances of MSRs are usually represented by the shielding factor, SF. The source of environmental noise is far away from the MSR, so that almost uniform magnetic field is applied to the MSR. Therefore, the shielding factor SF₀ for uniform magnetic field needs to be evaluated. To evaluate SF at a construction site, magnetic noise is applied to the MSR by coils. However, the magnetic noise generated by coils is not uniform, and SFs depend on the sizes and positions of the coils and are not unique for the same MSR. Therefore, standardization of a method to evaluate SF₀ accurately using coils is being discussed by the Japan Electronics and Information Technology Industries Association (JEITA). We discuss here a method for estimating the SF₀s of MSRs by placing a smaller coil near the MSR under the condition with very low frequency, in which the eddy current effect can be neglected, using both 3D linear and nonlinear magnetostatic field analyses and measurements. A method to estimate SF₀s by extrapolation using simple numerical expressions representing the relation between the SF and the size and the position of the coil is proposed in the 3D linear magnetostatic analysis. The proposed method is applied to an experiment with a single-layered MSR under ideal conditions. Namely, MSR is placed in a spacious building so that the experiment is not affected by the steel frames and the reinforcing bars of the building. Moreover, the door of MSR does not affect its SFs. In these conditions, we were able to accurately estimate SF₀s in the experiment.

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  Functional electrical stimulation (FES) is the therapy used in the rehabilitation of lost movement functions, and to apply stimulation, the implanted direct feeding method was adapted. In this method, stimulus energy and signals for controlling devices are applied to the devices by a mounted system using magnetic coupling. In a previous study, the mounted coil was developed to be able to generate the magnetic flux for supplying energy and communication with the time-division exciting method. However, this exciting method reduces the communication speed to half of the specified speed of the mounted communication coil. In addition, the previous driving method requires an equal number of inverters as communication coils, which consumes a lot of energy. To address these problems, a new driving and exciting method have been proposed, in which the communication speed is not reduced and it needs a single inverter to excite coils. In this report, these new methods are introduced, and the experimental results show that the possibility of the whole area communication for the direct feeding method and the single source driving method.

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  In this paper, we introduce a biologically inspired walking robot and its biomimetic mechanism. The proposed magnetic robot is driven by a rotating magnetic field. The magnetic musculoskeletal structure (MMS) of the actuator produces magnetic torque within the rotating magnetic field. In addition, the rotating magnetic field provides wireless and battery-free operation to the micro-robot. The musculoskeletal structure of the human shoulder is developed by magnetic artificial muscles that consist of an NdFeB ball-type permanent magnet, 25 um polyimide thin film, and a metallic ring. Using the proposed system, we realized a new walking mechanism and walking robot for magnetic micro-robotics. The walking pattern depends on the direction of the magnetic torque between magnetic moment on the ball magnet and the rotating magnetic field. The direction of the magnetic moment is fixed. Therefore, the plane of the rotating magnetic field and the rotating direction are changed by an external joystick. This control method provides various walking performance such as turning, forward, and backward capabilities. The developed walking robot is analyzed through magnetics, biomechanics, and robotics. These various approaches can contribute development of the magnetic robotics.

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  The needle type probe consists of four spin valve giant magnetoresistive (SV-GMR) elements connected in a Wheatstone bridge. SV-GMR sensing element has dimmensions 40 μm per 75 μm. Needle probe has sensitivity equal to 11μV/μT. Extremely small size and specific construction of this type probe make it possible to detect the changes of susceptibility directly from the sample. The aim is to present the methodology for spectroscopy measurements by SV-GMR needle probe. This article introduces setup feasible to perform spectroscopic magnetic markers measurement. It includes preliminary data connected with signal changes caused by magnetic markers dilution. It shows influence of particle size changes (120 nm, 3.5 μm, 6.5 μm) on real and imaginary part of complex susceptibility. While performing measurements probe sensing elements were placed inside the sample. The intension of this work is to address the methodology for spectroscopy measurement which can be applied in liquid phase immunoassay in the future.

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