Changes in the crystal structure, magnetic properties, and electrical resistivity of Fe-Co-Ni+ (4-8) at% V alloy ribbons were investigated. It was found that the fcc-bcc phase boundary in the ribbons with 8 at% V shifted toward the Fe-rich composition side by about 10% from the position for the ribbons with no V. The coercivity and saturation magnetization decreased drastically when the crystal structure changed to the fcc structure with the addition of V to the bcc Fe-Co-Ni composition. The magnetostriction of the fcc structure was smaller than that of bcc samples. The electrical resistivity increased with the addition of V.

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The structure and magnetic properties of melt-spun multicomponent Fe₇₂Ga₂Al₅P_11-xC₆B₄Si_x (x=0, 1) with thicknesses from 20 to 440 μm were investigated. The addition of 1 at% Si instead of P to Fe-Ga-Al-P-C-B glassy alloy was found to be effective for extending the critical thickness to maintain a single amorphous phase (t_max) and a supercooled liquid region (ΔT_x). The values of t_max and ΔT_X are 140 μm and 51 K for Fe₇₂Ga₂Al₅P₁₁C₆B₄ and 160 μm and 58 K for Fe₇₂Ga₂Al₅P₁₀C₆B₄Si₁. The soft magnetic properties of the Fe-based glassy alloy containing 1 at%Si are comparable to those of Fe₇₈Si₉B₁₃ amorphous ribbon with a thickness of under 70 μm, and better than those of the same ribbon with a thickness of over 70 μm. It is therefore expected that the Fe-based glassy alloy containing 1 at%Si will be widely used as a bulky amorphous material with good soft magnetic properties.

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Amorphous Fe₇₅Si_12.5B_12.5 powders were fabricated by spinning water atomization process (SWAP). The powders obtained exhibited good soft-magnetic properties up to particle size of about 200-300 μm. These amorphous particles were insulated by glass powder and pressed into toroidal and E shape cores by hot-pressing techniques at relatively high temperature conditions below crystallization temperature. The densities of the pressed cores were about 80-85%. The magnetic properties of toroidal samples 20 mm in diameter were measured after annealing. For the core pressed at 1.5 GPa, 465°C, the core loss at 100 kHz was 13 J/m³ = ( = 1.3 W/cc) for B_m = 0.1 T and the initial permeability was about 100 in the frequency range up to 1 MHz for H_m = 5 mOe, which were comparable to those of commercial Sendust compressed corse and Fe-based gapped amorphous ribbon cores for application to fly-back transformers or choking coils operating at frequencies above 100 kHz.

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The resistivity of polycrystalline MgZn-ferrites (Mg_1.8-xZn_0.2Fe_1+xO₄, 0.79≤x≤1.23) was measured in the temperature range 293-393 K. It showed a maximum value near the stoichiometric composition. Analysis by complex impedance spectroscopy indicated that a potential barrier exists at the grain boundary in stoichiometric composition. According to TEM analysis, the silica concentration at the grain boundaries was higher than the silica concentration of grains. Actually, the resistance at the grain boundaries is one of order magnitude higher than the resistance of grains. This result supports the findings of both complex impedance spectroscopy analysis and TEM.

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To investigate the iron loss of MnZn ferrites, we simulated the frequency characteristics of the hysteresis loss P_h and eddy current loss P_e in a toroidal core by using the spatial network method. Hysteresis and conductivity were considered in the model of an MnZn ferrite, to compute their mutual influence. The results show that both losses are considerably influenced by the skin effect at high frequencies (over about 200 kHz), and that the ratio of hysteresis loss P_h to iron loss increases with an increase in the magnetic field intensity, because of nonlinear phenomena caused by hysteresis of the core.

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In single crystals of yttrium iron garnet irradiated with white light at 77 K, a remarkable change was observed in the temperature dependence of complex permeabilities μ' and μ". Simultaneously, conspicuous double peaks of DA around 125 K (DA1) and 200 K (DA2) were found to be induced by the irradiation at 77 K, with correlative onset of an irreversible decrease of permeability at low temperature. Besides, the dark DA (DA3) independent of white-light irradiation was observed around the room temperature. The activation energy of DA (1, 2, 3) may be calculated as 0.46, 0.60, and 0.88 eV, respectively.

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In this paper, we propose a new method for estimating the position and inclination angle of a reverse-side crack in a steel plate. To detect a crack existing on a side of steel plate opposite to a sensor, we have devoloped a new rotational magnetic flux sensor with a three-axis search coil centered between two pairs of exciting coils. It can measure the magnitude and phase of the magnetic flux caused by a crack in a steel plate. Using steel plates with a crack machined in the center, we investigated the relationship between the position and inclination angle of the crack and the output signals obtained by the three-axis search coil. The experimental results show that the sensor can detect the position and inclination angle of the reverse-side crack clearly.

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We developed highly accurate optical magnetic field sensor probes. New probe-type sensors 5 mm in width were designed, using a confocal optical system with two drum-shaped ball lenses. BiRIG films were prepared by the LPE method. We found a new garnet composition, Bi_0.98Gd_0.92La_0.03Y_1.07Fe_4.72Ga_0.28O₁₂, that showed high temperature stability for sensitivities less than 2.0% from - 20°C to +80°C. The linearity error of the sensor output was obtained within 1.0% for alternating magnetic fields from 5.0 Oe to 450 Oe. We also developed optical current transformers (OCTs), using this sensor and a permalloy magnetic core with a 6 mm air gap. The sensitivity of the new OCTs is about four times higher than that of our previous ones. The OCTs showed high performance in practical use.

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Sensors used in the medical field require biological compatibility and low electricity. This paper proposes a new differential position sensor with amorphous wires in a silicon membrane (A-S sensor). A sensor was manufactured and its characteristics were evaluated. The results may be summarized as follows:
1. The ac permeability of the amorphous wires was in the range from 830 to 21,000 for frequencies from 1 kHz to 100 kHz. It is recognized that the amorphous wires were made of high-permeability material.
2. To satisfy the conditions of reduced electricity and increased sensitivity, the frequency chosen must be in the range from 46 kHz to 74 kHz.
3. The detective sensitivity of the A-S sensor was shown by using the following appr oximate expression:
V_out=26.4x [V]
The A-S sensor has a potential application in monitoring a patient‘s heart beat to prevent sudden death.

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This paper presents new micromagnetic sensors with high sensitivity and stability and low power consumption using an amorphous wire MI head and a C-MOS inverter IC. The sensors employ the pulse response MI effect. The basic properties of the pulse response MI effect in amorphous wire ( (Fe_0.06Co_0.94)_72.5Si_12.5B₁₅) and two kind of sensor circuits are reported. The impedance in the MI head is sensitively changed to more than 80%/Oe owing to a sharp current magnetization. The sensor circuits operate with a high stability because of a current-source-like operation in the C-MOS IC, and the independence of the field detection sensitivity with respect to the oscillation frequency of the multivibrator. The power consumption in the sensor circuit is less than 0.5 mW.

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The magneto-impedance (MI) effect was observed in a sputtered FeCoB thin film of 1.7 μm thickness, 1 mm length, and 10 μm width when a very sharp pulse current was applied to the film. A CMOS multivibrator was used to obtain a sharp pulse. The pulse width at half the magnitude of the pulse applied to the film was around 2.5 ns, voltage change ratios of - 1 mV/Oe and 120 mV/Oe were obtained in films annealed in transverse dc fields of 60-70 Oe and 100 Oe, respectively. The conditions for generation of the skin effect were analyzed with respect to the pulse shape, pulse frequency, and critical sinusoidal wave frequency.

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This paper describes an eddy-current-type target-detecting sensor with a short-circuit plate in a railway maintenance car. The output voltage of the detecting coil is disturbed by the vibrating displacement of the measuring frame, which is located near the detecting coil. The disturbed voltage of the detecting coil is decreased 1/10 by the short-circuit plate, which is located between the detecting coil and the measuring frame. The influence of the loop and the separate-type short-circuit plates on the output voltage of the detecting coil was investigated. The results show that the separate-type short-circuit plate has twice the output voltage of a loop-type plate.

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Electromagnetic tachometers (EMTs) are used with products from many different industries. Evaluation of their performance requires magnetic field analysis. We simulated the electromotive force (emf) dependence on the yoke in circular cone shape and the thickness of the cylindrical permanent magnet, using the simpler emf calculation method with the finite element method. As a result, the value of emf/ (coil turns) in this simulation was 380% of that for the current yoke shape. Next, we compared the emf of an Al-Ni-Co magnet with that of a Sm-Co magnet. For the current magnet thickness (12 mm), the emf values of the magnets were close. For smaller magnet thicknesses, (3-9 mm), however the emf of the Sm-Co magnet was higher than that of the Al-Ni-Co magnet Therefore, EMTs can be made smaller and with higher emf than current models.

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This paper reports the performance of a LC resonant magnetic thin-film sensor. The impedance of the sensor changes according to the magnetic field dependence of the permeability and LC resonance of the sensor at high frequencies. To obtain high sensitivity, the conductor layer was covered with insulating layers and magnetic layers. As a result, a large impedance change of 105% was achieved.

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A method of imaging the permeability and anisotropic permeability on the surfaces of steel shafts is presented. This kind of method is important in evaluating steel shafts used for magnetostrictive torque sensors. We have developed a magnetic probe that can detect the average permeability and anisotropic permeability at the same time. The probe has primary coil and two sets of secondary coils for measuring the permeability and magnetic anisotropy, respectively. We found that the average permeability had a clear helical pattern, possibly introduced during the final process of manufacturing, in which rollers are used to make the steel bars straight. We also observed anisotropic permeability patterns induced on a shaft excited by the pickup head of a torque sensor. The relationship between the zero-level fluctuation of the torque sensor and the anisotropic permeability pattern is shown.

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Equipment used in the high-frequency band can accomplish thin styling, miniaturization, and being an integrated circuit according to the rise of the frequency band used. Electrical circuit wiring and parts are often close to a generation source of GHz-range frequencies and a high-frequency central processing unit, and are exposed to high-frequency noise.
The purpose of this investigation is to create a monolithic noise suppression device that decreases the frequency noise in the GHz range by means of a soft magnetic thin-film core. A monolithic 3-step LC low-pass filter was constructed from a thin-film helical inductor and a thin-film MIM (metal/insulator/metal) capacitor, and obtained high attenuation characteristics of - 50 dB at 1.25 GHz and band attenuation characteristics with a width of about 1 GHz.
Moreover, magnetic loss simulation suggests that effective resistivity of the CoFeSiB/SiO₂ multilayered film used as a film inductor is approximately 500 μΩcm.

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To achieve stable torque control, rotor information on squirrel-cage induction motors was obtained for the first time by using highly sensitive magneto-impedance micromagnetic sensor. The magnetic field detected near the edge of the rotor shaft was estimated to be proportional to the rotor current with a slip frequency (psf/2) and a torque when the motor was driven with a constant V/f inverter. Stable control of the stationary torque was realized independently of the motor temperature variation.

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A buck-converter using a multilayered micro-inductor with Fe (Co-Fe)-Hf-O-based soft magnetic films was investigated. Fe (Co-Fe)-Hf-O films have excellent frequency characteristics with a low loss factor in a frequency range exceeding 100 MHz owing to their high electrical resistivity. Consequently, a micro-inductor using these films exhibited maximum values of the quality factor (Q) of 12.0 at 5 MHz and 17.1 at 10 MHz for Fe-Hf-O and Co-Fe-Hf-O films, respectively. The highest output power, 1 W, and the highest efficiency, 70%, were simultaneously obtained for a buck-converter with Co-Fe-Hf-O films. These values are higher than those for a 1 MHz-driven converter using a Co-Ta-Hf amorphous alloy film. As the operation of the converter depends more strongly on the equivalent resistance (R) and Q values than the inductance (L), a Fe (Co-Fe)-Hf-O film reactor with a very small value of R is suitable for a micro dc-dc converter with higher switching.

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This paper describes the transient characteristics of an orthogonal-core type push-pull parametric transformer. We analyzed the characteristics by means of a circuit network, in which the reluctance network of an orthogonal-core and the outer electric circuits are coupled with each other. As one example of the transient analysis, we calculated the voltages and currents of the transformer when a short-circuit fault or an open circuit occurred in the load circuit. Some useful information for the design of the transformer was obtained.

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Current-feedback magnetic multivibrators are widely used as power sources for electronic equipment, because they are highly efficient and reliable. However, these circuits have no ability to protect themselves from overloading, and the oscillation frequency changes according to the load current. In this paper, we propose a new current-feed-back multivibrator with overload protection and frequency compensation. In addition, the condition for cessation of oscillation and that for fixed frequency of oscillation are derived by analysis. These conditions can be determined independently of each other.

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The electromagnetic pump (EMP) was developed to overcome the capacity and efficiency limitations of previous machines. This paper proposes a flux-concentration-type electromagnetic pump using that the flux-concentration effect, which depends on eddy currents, and discusses the calculated and experimental dynamic characteristics of an in-sodium tests system. According to the experimental results, the maximum flow rate was 520 l/m and the efficiency was over 10%. The calculated results estimate that the pressure of the new EMP is 1.7 times more than that of a conventional one. A new configuration of the EMP is proposed to increase the capacity of the flow rate, and its dynamic characteristics are discussed.

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Cross coils that operate in an alternating magnetic field are proposed for transmitting signals. They cancel the noise induced by a symmetric magnetic field stem from a transcutaneous power-transmitting coil, and then transmit and detect the signals in the magnetic field. In comparison with figure-of-eight coils, cross coils keep a certain sensitivity due to dislocation between the transmitting and detecting coils. The signal-transmitting ability of cross coils is not very high, but above properties make them useful as transcutaneous signal-transmitting coils.

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A new method of contactless energy transmission to moving loads such as electric vehicles (EVs) is proposed. Employing rectangular and spiral coils for the primary and secondary windings in our cordless power station (CLPS), we transmitted over 200 W of energy to an EV motor. The rectangular coil was used for stable transmission in the event of coil misalignment, and the spiral coil for efficient reception of flux from the primary coils. By placing many rectangular coils with their longer sides aligned with the EVs direction of motion, we caused that the energy transmitted was more or less stable with respect to displacement of the EV. A switched excitation system that we added to the primary coils enhanced the total transmission efficiency. A noteworthy feature of the system is that it is controlled by human intention. Only one coil is excited, to the one nearest to the load, to improve the overall efficiency.

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This paper presents the local magnetic properties measured in a three-phase induction motor model core. The relationship between the magnetic field strength vector H and the magnetic flux density vector B was obtained by measurements with a special sensor using the H-coil method and the double-needle method. As a result, the relationship between the H-vector and the B-vector was clarified, and it is shown that the local properties in an actual core are vectorial in nature.

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The magnetic properties of silicon steel sheets with a bias field are described. In the analysis, the magnetization characteristics under a sinusoidal-flux condition are approximated by the Fourier series, and it is assumed that the eddy current factor is proportional to the rate of change of the flux. The magnetization characteristics with a bias field are modeled by three magnetization curves under a sinusoidal-flux condition with a different maximum flux density. The iron loss, maximum value and harmonic component of exciting current are obtained by the numerical analysis of the relation between the dc current. The results of the analysis were confirmed by experiments, and are used to show the magnetic properties of a power transformer with a bias field using magnetic properties under a sinusoidal-flux condition.

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The rotational iron loss, W_R (B_L B_C), of electrical steel sheets at two-dimensional flux densities B_L and B_C were compared with the sum of the alternating iron losses W_L (B_L) and W_C (B_C) at B_L and B_C, respectively. In the case of B_L+B_C<2T, K nearly equals l, where K is the ratio of W_R (B_L, B_C) to W_L (B_L)+ W_C (B_C). For B_L+B_C>2 T, K<1, the value of K is almost independent of the grade of a non-oriented steel sheet. K is higher in a grain-oriented steel sheet than in a non-oriented steel sheet, and is highest in a doubly grain-oriented steel sheet. The rotational iron losses can be approximately estimated from the alternating iron losses and the constant K. In a non-oriented steel sheet, which is polycrystalline, if B_L+B_C is low, it is assumed that each crystal grain is mainly magnetized along the easy axis, even if the exciting field is rotational, and that the rotational iron loss is almost equal to the sum of the alternating iron losses in two directions.

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To measure the properties of a specimen with a conventional two-dimensional magnetic measurement apparatus, it is necessary to make a rectangular sample sheet by cutting off the superfluous parts so that place the materials can be placed in a space formed by yokes, simplified apparatus that can be applied to any sample size is needed for use in the manufacturing process of magnetic materials. This paper presents as simplified measurement system and describes its basic characteristics.

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This paper presents the method for calculating the external self-inductance L_e, the internal self-inductance L_i and the mutual inductance M of a conductor in LSI packages, and the estimation of those methods.
A straight conductor with a cross-section of 5 × 60 μm is divided into between 48 and 19,200 straight segments. The inductances L_e, L_i, and M can be calculated by the electrical formulas, since all segments are in parallel. The accuracy of the calculation is about 0.2% at L_e when the conductor is divided into 300 segments, and about 5.5% at L_i when the conductor is divided into 19,200 segments.
L_i is decreased from 132 to 36 pH by the skin effect when the frequency is increased from 0.1 to 1.9 GHz.
The inductance L, of a specimen with a micro-strip line is calculated and measured. The difference between the calculated and measured values is less than 17% in the frequency range from 1 to 10 MHz.

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In neuromagnetism research, it is important to accurately estimate internal electrical sources in the human brain from the spatial and temporal distributions of magnetoencephalogram (MEG) measurements on the surface of the head. In this study, we compared the performance of distributed internal source estimation in the human brain under two different MEG measurement conditions: (a) measurements of only the normal components of the external magnetic fields and (b) three-dimensional vector measurements of the external magnetic fields. We applied the sub-optimal least-squares subspace scanning source estimation technique to both measurement conditions. The results indicated that the accuracy of the distributed source estimation could be improved by using three-dimensional vector magnetic field measurements.

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In recent years, techniques have been developed for estimating internal electrical sources in the human brain from measurements of magnetic fields (MEG). In this study, we investigate how to estimate spatially distributed sources, since this information is important for analyzing the higher functions of the human brain. We used a 64-channel whole-head-type SQUID system to record MEG activities evoked by visually cognitive tasks. Three kinds of stimuli were presented: English words, nonsense words, and random dot patterns. Spatially distributed internal sources with latencies between 320 and 420 ms were estimated by using the sub-optimal least-squares subspace scanning technique. The estimated sources were located in the frontal region for random-dot stimuli, the left temporal region for nonsense-word stimuli, and the right postero-temporal region in addition to the other regions for English-word stimuli.

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In recent years, magnetoencephalography (MEG) techniques have been developed for estimating internal electrical sources in the human brain from surface measurements of magnetic fields. In this study, we focused on speeding up distributed source estimation, using the sub-optimal least-squares subspace scanning technique with multiple scanning resolutions. As a first step, we set a coarse scanning grid over a large area of the head. On the grid points, we calculated the cost function to be used as the criterion for the existence of a source. Then, as a second step, we set a fine grid on the area with the largest cost function, and calculated the cost function again. We verified the effectiveness of this method by computer simulation, and applied it to MEG data associated with word recognition processes in the human brain. The results showed that the amount of calculation required for the source scanning could be decreased to 1/20 without decreasing the spatial resolution around the source area.

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A dental magnetic attachment is a denture retainer that, among its many advantages, includes removable connection. The sandwich-type attachment developed by the authors has an attractive force of 6 N at a height of 1.8 mm. Recently, however, dentists have expressed a strong desire for this height to be reduced. It is difficult to meet this requirement, because the attractive force of the sandwich-type structure is proportional to its height. As a solution, we devised a double-sandwich structure. FEM analysis of the magnetic circuit of the structure shows that a sufficient attractive force will be obtained at a height of only 1.0 mm. The attractive force/size performance of the magnetic circuit is roughly 35% better than that of the current sandwich-structure type.

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This paper focuses of the trial production of a pulsing magnetic field generator for magnetic stimulations of organic tissues such as brain tumor cells (RGC-6). It consists of a combination of Helmholtz coils (radius: 20 cm, height: 27.5 cm, distance between coils: 6.5 cm) to generate the magnetic field, and a flip-flop-type electric circuit to generate the pulsing electric current controlled by switching of thyristors. This generator can supply a pulsing magnetic field of 10 mT at 200 Hz with a rise-time of 0.4 ms. The uniformity of the magnetic field distribution was within a maximum error of 5.8% in the 2400 cm³ region (20×20×6cm) between the Helmholtz coils.

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We studied the transport processes of organic materials in water under intense magnetic fields using two liquid chromatographic systems to observe the transport processes of glycine, catalase, and albumin under magnetic fields of up to 8 T. We measured the rate of absorbance of glycine from an outlet of a column, using low-pressure liquid chromatography. The peak intensity in the chromatogram of glycine changed by 10-500% depending on the strength and direction of the magnetic field gradient. The retention time in the chromatogram of glycine was significantly prolonged when the direction of magnetic forces was opposite to the direction of the flow. We also measured the retention times of glycine, catalase, and albumin under magnetic fields of up to 8 T using an HPLC system. The retention times of the three solutes under gradient magnetic fields increased by 100-370%.

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This paper presents the results of computer modeling studies of the effects of a volume current with multi-sources on 3-D magnetoencephalogram (MEG) measurement. An inner-surface model (homogeneous medium: 0.5 Sm^-1) of the skull consisting of 1979 triangular elements was used. In calculation of 3-D magnetic field components (B_r, B_θ, B_φ) in a spherical coordinate system, multi-sources were set to the pariental, temporal, and occipital lobes of the brain. A 3-D second-order gradiometer developed by the authors, with an orthogonally wound Ni-Ti wire on a rectangular 3×3×6 cm solid, was also used. The base line of the detection coil for B<_r was 2.8 cm and those of the coils for B_θ and B_φ were 1.4 cm. The effects of the volume current on the tangential components (B_θ, Bφ) were not observed in the pariental, occipital, and upper parts of the temporal lobe. However, in the lower parts of the temporal lobe to the boundary, the directions of the multi-sources had some effects.

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We measured the electric fields induced by figure-of-eight coils in homogeneous and inhomogeneous volume conductor models. Each model consisted of two troughs separated by a sheet of cellophane. In the inhomogeneous model, one of the two troughs was filled with 0.9% saline solution, and the other with 0.1% saline solution. In the homogeneous model, both troughs were filled with 0.9% saline solution. The figure-of-eight coil was held beneath the troughs with its wings parallel to a boundary between the two troughs. In the inhomogeneous model, the electric field along the boundary and especially its first spatial derivative were markedly elevated in comparison with the corresponding values recorded in the homogeneous model. The response of a nerve fiber to magnetic stimulation in an inhomogeneous medium is different from that in a homogeneous medium.

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We report our observations of the corrosion pattern of a steel plate in the presence of a static magnetic field with a field gradient. The steel plate was positioned vertically in a chamber filled with purified water, and the magnetic field was applied normal to the center of the plate. It was found that the pattern of corrosion was due to both the thermal effect of the water and the magnetic field. When the magnetic field was absent, the corrosion pattern was due to the thermal convection of the water when the temperature of water was higher than that of the central part of the plate, a corrosion pattern with a pair of vortices appeared in the lower part of the plate; otherwise, it appeared in the upper part. When the magnetic field was applied while keeping the water temperature uniform, a corrosion pattern with a pair of vortices appeared bilaterally in the center of the plate. This was the first experiment to visualize the behavior of oxygen molecules dissolved in water.

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This paper describes the submersion of a glass sheet into molten metal with an electromagnetic force caused by linear induction motors (LIMs) in a glass sheet tempering process. The apparent density of the molten metal is reduced by the electromagnetic force, so a glass sheet lighter than molten metal can be sunk in it. In this process it is necessary to keep the glass sheet vertical in the center of the molten metal tank. Numerical simulations of the electromagnetic fluid flow were performed. The following condition for the glass sheet to remain stable at the center of the molten metal tank was obtained. The submersion depth of the glass sheet, that is, the distance between the surface of the molten metal and the top of the glass sheet, must be less than 5.7 [mm] if the thickness of the molten metal is 30 [mm] and that of the glass sheet 5 [mm]. In view of the character of the flow, the submersion depth of the glass sheet should be less than a quarter of the difference between the thickness of the molten metal and that of the glass sheet.

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The Moses effect and enhanced Moses effect have recently been reported, but the influence of atmospheres on the Moses effect has not been considered. In this investigation, we conducted an experiment to study this influence. A water vessel was placed in a superconducting magnet bore, and the degree of suppression in the level of water surface was observed at the field center (8 T) in nitrogen and oxygen gases. The depth of the trough was 24.7 mm in nitrogen and 29.2 mm in oxygen, respectively. The results visibly showed the influence of atmosphere on the Moses effect, and agreed with calculations according to the theory of the enhanced Moses effect.

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The magnetic field effect on the formation of a water droplet was investigated by measuring the volume of water droplets formed in a magnet with a vertical field distribution. The maximum field was 9 T at the center of the magnet bore. The droplet volume increased significantly on the upper side of the magnet with a strong field gradient and decreased at the lower side. Measurements were also carried out for several diamagnetic and paramagnetic aqueous liquids, and showed that the same effect was introduced by the presence of a magnetic force. The results agreed with those of calculation. We also succeeded in controlling the droplet volume under a magnetic field of below 1 T by forming a droplet of a liquid in another liquid of similar density.

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Eddy-current testing (ECT) is used for inspecting cracks in metal structures. We propose a planar-type ECT probe consisting of a meander and a mesh coil, and discuss the possibility of using ways of this probe to inspect disconnections in printed wirings. This paper describes (1) finding disconnections in printed wiring and (2) discriminating between various patterns of printed wiring and disconnections. Experimental results confirm that it is possible in principle to use ECT for inspecting printed wiring.

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This paper describes a new non-destructive testing instrument that searches for defects on the steel surface opposite that into which H-coil and the exciting coil are built Defects can be found with the H-coil by measuring changes in the eddy current. In this case, defects on the surface of the steel can be found according to the skin depth of the eddy current. Therefore, a moving magnetic field is effective for defects on the opposite surface of the steel, because much information is derived from the moving magnetic field in comparison with an alternative magnetic field. The shape and structure are also important to improve the sensibility of the testing instrument. In this paper, we present some results obtained with our new non-destructive testing instrument, and discuss the possibility of detecting defects in the opposite surface and subsurface region of the steel.

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In recent years, sensors have come to require high resolution and accuracy because of the progress of control technology. Magnetic encoders are widely used in servo motors in factory automation, because of their suitability for use in difficult environments. At present, the required resolution is more than 2000 pulses per revolution. The authors of this paper are aiming to create an encoder with a resolution of 4000 pulses per revolution in a drum with a diameter of 35 mm. As the resolution increases, ever greater accuracy is needed in the index phase to detect the original position of the encoder. To stabilize the index pulse, the authors took account of the width of the magneto-resistive element and the magnetization current waveform. As a result, the index pulse has been extremely steady in a magneto-resistive element with a width of 20 μm. It was found that a pulse width of less than 6.9 μm was necessary for 4000 pulses per revolution. Moreover, the usable detection gap could be expanded by magnetizing the drum in a wave form in which both sides of a rectangular wave curved inward.

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A multi-speed resolver is one of the most accurate angle sensors, which are transformers having primary rotatable windings with respect to their secondary (pick-up) windings. Multiple speeds are possible because each winding consists of a two-pole winding and a multi-pole winding. We propose a new multi-pole pick-up winding method, in which the angle accuracy is governed by the multi-pole winding, which is a sinusoidally distributed winding on a fractional slot structure (fractional winding). Through comparison of the new structure with conventional structures, the following conclusions were obtained: (1) the suggested fractional windings lead to suppression of maximum spatial harmonics; (2) surviving spatial harmonics on the winding factor involve the number of slots in the repeatable group (S_g); (3) the accuracy of the practical test results indicates that the fractional winding is superior to the conventional winding.

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Invisible bar codes such as magnetic ones play an important role in systems requiring security. The magnetic bar code system described in this paper uses magnetic anisotropy as a carrier of information. Three kinds of magnetic ink were used, containing iron base alloy, Mn-Zn ferrite powder, and carbonyl iron powder. Although the level of the output voltage needs subsequent amplification, all of these magnetic ink can be used for making magnetic bar codes, especially the one containing iron base alloy. We explain a possible mechanism for two sub-peaks occurring berfore and after the main peak.

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This paper reports an analysis of the high-frequency impedance of micromachined soft-magnetic thin films. The impedance changes according to the directions of the easy axis orientation and the dc magnetic field to be sensed. Investigation of CoZrNb films clarified that the change in permeability with the applied dc magnetic field can be explained by the bias susceptibility theory. Moreover, the change in the impedance of micromachined films can be estimated quantitatively on the basis of the dc field dependence of the permeability.

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A new method of obtaining the asymmetrical magneto-impedance (MI) effect in a zero-magnetostrictive FeCoSiB amorphous wire is presented, where in a wire coil is used to apply a wire pulse current. The mechanism for the generation of the asymmetrical MI effect is qualitatively explained by means of a magnetization rotation model for the surface layer of a wire with a spiral magnetization. A linear magnetic-field sensor circuit uses the amorphous-wire asymmetrical MI element magnetized with a sharp pulse train current in a C-MOS multivibrator circuit.

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The paper presents a morphological study of real-time magnetocardiograms (MCGs) of a normal subject. The MCGs were measured by using a 3-D second-order gradiometer connected to three rf-SQUIDs in a prefabricated magnetically shielded room. The base line of the detecting coil for B_z is 2.8 cm and that of the coil for B_x and B_y is 1.4 cm. The magnetic field components perpendicular to the chest (B_z component) and tangential to the chest (B_x, B_y components) were studied. From isofleld contour maps and arrow maps of the QRS wave of the MCG, when multiple sources exist simultaneously, we can infer the locations and positions of different sources by combining the B_z component with the B_x and B_y components. The analyzed results showed that a method using of a 3-D second-order gradiometer that we developed is useful for discriminating the directions and locations of multiple sources.

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This study focuses on a 3-D measurement of magnetocardiograms (MCGs) of a subject with myocardial infarction (MI). We carried out the measurements in a prefabricated magnetically shielded room, using a 3-D second-order gradiometer connected to three rf-SQUIDs, which can detect the magnetic field component perpendicular to the chest (B_z) and tangential to the chest (B_x, B_y). In this study, fast Fourier transform (FFT) was used to compare the frequency characteristics of MCGs of the MI patient with those of patients who had normal MCGs. Results showed that frequencies of less than 1 Hz dominated in MCGs (B_z, B_x) of the MI patient, compared with frequencies of 1 Hz in MCGs of patients who had normal MCGs.

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We have developed a multi-channel high-resolution SQUID magnetometer. This system consists of 12-channel pick-up coils 5 mm in diameter located on a 7.5 mm grid. The base-line of the gradiometer is 15 mm. The distance between the pick-up coil and the outside surface of the dewar is 5 mm. We measured the magnetic field produced by the activity of the orbicular muscle of eye, the magnetocardiogram produced by a human, and the magnetocardiogram produced by a rat. It is possible to obtain signals with good spatial resolution.

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