This paper proposes a new sensing method that can measure three-dimensional position inside a living body, using a magnetic field. This method is applicable to medical capsule devices, such as the capsule endoscope. The mutual induction phenomenon is used for position measurement. In order to hold constant the induced electromotive force that occurs in the secondary coil, we apply feedback control to the alternating current flowing into the primary coil. This method enables stable measurement of sensor position, even if the sensor exists relatively far from the primary coils. The position of the sensor is measured by calculating six formulas using Newton’s method. The relationship between the induced electromotive force and the theoretical value of the magnetic field is determined in advance. Sensor in vitro accuracy was verified. For distances of less than 300 mm from the sensor to the magnetic field generator, the distance error was less than 7 mm. Although a wireless sensor would be ideal, the present sensor is connected to the computer through a thin cable. Development of wireless sensor should be the next research subject.

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The experiment was carried out to investigate the effect of changing mole ratio, n (= Fe³⁺/Co²⁺), and pH conditions on magnetic and physical properties of Co ferrite prepared by the chemical coprecipitation method without post-annealing. The chemical coprecipitation compositions were chosen according to the formula (CoO)·n/2(Fe₂O₃), where n varied between 2.0 and 3.5. Optimum magnetic properties were achieved with materials of composition (CoO)·1.375(Fe₂O₃). The typical magnetic and physical properties are saturation magnetization σ_s = 61.6×10^-6 Wb·m/kg (49.0 emu/g), coercivity H_cJ = 255 kA/m (3.21 kOe), lattice constant a = 0.8391 nm, and average particle size D = 23 nm, anisotropy constant K₁ = +2.7×10⁴ J/m³ (+2.7×10⁵ erg/cm³), K₂ = −13.0×10⁴ J/m³ (−13.0×10⁵ erg/cm³), anisotropy field H_A nearly equals 3 MA/m (37.7 kOe). The rotational hysteresis integral Rh, which is related to the magnetization mechanism of these fine particles, is 1.32, and it was found that the magnetization mechanism is an incoherent one.

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I have earlier proposed a new microactuator that operates on the resonance energy of a system excited by electromagnetic force, which can move at high speed in the vertical direction. It was possible for that actuator to move only one direction, however. In this paper, a new actuator that can perform reversible motion is proposed. Shape memory alloy and a coil spring are used for change in the direction of motion. The sizes of the prototype actuators were 8 mm and 4 mm in diameter. In the experiment, the new actuator showed the same high propulsion characteristics as shown in the previous work. This actuator has many possible applications for small pipe inspections, repair, and long-distance movement.

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This paper proposes a micromotor with a rotor rotated by the resonance energy of a vibration body doubly excited by an electromagnetic and coil. The method of connecting a coil and an electromagnetic was considered, and the relation between load torque and drive frequency of a prototype micromotor was examined experimentally. It was shown that the optimal drive frequency of a micromotor exists in each load. Experimental results show that rotational, speed of 1022 rpm was obtained with load torque of 88.2 Nm when a micromotor was driven at optimal drive frequency. The torque characteristics of the micromotor improved 200 percent compared with previous research.

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Switched reluctance motors (SRM) have various desirable features, such as simple and strong construction, high reliability, low cost, and ease of maintenance, because they have no rotor windings and no permanent magnets. These features make the SRM suitable for use in low-speed multipolar generators used in wind power generation. Such a switched reluctance generator (SRG) needs a power supply for excitation and an encoder of the principle of operation. Therefore problems, such as complication of the generating system, may arise. In this paper, we propose a tandem type SRG which is directly linked by SRG and permanent magnet generator (PMG). This is expected to simplify the system.

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We describe the detailed design of a highly sensitive magnetometer based on micro-magneto-optical Kerr effect (MOKE) magnetometry, consisting of an optical microscope combined with an ordinary MOKE set-up. The system enables microscopic MOKE hysteresis loops to be measured with a spatial resolution 10⁴ times better than that of conventional longitudinal MOKE magnetometry. The sensitivity of the system is demonstrated by measuring MOKE hysteresis curves of submicron permalloy rectangular dots and wires.

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A change in the magnetic domain structure of a high- frequency carrier-type (HFC-type) thin-film magnetic field sensor (or giant magnetoimpedance, GMI, sensor) with inclined ladder-line magnetic domain walls was investigated as a function of an external magnetic field. The GMI property of the same sensor element was also investigated. Comparison of these data leads to the following results: The application of an external magnetic field causes a drastic change in the domain structure, from an inclined ladder-line to a single domain on a threshold magnetic field. The threshold field is different for increasing and decreasing magnetic fields. This hysteretic phenomenon is in accord with the hysteresis of the GMI property. It was investigated theoretically by using the bias susceptibility model of a single-domain magnetic thin-film with uniaxial anisotropy. This theoretical model predicts that contiguous inclined ladder-line domains on a 180° wall will have different values for the high-frequency permeability. An approximate estimate of the total sensor impedance obtained by adding the impedances of all the ladder-line domains shows that the hysteresis of the domain leads to the hysteresis of the GMI property. It also explains why inclined ladder-line HFC-type sensors have high sensor gain.

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A high-frequency carrier-type (HFC-type) thin-film magnetic field sensor (or giant magneto-impedance, GMI, sensor) needs a bias magnetic field of Oe order for magnetic field measurement. In this report, a thin-film magnetic bias with coplanar layout is proposed for dc bias supply. The merits of the coplanar thin-film magnetic bias are as follows. Magnetic property degradation caused by both lamination of magnetic thin-films and heat treatment is avoided. The heat treatment is indispensable for realizing uniaxial anisotropy in a Co₈₅Nb₁₂Zr₃ amorphous sensor element. Since a thin-film fabrication process is suitable for creating a coplanar pattern with precise dimensions, a precise dc bias field is obtained. An additional new structure proposed in this report uses a low-resistivity thin-film magnet for the current path of the sensor element. An SmCo₅ amorphous thin-film magnet was proposed for this structure. This conductive metal bias magnet with coplanar layout is suitable for both the return path of the carrier current, which simplifies the sensor structure, and the impedance-matching ground plane for high-frequency carriers. We confirmed the properties of these proposed structures by experiment. The temperature property and 85°C 85% RH treatment property of the sensor were also measured. The results show the effectiveness of coplanar magnetic bias in an SmCo₅ amorphous thin-film magnet.

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We investigated the effects of ZnO underlayers on the crystal orientation of L1₀ FePt polycrystalline films and found that thin ZnO underlayers with good c-axis orientation promote preferential growth of FePt (001) in spite of their different crystal lattice symmetry, resulting in excellent perpendicular magnetic properties. This unexpected result was qualitatively explained by the proposed model for lattice matching between ZnO (00·l) and FePt (001). Annealing at temperatures above 550°C, however, gives rise to chemical reactions at the FePt/ZnO and ZnO/substrate (in this case Si) interfaces, causing severe reduction of the magnetic moment of FePt and/or changes in the film morphology. Therefore, heating processes above 550°C should be avoided when we use ZnO as the underlayer material for promotion of FePt (001) orientation.

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The purpose of this study was to examine the effectiveness of active seat suspension when it is applied to small cars, and to survey the problems associated with its practical use. A small active seat suspension, which is easy to install, was designed and manufactured for one-seat electric automobiles. In a realistic driving test, a test road was prepared using hard rubber. The concavity and convexity of an actual road surface were simulated. Our aim was to develop a robust vibration-isolation system for the driver’s seat using a sliding mode control, which tolerates such factors as variation of a parameter for the driver’s weight. We performed experiments simulating several conditions, and compared the results obtained with optimal control results. The tests verified that the suppressive effect of the sliding mode control on the vibration isolation was effective.

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We investigated the effect of Zn/Te flux ratio on magnetic properties of a II-VI diluted magnetic semiconductor (DMS) Zn_1-xCr_xTe. Zn_1-xCr_xTe films were grown on GaAs(001) using a molecular beam epitaxy method and changing the Zn/Te flux ratio. In all the films, single phase of DMS Zn_1-xCr_xTe was confirmed using magnetic circular dichroism measurements. We found that ferromagnetism appears in a limited range of the Zn/Te flux ratio. The magnetic properties of DMS Zn_1-xCr_xTe depend sensitively on not only the Cr concentration but also the Zn/Te flux ratio.

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Spin-momentum transfer switching is a promising candidate for magnetization switching with quite low consumption of electricity. However, its critical current (I_c) and current density (J_c) are still too large for it to be applied to TMR films and MRAM without breaking them electrically. Decreasing the saturation magnetization (M_s) of memory cells is effective in decreasing both I_c and J_c, because they are proportional to M_s². Here we suggest the use of magnetic film with M_s of ∼600 emu/cm³ as a memory cell, resulting in the reduction of I_c by one digit. The estimated thermal durability and switching time were acceptable. The characteristic values of TMR films, which are necessary in order to apply spin-momentum transfer switching to MRAM, are now gaining practicality.

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Small, thin electric powered cellular phones are gaining remarkable popularity. The most recent cellular phones have a vibration function generated by a rotary vibration motor to notify the user of the arrival of a message.
We developed a small electrically powered linear oscillatory actuator (LOA), and investigated how it can be used to provide a new dimension to the vibration function. While it is difficult to add variety to the vibration function of a conventional rotary motor, it is easy to do so to that of an LOA.
A rotary motor can only be switched on and off, and it has a constant frequency and vibration. With an LOA, however, it is possible to adjust the intensity of the vibration by controlling the frequency. Therefore, it is possible to use various vibration patterns.
The effect of the magnetic coercive force on the magnetic spring constant was also examined.

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A hybrid thin-film coplanar transmission line with a CoFeB metallic magnetic film was fabricated and studied. The fabricated devices consisted of top and bottom 3-μm-thick aluminum conductor layers and an inner (0.5-μm-thick polyimide)/(0.5-μm- thick CoFeB)/(0.5-μm-thick polyimide) trilayer. The top conductor layer consisted of a signal line and ground planes on the same plane. The CoFeB metallic magnetic film, exposed to the same thermal process as for the device fabrication, had a static relative permeability of about 180 and an FMR frequency of about 3.7 GHz. The polyimide had a relative permittivity of about 3.5.
As a result, the wavelength shortening ratio of the fabricated device was about 0.19 at a frequency of a few gigahertz. The line length and the insertion loss of a quarter-wavelength device were estimated to be about 7 mm and about 2.9 dB at 2 GHz.

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It is known that a Co/Rh multiplayers system show strong interlayer exchange coupling and perpendicular magnetic anisotropy. In this study, we fabricated two series of Co/Rh(111) multilayers: one with a wedge-shaped Rh layer and a Co layer of constant thickness, and the other with Rh layers constant thickness and wedge-shaped Co layers. The former were used for investigation of the interlayer coupling and the latter for investigation of magnetic perpendicular anisotropy. For the Rh wedged multilayers, spin flip was observed in the M-H curve, indicating the coexistence of anti-ferro magnetic coupling and perpendicular anisotropy. The Co wedged multilayers exhibited the perpendicular magnetic anisotropy for Co layer thicknesses less than 12 Å. From the Co layer thickness dependence of the magnetic perpendicular anisotropy, we found that the perpendicular anisotropy of Co/Rh (111) can be dominated by the strain produced by lattice mismatch.

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A scanning Hall probe microscope (SHPM) with high resolution of the magnetic field was developed. The non-magnetic scanning stage allows the sample position to be perfectly controlled even in magnetic fields up to 15 kOe. The stray field distribution at the surface of ferromagnetic SmCo₅ was investigated in various external magnetic fields. The observed stray-field images show domain transitions corresponding to the magnetic reversal process.

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Co₂CrAl (x = 0) films were found to form a B2 structure, and when Fe was substituted for Cr (x = 0.4−0.6), the films crystallized B2+A2 structures, while an A2 structure was stable in the case of Co₂FeAl (x = 1) films deposited on thermally oxidized Si substrates at room temperature. The magnetic moments of the films containing Fe tended to increase with increasing x, while those of the films containing Cr were far from the values calculated with an assumption of the L2₁ structure ordering.
Spin-valve-type tunneling junctions with a Co₂(Cr_1-xFe_x) Al film were also fabricated, which demonstrated large tunneling magnetoresistance of 19.1% (x= 0.4) at room temperature and 27.2% at 5 K in spite of atomic site disorder.

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Reactive Ion Etching (RIE) is the most promising technique to realize sub-micron patterns of tunneling magneto-resistance (TMR) junctions for Magnetic Random Access Memory (MRAM) devices. However, it is difficult to be applied into practical use due to re-deposition of the etched material and corrosion by etching gases. In order to eliminate these drawbacks, an etching process utilizing CO + NH₃ gas chemistry and Ta metal mask has been applied. Electron microscopy observations confirmed that there is no re-deposition or corrosion occurs. Using the same process we have succeeded in fabricating a high-quality TMR device that show magneto-resistance (MR) ratio of more than 60 %.

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