The high-frequency magnetic properties of low-temperature deposited Co-Sm films with amorphous-like structures were investigated for application to RF micromagnetic devices; the magnetic films in such devices require superior soft magnetic properties with high ferromagnetic resonance (FMR) frequency and tolerable thermal stability for the device fabrication processes. We observed that the anisotropy magnetic field, H_k, of a Co-Sm amorphous film increases with the Sm content; the H_k was greater than 5000 Oe for an Sm content greater than 15 at.%. The relationship between frequency and permeability yielded a high value for FMR frequency due to the large H_k. The FMR frequency could be controlled by changing the Sm content and was calculated to be greater than 20 GHz by using the measured saturation magnetization, M_s, and H_k. The H_k of as-deposited Co-Sm films decreased to a value half that of film annealed at 350°C. However, the extent of thermal degradation was relatively small, thereby exhibiting a distinct uniaxial magnetic anisotropy with a sufficiently high H_k even after a post-thermal process; this made the Co-Sm films suitable for applications in the GHz band.

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This paper proposes a novel tactile sensor using magnetic suspension that consequently working between permanent magnet and magnetic material. The objective of this research is to detect shear force for the application of robotic fingertips. We proposed a freely supportive simple structure which consist of Ni-Fe pole and permanent magnet plate. The operation principle was studied by finite element method (FEM) and ±40° of optimal operation range is obtained. In this range, the movement of magnetic field core also being inspected and promising the realization of proposed idea.

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The size, shape and composition of magnetic nanoparticles make it an attractive tool in medical applications. Low concentration Dextran Magnetite (DM)® or magnetic fluid is widely used for biomedical applications. This paper reports experimental apparatus designed for testing low concentration magnetic fluid, results obtained by experimentation utilizing a simple, novel and low invasive needle-type spin-valve giant magnetoresistance (SV-GMR) sensor and numerical analysis for comparison with the experimental results obtained. Low concentration magnetic fluid weight density is estimated by the difference between the magnetic flux density inside and outside a magnetic fluid filled cavity. The results show that the proposed technique employing the needle sensor has a good potential to be used in biomedical applications such as hyperthermia therapy in cancer treatment and targeted drug delivery, for low concentration magnetic fluid weight density measurements in-vivo.

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In this paper we present the analysis of 3D measurements of the magnetocardiogram by means of current source reconstruction. The data considered are rest and exercise stress data of test subjects. The source model used to describe the heart activation is a distributed source model, which allows to follow how the heart activation spreads over the myocardium. We developed a four compartments human torso model including the heart cavity and two lungs. Different values of the compartment conductivities are used to study the effect of the inhomogeneities on the reconstructed sources. The comparison between rest and stress data is done by means of correlations coefficients that indicate how close the reconstructed sources are in terms of dipoles moments, since in the source model considered the dipoles positions are fixed and depend on the source space model geometry. The same analyses are repeated using the 3D magnetic data and only the normal component, to investigate the additional information given by the tangential components. The results show that the torso and heart conductivities have a stronger influence than the one of the lungs, and that the 3D data are less sensitive to the changes of the compartment conductivities.

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A micromagnetic simulator for a single-pole-type (SPT) writing head that takes into account the full interactions between the head core and the recording medium was accelerated by introducing the Fast Fourier Transform (FFT) into all the magnetostatic calculations. This enabled the head field and the recording process on a medium to be simultaneously calculated which is advantageous for designing a perpendicular magnetic recording head and medium system. If the head field strength is sufficiently large to realize saturation recording, the recording performance of the SPT head with a trailing shield was considerably improved by positioning the trailing shield, although the increase in the head's field gradient was slight. This result indicates that the head's field gradient is one of the most important factors for increasing linear recording density.

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We tried to fabricate pure Co_0.9Fe_0.1 ferromagnetic metal nano-contacts in the insulator layer of AlO_x. First, we verified the effect of natural oxidation (N.O.) and in-situ annealing process, and we clarified the formation mechanism of Co_0.9Fe_0.1-AlO_x NOL. In N.O. process, Al is migrated from Co_0.9Fe_0.1/Al mixing layer (as deposition state) and cohered on the surface by oxygen. As the result, Co_0.9Fe_0.1 path is pure. By in-situ annealing, Al near the surface migrate to the Co_0.9Fe_0.1/Al mixing surface by residual oxygen in the ultrahigh vacuum chamber, and the other Al diffuse to Co_0.9Fe_0.1 at the same time. Next, we observed the surface of Co_0.9Fe_0.1-AlO_x NOL by in-situ conductive AFM (c-AFM). We confirmed the metal paths in an area with a diameter of about 1 nm.

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In order to achieve high-density recording, the reproduced waveform needs to be improved. In this work, we clarified the correlation between the transition jitter and transition width, and tried to express the correlation. However, the correlation was not one-to-one, because of the appearance of island domains off the transition line. It was found that the islands tended to affect the increase in transition width.

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Exchange-coupled Composite (ECC) media have attracted a great deal of attention as a potential solution to the tri-lemma between the signal-to-noise (SNR), thermal fluctuations, and the writability of recording media. Several methods have been proposed to systematically design ECC media, taking into account the above-mentioned three issues. A method of evaluating the thermal stability of thin-film media, however, has not yet been established. Monte Carlo methods have been widely used to evaluate to long-term thermal decay, but their application is doubtful to strong exchange-coupled systems such as ECC media. The Langevin method is also limited to very short-term thermal decay. In this paper, we propose a simple method of evaluating thermal decay that combines an analytical method with Langevin calculations.

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The influence of the coercivity of perpendicular magnetic recording media as slave media on their perpendicular duplication characteristics was investigated by using micromagnetic simulation. It was found that even for slave media with high coercivity, the magnetic patterns are duplicated on the slave media most clearly when duplication field is much the same value as the coercivity. The duplication characteristics improve as the coercivity of the slave media increases, on account of the increase in the gradient of the recording field as the duplication field increases. The fundamental harmonic wave and the distortion of the output waveform also improve as the coercivity of the slave media increases.

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In recent extremely narrow-track recording, the recording resolution at the track edge has become a crucial issue. Slight write fringing should not be permitted in future high-areal-density recording. The erase band (EB) that is formed at track edges is previously thought to be able to suppress the crosstalk noise from adjacent tracks by trim-erasure for the off-track condition. This is an advantage. However, the erase band is a randomly magnetized area that may emit track edge noise. We calculated the erase band width (EBW) accurately by a newly proposed technique, and derived the analysis type of the 747 curve by using Lee's analysis-style derivation technique. As result, we found that the peak of the track edge noise is outside of the EB and that the EB is the outbreak source of the noise. We also confirmed that a bump in the 747 curve produces without the EB noise, and that there is close relation between the shape of the 747 curve and the EB noise.

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The feasibility of magnetic contact duplication for perpendicular magnetic recording (PMR) media at 1 Tbit/inch² was investigated by using micromagnetic simulation. The exchange constant dependence of the duplication performance has a maximum value. Two factors improve the duplication performance: decreasing the c-axis distribution of the recording layer and decreasing the distance between master and slave disks. However, the anisotropy field dispersion of the recording layer has almost no influence on the duplication performance. When the c-axis distribution is decreased, the exchange constant is optimized and the spacing is less than 5 nm, the magnetic contact duplication for PMR media at 1 Tbit/inch² is feasible.

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The dependence of the MR properties of CPP (Current Perpendicular to the Plane)-GMR (Giant Magneto-Resistive) sensors with a Co-Fe/Cu multilayer on sensing current was investigated. A CPP-GMR sensor with a [Co₉₀Fe₁₀(1.5 nm)/Cu(2.0 nm)]₁₆ multilayer had an MR ratio of 17.5 %. The MR ratio monotonically decreased with increasing sensing current. Split peaks for the MR ratio were also observed in an MR curve, when sensing current was so high as to drastically decrease the MR ratio. We calculated the MR curves with a simple coherent rotation model assuming a circular current induced field, and confirmed that the calculated MR curves were qualitatively in good agreement with experimental ones. The micromagnetic simulation for read-head dimensions also revealed degradation in the MR ratio due to the current induced field. The simulated results indicated that reducing the sensor size would effectively suppress the current induced field, which resulted in high output. The estimated output and head-amp SNR for a size of 50 x 50 nm were over 2 mV and 33 dB, respectively. Therefore, a CPP-GMR sensor with a Co-Fe/Cu multilayer possibly had sufficiently high potential to be a candidate for future recording technology.

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The influence of the inclination angle of the master pattern on the duplication characteristics during the formation of a phase servo pattern on perpendicular magnetic recording media by edge printing was investigated by using an enlarged model. The perpendicular components of both the recording field and the magnetization of the duplicated slave medium decreases as the inclination angle of the master pattern increases. The influence of the inclination angle of the master pattern on the magnetization is small in comparison with the influence on the recording field, and even for an angle of 40 degrees, edge printing on slave media is possible.

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We developed high-speed differential-susceptibility measuring equipment to examine thermal fluctuations in magnetic materials. In this study, we measured the dependence of the differential-susceptibility of a magnetic tape on a magnetic field by using the equipment. When the sweep speed of the magnetic field changed from high to low in the order of ms, the magnetic field that gave the maximum differential susceptibility shifted from a high to a low magnetic field due to thermal fluctuations. However, when the sweep speed of the magnetic field changed from high to low in the order of μs, the shift in magnetic field was not clearly detected. The time when the magnetization in the easy direction changed from the residual to the zero state obtained from a linear field, and the time obtained from the constant field, which is the same as the coercivity of the linear field, were calculated using micromagnetic simulations. From the ratio of the two times and from an experimental time when the applied field reached coercivity, a time that could be applied to Sharrock's equation was obtained. In order to fit the experimental results to Sharrock's equation, K_u must be much smaller than the experimental value and H₀ must be much smaller than H_k (H₀/H_k=0.38). Here, K_u, H_k, and H₀ are anisotropy constat, anisotropy field, and coercivity at 0K.

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Ceramic composites (x Ni_0.15Cu_0.3Zn_0.55Fe₂O₄ + (1-x) BaTiO₃) were prepared by a conventional ceramic method. X-ray diffraction (XRD) and electron probe micro analysis (EPMA) measurements were performed for these samples and it is confirmed that the composites consist of spinel ferrite and BaTiO₃ phases. The composites are so homogeneous that the ferrite and BaTiO₃ grains do not react to each other and have radii of 1-5 um. The resonant frequency in initial permeability and permittivity is increased by increasing the amount of BaTiO₃.

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This paper discusses the direction dependence of the magnetic properties of non-oriented electrical steels (NO). The direction dependences are due to magnetic anisotropy induced by grain boundaries, steel edges and manufacturing stresses. NO sheets are easy to magnetize in the rolling direction (RD), because of the RD magnetization orientation induced by grain boundaries. Therefore, NO sheets have uniaxial direction dependence at lower magnetic flux densities. However, the direction dependence at higher densities is affected by the {110} steel surface which is present to a small extent in NO, although NO has generally {111} sheet surface texture that hardly affects the direction dependences.

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The diameter and composition of magnetic crystal grains in a CoCrPt-SiO_X perpendicular magnetic recording medium were investigated by using a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray spectrometer (EDX). It has been shown that the composition of individual grains depends little on the grain diameter. The variations in the uniaxial anisotropy constant (K_u), the saturation magnetization (M_s), and the anisotropy field (H_k) are estimated from the composition for individual magnetic crystal grains. The thermal stability of magnetic crystal grains is discussed on the basis of the estimated K_uV/kT values on the assumption that the magnetic crystal grains are magnetically separated.

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The magnetization process of an Nd-Fe-B hydrogenation-disproportionation-desorption-recombination (HDDR) magnet was studied by measuring its initial recoil curves. When compared with those of Nd-Fe-B sintered, HDDR and melt-spun magnets, the behavior of the initial recoil curves of the HDDR magnet was similar to that of the sintered magnet when the applied magnetic field was relatively small. The behavior of the initial recoil curves of the HDDR magnet became similar to that of the melt-spun magnet when the applied field became larger. The magnetic microstructure of the HDDR magnet was observed by means of a magnetic force microscope (MFM). When the HDDR magnet was thermally demagnetized, the distance of two domain walls was smaller than the average grain size of the HDDR magnet. On the other hand, the distance of two domain walls was larger than the average grain size of the HDDR magnet when the magnet was magnetically demagnetized. These results suggest that the HDDR magnet contains a multi-domain structure when the magnet is thermally demagnetized or when the applied field is relatively small. However, the HDDR magnet has only a single-domain structure after the application of sufficiently large fields.

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This paper presents results obtained from a numerical simulation of the magnetizing Nd-Fe-B magnets by using the three-dimensional Variable Magnetization and Stoner-Wohlfarth (VMSW) method combined with the finite element method (FEM) and external circuit equations. The initial magnetization curves of rare-earth permanent magnets measured with a magnetizer were used in the simulation. The calculated results were compared with the measured results to verify the numerical method of the simulating magnetizing process.

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We have demonstrated the ultrafast switching of the magnetic state from a spin glass insulator with short range charge and orbital order (CO/OO) to a ferromagnetic metal in the course of photoinduced phase transition utilizing the strong phase competition in perovskite-type Gd_0.55Sr_0.45MnO₃. The femtosecond Kerr rotation and reflectivity measurements, which detect the spin and charge dynamics, respectively, have revealed that the metallic state is formed just after the photoirradiation, however, magnetization increases with the time constant of 0.5 ps. The delayed increase of the magnetization is attributable to the magnetic-field-induced alignment of ferromagnetic domains in the initially produced metallic state.

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Herein, we introduce a classical expression for describing a spin-polarized current, and propose the effect of a spin-polarized current with a spatial distribution in a micromagnetic framework. The electric current was calculated on the basis of the resistance between neighboring cells in the calculation region. The effect of a spin-polarized current crossing a domain wall in a thin and narrow permalloy strip with a notch was elucidated by micromagnetic calculation. When the magnetic strip has a notch, the highest current density around the notch in the magnetic strip is dominant for domain wall motion. The critical current density increases as the notch size increases. Below the critical current, the domain wall tends to vibrate around the notch. The natural frequency of the wall vibration spectrum increases as the notch size increases, whereas it is almost independent of the current density.

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Interlayer-exchange-coupled (IEC) type spin-valve giant magnetoresistive (SVGMR) films in which the pinning layer does not contain an anti-ferromagnetic layer have been investigated. The IEC-type SVGMR films had good SV properties with a 10% MR ratio as deposited. However, the MR ratio decreased with increasing annealing temperatures over 310°C. From cross sectional TEM observation, interfacial roughness between the free and pinned layers was increased by annealing, and such roughness causes the degradation of SVGMR properties. Thermal stability of SVGMR films was improved when the thickness of Ta capping layer was 5 nm. In order to reduce the thickness of capping layer, various materials of Ru, Cu, and NiFeCr were investigated instead of Ta. No degradation in SV properties after 320°C annealing was achieved with the 2 nm of Ru capping layer.

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The crystallographic structure of Mn-Ir layers and the exchange anisotropy of Mn-Ir/Co-Fe bilayers were investigated for various process pressures and sputtering gases used in the deposition of the Mn-Ir layers. When Ar was used as the sputtering gas, the unidirectional anisotropy constant J_K was found to decrease with decreasing Ar pressure P_Ar. However, in the case of Kr gas, J_K was shown to be constant at about 1.0 erg/cm², regardless of the Kr pressure P_Kr. In particular, J_K exceeded 1.0 erg/cm² for P_Kr ≤ 0.1 Pa. The x-ray diffraction profiles showed that superlattice diffractions from the ordered Mn₃Ir phase were detected around the pressures P_Ar = 0.2 Pa − 2.0 Pa and P_Kr = 0.04 Pa − 2.0 Pa. In the case where P_Ar ≤ 0.1 Pa, the damage caused by the recoiled Ar ions is suggested to be the origin of the decreasing J_K and the disappearance of Mn₃Ir phase.

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Fe thin films were prepared on MgO(100), MgO(110), and MgO(111) substrates by UHV-MBE. The film growth structure and the magnetic properties were investigated. In-situ RHEED observation showed that epitaxial Fe thin film with the (100)_bcc, (211)_bcc, and (110)_bcc planes parallel to the substrate surface grew on respective MgO substrates at elevated temperatures. The Fe(100)_bcc film formed on MgO(100) is a single crystal, while the Fe(211)_bcc films on MgO(110) consists of two domains with a twin relationship. The Fe(110)_bcc film on MgO(111) consists of two types of sub-domains with Nishiyama-Wasserman and Kurdjumov-Sachs epitaxial orientation relationships. A 0.3%-0.5% reduction of the lattice spacing perpendicular to the substrate surface was observed by X-ray diffraction for Fe thin films prepared at a substrate temperature of 200°C. This reduction decreases with increasing the substrate temperature for the MgO(100) and (111) substrates. The in-plane magnetic anisotropy measured for three epitaxial films reflects the magneto-crystalline anisotropy of bulk Fe crystal.

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Fine Fe particles encapsulated in carbon cages were synthesized by employing both arc and surface wave plasma discharge techniques. The size of synthesized nanocapsules ranged from several 10s nm to 10 μm in diameter, which was approximately one order of magnitude larger than that of nanocapsules synthesized by the arc discharge method. The transmission electron micrographs revealed that the Fe particles were encapsulated in graphite shells. The selected-area electron diffraction patterns indicated that the Fe particles were single crystals. The fraction of a-Fe, g-Fe and Fe3C components in the nanocapsules synthesized under the total gas pressure of 1.0 kPa were estimated to be 83, 6, 11 wt%, respectively.

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GMR multilayer films using Co₂MnGe(CMG) and Mn-Ir/CMG exchange-coupled films were fabricated on thermally oxidized Si substrate, and their crystal orientation, magnetic properties, and interfacial roughness were investigated. The main results are stated as follows. (1) (100) oriented MnIr/CMG exchange-coupled films were realized when Ni-Ta underlayer/Cr buffer layer were deposited on thermally oxidized Si substrate. After thermal annealing for 2h at 250°C in a magnetic field of 5 kOe, the unidirectional anisotropy constant (J_K) of bilayers was 0.13 erg/cm². (2) Dependence of saturation field (H_s) on Cr thickness for GMR films with (100) oriented CMG/Cr/CMG trilayer was investigated. H_s was minimum when Cr thickness was 1 nm and 5 nm. (3) Surface roughness (R_a) of Ni-Ta 5 nm on Al-Cr bottom electrode layer(100 nm) was 0.108 nm. (4) Flat and (100) oriented CMG/Cr films was formed on Al-Cr bottom electrode layer (100 nm)/Ni-Ta underlayer (15 nm)/Cr buffer layer (60 nm) when Cr content of the Al-Cr layer was 18.7-24.6 at%.

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Patterned magnetic dots were fabricated by an Artificially Assisted Self-Assembling (AASA) method, and the dot size dispersion was estimated. In AASA method, self-assembled polymer dots are formed in a groove guide and are used for the etching mask. It is found that the dispersion of the size of the magnetic dots (average diameter: 23nm, average pitch: 45nm) can be reduced by optimizing the guide shape. Decreasing the molecular weight of the polymer is also found to be effective to reduce the dot size dispersion. Dispersion of 10.6 % was achieved using a hexagonal guide. This feature is advantageous to the patterned magnetic recording media compare to the electron beam lithography, where the dispersion is increased with the patterning size.

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The dynamic magnetization process is studied in CoFeB films for high frequency application by using a time-resolved imaging technique. The domain wall mobility of 12 m/sOe was observed at the resonant frequency of 220 kHz. The effective wall mass, viscous damping constant, and restoring force constant were evaluated in CoFeB films.

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Metallic iron (Fe) nanoparticles have been synthesized by reducing SiO₂-coated magnetite (Fe₃O₄) nanoparticles. The Fe₃O₄ nanoparticles with an average diameter of about 10 nm were prepared by thermal decomposition of the iron-oleate complex, and were subsequently coated with SiO₂. The SiO₂-coated Fe₃O₄ nanoparticles were annealed at various temperatures for 2 hr in flowing H₂ gas to convert them to Fe nanoparticles. The Fe₃O₄ nanoparticles with 3- and 5-nm SiO₂ coatings were completely reduced to Fe nanoparticles at 800°C. However, under these conditions, coalescence of thus-formed Fe nanoparticles was also observed. The Mössbauer spectrum of the Fe nanoparticles prepared by annealing at 800°C revealed that about 84% of the nanoparticles were ferromagnetic α-Fe at room temperature. Approximately 16% of the Fe nanoparticles were paramagnetic due to superparamagnetic-like behavior at room temperature.

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We have investigated the preparation, structures, and magnetic properties of bulk Fe₂CrSi and Fe₂Cr_1-xTi_xSi Heusler alloys. Although a Cr-rich secondary phase coexists with the Heusler mother phase in stoichiometric Fe₂CrSi samples, high temperature annealing (1200°C) effectively reduces the extent of the Cr-rich secondary phase. We found that pure single-phase samples can be prepared in a narrow composition range of 22% Cr. For a Fe₂Cr_1-xTi_xSi system with Ti content x of up to 1/8, virtually single-phase Heusler alloys have been obtained. The saturation magnetization of Fe₂Cr_1-xTi_xSi decreased with increasing Ti content, while their Curie temperatures T_c remained constant.

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MgO (100) textured films can be prepared by reactive facing targets sputtering at room temperature when they were deposited on (100) oriented Fe buffer layers. This method allows fabrication of perpendicular magnetic tunnel junction (p-MTJ) with MgO tunneling barrier layer and rare-earth transition metal amorphous alloy (RE-TM alloy) thin films as perpendicularly magnetized layers. The 3nm-thick MgO tunneling barrier layer in p-MTJ multilayer prepared on a glass substrate revealed (100) crystalline orientation. Anomalous Hall effect measurement clarified that the 3nm-thick Fe buffer layers attached to the two end of MgO tunneling barrier layer magnetized vertically to the film plane because of the strong exchange coupling with RE-TM alloy layers. TMR ratio of 31% was observed in the multilayered p-MTJ element.

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The rectifying effect of spin-polarized radio-frequency (RF) current through ferromagnetic resonance is found in a single-layered ferromagnetic wire. The direct current (DC) voltage is generated by the magnetoresistance oscillation and the planer Hall effect due to the magnetization precession by the RF current. We show that the application of DC current with RF current is possible to excite the additional spin wave modes, detected by using a technique of microwave rectification.

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We calculated the temperature and voltage dependences of the tunnel magnetoresistance (TMR) ratio for ferromagnetic junctions with Heusler alloys using a phenomenological model that takes into account the spin-flip tunneling process. We simplified the density of states calculated with first principles and used it to calculate TMR. We found that spin-flip tunneling makes the dependence of TMR on voltage large and asymmetric. The relevance of the calculated results to experimental analysis is argued.

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La_0.7Sr_0.3MnO₃ (LSMO) polycrystalline thin films were prepared by sputtering on YSZ (yttria stabilized zirconia) /Ba_0.4Sr_0.6TiO₃ (BSTO)-buffered Si substrate. The grain sizes of LSMO films were controlled by changing the substrate temperature and thickness of the BSTO buffer layers; we then investigated the low field magnetoresistance of LSMO films. We found that MR increased with decreasing LSMO grain sizes and increasing film resistivities. The results and mechanism of MR are discussed in terms of the register-network model based on intergrain spin polarized tunneling.

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Current-Perpendicular-to-Plane Giant MagnetoResistance (CPP-GMR) spin valves with a Current-Confined-Path (CCP) Nano-Oxide Layer (NOL) were investigated from the viewpoint of the relation between MR ratio and nanostructure. We have reported that the CPP-GMR spin valves with the CCP-NOL fabricated by Ion-Assisted Oxidation (IAO) show higher MR ratio than those fabricated by Natural Oxidation (NO). In this report, the nanostructures of CPP-GMR spin valves are compared by means of the high-resolution Transmission Electron Microscope (TEM) and the Fast Fourier Transform (FFT) map. It was confirmed that IAO is effective for improving the crystalline structure not only for the CCP, but also for the free layer on the CCP. The well crystalline structure can decrease the resistivity of the metal path and enhance the spin-dependent scattering inside the free layer, which are considered to be the reasons for the enhancement of MR ratio for the IAO.

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Spin dependence of the conductance, that is, the spin-injection efficiency, of photo-excited electrons has been calculated for Fe/GaAs with a Schottky barrier by using a realistic tight-binding model. The conductance calculated by taking k_|| summation, where k_|| is the momentum of tunneling electrons parallel to layer planes, has been found to be strongly dependent on the height of the Schottky barrier, and the spin dependence of conductance may change the sign. We found that the latter result is caused by interfacial states near the contact between Fe and GaAs layers.

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Detailed spin-transfer switching (STS) properties in the nanosecond regime were investigated. We prepared a CoFeB/MgO/CoFeB magnetic tunnel junction that exhibits a 115 % magnetoresistance ratio. The STS property in the ≥ 2 ns region was obtained by static measurement. We then examined this property from several points of view. In addition, we outlined a new method of real-time switching observation. That is expected to clarify the STS mechanism directly. Using this method, the contribution of the thermal activation effect in a switching current below I_C0 was successfully detected. This indicates that the real-time method has the advantage that it clarifies the STS mechanism.

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The TMR (Tunneling Magneto-resistive) junctions of SiO₂-sub./bottom-electrode/IrMn/CoFe/Al-oxide/NiFe/ top-electrode were fabricated. We have succeeded to observe both high sensitivity and linearity in a low magnetic field for the optimized TMR junctions. The circuit of magnetic sensor using developed TMR junctions exhibited high output signal enough to resolve over 36 directions at terrestrial magnetism. The terrestrial sensor using TMR junctions is very small size and low energy consumption, so will be key “tools” for some solutions, for example, a navigation sensor with Global Positioning System(GPS) in cell phones.

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A giant magnetoimpedance element with a step-like impedance property was obtained in the case of amorphous Co₈₅Nb₁₂Zr₃ soft magnetic thin film in a rectangular shape with an in-plane uniaxial easy axis at an angle of approximately 60 degrees relative to the width direction of the element. It was shown experimentally that the magnetic field in which the step-like impedance change occurs has an almost constant value, with a standard deviation in the micro tesla (μT) range, when an alternating magnetic field of constant amplitude is applied. There is a possibility of applying this phenomenon to a magnetic switch. This application requires a constant impedance step-point uninfluenced by the route or amplitude of the external magnetic field. In this paper, a variation of the magnetic field in which the impedance step occurs as a function of the range of the alternating magnetic field is studied. As a result, a stability of less than 20 mOe (1.6 A/m) at about 1200 mOe (96 A/m) is obtained for the impedance step-point, with consideration given to every experimental condition of the range of applying magnetic field. This result means that it is possible to make a magnetic switch with a switching field accuracy of less than 2%.

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We attempted to control the magnetic anisotropy of a high-frequency carrier-type magnetic field sensor by means of shape anisotropy. We examined the size of element necessary to realize low anisotropy strength both experiment ally and theoretically. The theoretical results agreed well with the experimental ones, and we were able to calculate the size of an element with low anisotropy strength theoretically.

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A directional coupler using a CoFeB magnetic/polyimide dielectric hybrid transmission line was fabricated and evaluated under a large-signal transmission condition from 0.5 to 2 W. The device consists of a [polyimide (1μm)/CoFeB (1μm)/polyimide (1μm)] sandwich between upper Cu coupled lines (3μm thick and 12μm wide) and a lower Cu ground plane (3μm). The electromagnetic coupling between the top main line and the sub-line is composed of the electric field coupling due to the stub capacitors and the magnetic field coupling through the inner magnetic film. The fabricated CoFeB magnetic thin film directional coupler exhibited excellent large-signal transmission characteristics even at a rating power of 2 W in a real cellular phone application. In addition, such a large-signal characteristic was acceptable for a wideband frequency of 0.8 to 2.4 GHz, which was mainly due to the non-resonance operation.

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A new active compensation method using magnetic repulsion is presented which is applicable to a separate magnetic shield. A pair of the compensation coil is set on each of the separate shells and generate compensation magnetic field to bend the flux lines of the disturbing magnetic field in order to pass them below and above the magnetic shells. We have applied the method to a small laboratory model and confirmed a large shielding efficiency of the new compensation method. The transverse shielding factor measured perpendicularly to the plane separating two shells was 1.4 for the magnetic field of 10 Hz, 10 μT, when the compensation was off, however, it was larger than 1,000 when the compensation was on.

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The resolution of an electron beam lithography system (EBLS) is affected by low frequency magnetic noise due to trains, cars, elevators, and electrical devices. Active shielding, in which magnetic noise is shielded by compensation coils, can obtain a high shielding factor at low frequencies and provide better cost performance and flexibility than magnetically shielded rooms. In this paper, four configurations for the compensation coils of an active shield were proposed (large and small two- and four-square coils). Experiments using the EBLS model and 3-D magnetic field computations were carried out to find an optimal configuration for the compensation coils and for the position of the pickup sensor outside the EBLS, where the magnetic disturbance inside the EBLS could effectively be reduced.

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Wind power generators are well known as renewable sources of energy and permanent-magnetic reluctance generators are expected to be used for these. Although they can generally be simulated using the finite element method, this is not suitable for complex systems such as wind power generators. We simulated wind power generation using a permanent-magnetic reluctance generator with a DC micro grid system. The results revealed the possibility of implementing a wind power generation system.

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A parametric motor using parametric oscillation phenomena, offers numerous attractive features not found in conventional motors, such as overload protection, simple construction, low cost, and less noise. However, there are abnormal phenomena, such as normal-reverse rotations and intermittent rotations in the motor. The basic operating equation for these motors can be represented using a Mathieu differential equation. This paper discusses the relationships between the stability of parametric oscillations and the nonlinear terms that compose the Mathieu equation. As a result, the relationships between them are made clear and the guiding principle of design of the motor is obtained.

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We earlier proposed a parametric motor using a laminated Si-Fe core. This paper discusses the relationship between the width of inner and outer ring core and the performance characteristics of the motor in order to establish a design method of the motor in the future. The characteristics of test motors, such as output and efficiency, were deteriorated by making the width of inner or outer ring core of a prototype parametric motor increase or decrease. We measured the magnetic flux density in the stator of those motors in order to find the reason.

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We earlier proposed a new type of three-phase induction motor excited by a single-phase power supply that may be useful for conserving energy in the future. However, in order to practically use the motor, the output power and efficiency need to be further improved. Therefore, the distribution of magnetic flux density in the stator should be suitable one for the three-phase. This paper discusses the effect of magnetic anisotropy in the stator core on the performance characteristics of the motor.

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A variable inductor consists of magnetic cores and primary and secondary windings. It can regulate the effective inductance of the secondary winding by dc excitation from the primary winding. Variable inductors are expected to be applied to reactive power compensation in electric power systems, because they have a simple robust structure that is extremely reliable. This paper proposes a novel three-phase variable inductor to reduce size and weight. First, the operating principles of the proposed variable inductor are explained. Next, basic characteristics of the proposed variable inductor we calculated by reluctance network analysis (RNA) and the finite element method (FEM) are presented, which we compare with those of a conventional EIE-core variable inductor.

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We studied a three-phase parametric motor excited by a single-phase power supply. We carried out many experimental evaluations to improve the characteristics of the motor. An analytical technique was necessary to further improve the motor characteristics and to optimize its design. In the past, we demonstrated the validity of applying reluctance network analysis (RNA) to the dynamic analysis of a laminated core parametric induction motor, which is a basic three-phase parametric motor. Consequently, we applied RNA to a single-phase input three-phase parametric motor.

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Communication lines in wire communication systems are usually used as power lines. The AC communication signal and DC supply power are separated at the input part in a powered terminal. Conventional wellknown separators utilize the combined circuits of inductors and capacitors. When the frequency of the signal is at its lowest, the inductance increases, making it necessary to have a large inductor. A conventional electronic choke circuit using transistors has the disadvantage of high power dissipation. Furthermore, the direction of the DC current is limited to unidirectional. Our original communication system consists of powering terminals with low-power DC-DC converters and the terminals they power. The direction of the DC current in the powering terminals is opposite to that in the powered terminals. Therefore, it is preferable to have a bidirectional electronic choke. In this paper, a new low-loss electronic choke with small inductors and amplifiers is proposed. This circuit is composed of a high input-impedance buffer and a signal canceller. Input-impedance and other characteristics are investigated through an experiment and analysis.

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