To investigate the influence of the variation of the write track width in the discrete track recording, we calculated the off-track capability (OTC) of the write/read head using Landau-Lifshitz-Gilbert micromagnetic simulations. Recently, the OTC has become increasingly important in the system design of the hard disk drive (HDD). As for the write head, it is a serious problem that the write track width varies significantly in the manufacturing processes. In the simulations, we evaluated the OTC of the wite/read head as a function of the write track width on both conventional and discrete track media from the viewpoint of the signal-to-noise ratio (SNR). As a result, we found that the OTC of write/read head on discrete track media was superior to that of conventional media for variations of the write track width.

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  A master pattern with the a line-and-space (L/S) part and a checker part in the servo signals was made by using an FeCo film, and the edge printing characteristics of both parts were compared. The MFM output in the checker part was equal to the L/S part for a bit length of 200 nm, while for a bit length of 100 nm, the MFM output in the checker part decreased by about 30% compared with that in the L/S part, because of the MFM’s low resolution. However, for a bit length of 100 nm, simulation results showed that the edge-printed magnetization of the checker part was equal to that of the L/S part. When the TMR head reproduced both parts, the output in the checker part was equal to that in the L/S part. The optimum printing field for the checker part was the same as that for the L/S part. Moreover, the rate of decrease in the MFM output did not depend on the printing field.

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  Technologies for realizing areal recording densities of over 1 Tbit/inch² in hard disk drives have been aggressively developed. At such high densities, it is necessary that a read head should be able to sense a weak magnetic field straying from a recorded medium. One of the most promising candidates for such a head is a current-perpendicular-to-plane giant magnetoresistive (CPP-GMR) head. However, it has been pointed out that in a CPP-GMR head, injection of polarized spin into a free layer causes spin-torque noise, which is peculiar to CPP-GMR heads. Several experimental and theoretical results on spin-torque noise have been reported. Thus, it is necessary to investigate the relationships of spin-torque noise with various parameters of a CPP-GMR head. In this paper, the dependencies of the spin-torque noise power and spectrum on the amplitude of the sense current density, its polarity, and the amplitude of the exchange interaction acting on the pinned layer are investigated by means of micromagnetic simulation. As a result, it is clarified that the noise properties are strongly influenced by the polarity of the injected spin, and that the noise power spectrum is located in narrow regions of frequency space.

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  The magnetic spacing of both longitudinal and perpendicular Ba-ferrite particulate tapes was evaluated in comparison with that of metal particulate tapes. First, the effective spacing, which is the sum of the magnetic spacing and the transition parameter, was determined by fitting the wavelength response to Wallace's equation. Next, the transition parameter was obtained from a magnetic force microscopy image. Finally, the magnetic spacing was calculated as the difference between the effective spacing and the transition parameter. Both the transition parameter and the magnetic spacing of both longitudinal and perpendicular Ba-ferrite particulate tapes were much smaller than those of metal particulate tapes. These results indicate that Ba-ferrite particulate media have a considerable advantage over metal particulate media in high-density recording.

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  The stability of recorded magnetization on hard disk drives (HDDs) is influenced by external environments, such as temperature and magnetic fields. Small scratches are frequently formed on an HDD medium surface on contact with the magnetic head. The influence of a perpendicular magnetic field and mechanical scratching on the magnetization structural stability of perpendicular recording media was investigated by using a magnetic force microscope. The magnetization structure started to change at lower magnetic fields in an area near and below mechanical scratches when compared with normal areas with no scratches. A quantitative analysis of variations in the magnetization structure was carried out by taking into consideration the difference in MFM images observed for the same sample area before and after exposing the sample to different magnetic fields.

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  In this study, the influence of the Pt content in a perpendicular anisotropy master medium (PAMM) on the bit printing characteristics was investigated through experiments and simulation. As a result, the most excellent printing characteristics were obtained with a Pt content of 10% to 20%. This result could be explained by the fact that the anisotropy and the saturation magnetization corresponded to the Pt content of the PAMM. The optimum printing field of the PAMM was about 1kOe smaller than that of a pure Co or conventional master medium.

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  We investigated the effect of transition curvature on track edge noise through experiments and calculations. We measured and calculated two types of recording heads that had similar magnetic write widths, but different transition curvatures. In both the measurements and calculations, the track edge noise increased more at high linear density with the head with larger transition curvature, due to its wider erase band, which was considered to be noise source at the track edge. We also clarified that reducing the transition curvature was effective to increase signal-to-noise ratio (SNR), especially at high linear density, and that reducing the track edge fluctuation was effective to increase SNR, especially at low linear density. Therefore, reducing both the transition curvature and track edge fluctuation is necessary to reduce track edge noise and consequently achieve high areal density.

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  The perpendicular magnetic printing characteristics on exchange coupled composite (ECC) media are investigated using micromagnetic simulation. It is clarified that magnetic printing onto ECC media is feasible. Master patterns were clearly printed onto ECC or semi-ECC media with coherent rotation of magnetizations in hard and soft layers. The optimum printing characteristics in ECC or semi-ECC media is the same as that of single-layered (SL) medium. When the thermal stabilities in SL and ECC media are the same, the optimum printing field for ECC medium is lower than that of SL medium. To obtain sufficient printing characteristics in ECC media, the ECC media need stronger interlayer exchange coupling than that of semi-ECC media.

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  We examined the relationship between media cluster size distribution and signal quality to obtain a guideline for developing high-density recording media. Both spin-stand measurements and micromagnetics simulations were used. The cluster size distribution and SNR of various recording media were evaluated, and the relationship between the two was analyzed using multiple regression analysis. The results demonstrate that the media SNR could be quantitatively estimated from the cluster size distribution (both average sizes and size deviations). Although reducing either the average size or the size deviation was effective in terms of improving theSNR, the impact of the average was much larger. On the other hand, we also found that the effect of size deviation increased for the smaller average-sized media. We concluded that providing the guidelines for each individual developing medium is a key step and that the proposed analysis method is therefore effective.

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  L1₀-ordered FePtCu ternary alloy thin films with (001) preferential orientation were fabricated from Cu/Pt/Fe trilayers to maintain their Curie temperature at a level suitable for the operating temperature of recording media in a heat-assisted magnetic recording (HAMR) system. It was confirmed that the addition of Cu to FePt films reduces the Curie temperature of the FePtCu films to a level lower than that of FePt films. The Cu content ratio of FePtCu films was controlled by adjusting the Cu layer thickness of the Cu/Pt/Fe trilayers. With increasing Cu thickness, their Curie temperature dropped below 300 degrees C and their perpendicular coercivity decreased to a sufficiently low level of about 1kOe.

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  The uniaxial magnetic anisotropy field, H_k, and g-factor of a c-plane oriented CoPtCr alloy film was quantitatively evaluated by using Q-band (∼34 GHz) ferromagnetic resonance (FMR). An FMR signal with a high signal-to-noise ratio was successfully obtained by using a 2mm^φ-Macor holder, which achieves phase matching, a decrease in the background of the signal, and accurate alignment of the external field parallel to the film normal or in-plane. An external field was applied perpendicularly or horizontally to the film, and a single magnetic domain was maintained during the measurements. The measured FMR signals demonstrated that 1) the H_k and g-factor were simultaneously derived for CoPtCr films with Co 75-90 at.%, 2) the magnitude of H_k was supported by that obtained with a Torque magnetometer, and 3) the g-factor increased from 2.11 to 2.19 when Co content was decreased from 85 to 65 at.% and the Cr content was increased from 5 to 20 at.%.

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  Magnetically soft amorphous particles were successfully synthesized in aqueous solutions. The advantages of the particles are their high saturation magnetization and submicron size. In addition to the original synthesizing process, particle precipitation in a magnetic field is studied. In the process of precipitation in the magnetic field the particles are bonded into long chains leading to an appreciable reduction of the demagnetizing field that has been an obstacle to the high-permeability performance of soft magnetic particles. The microstructures, magnetic softness of the chains, and significant enhancement of the permeability in the frequency range 0.05∼10 GHz are demonstrated.

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  (Co₃₅Fe₆₅)B magnetic films with an Ru underlayer were fabricated and characterized using a triple carrousel sputtering method. The high velocity movement of a substrate brought that the Ru underlayer and B enhanced uniaxial anisotropy field with increasing elongation of the lattice parameter, preferred orientation in the CoFe crystalline bct phase. In this study, we examined the uniaxial anisotropy field by using a simulator of sputtering particles deposited on a substrate moving at high velocity. As a result, we found that an anisotropic incidence existed. The simulation result suggested that sputtered Fe and Co particles in the range of energy had the potential of those oblique incident in the direction of the substrate movement.

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  Ba₃Co₂Fe_24(1-x)O_41-δ(x=0∼0.05) samples were prepared by using a conventional ceramic method. The samples had the single crystallographic phase of hexagonal Z-type ferrite. Ba₃Co₂Fe_24(1-x)O_41-δ with x =0.05 had a μ’ of 8.9 and a maximum quality factor of 66.9 at 100MHz. Because of the decrease of iron content, loss of domain wall motion is reduced. In addition, the decreases of Fe²⁺ ions reduces the effect of eddy current, which may cause to improve initial permeability and quality factor.

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  Experiments were carried out to investigate the effects of composition, heat-treatment, and nitrogenation conditions on the magnetic properties of Sm-Fe-Co-Ti-Zr-Y-N compounds with a TbCu₇-type structure. The optimum preparation conditions for the compounds were: composition: {Sm₁₀(Fe_0.9Co_0.1)_88.7Ti_0.3Zr_0.5 Y_0.5}_85.6N_14.4, roller velocity: 50m/s, heat treatment: 660°C for 60min in high-purity Ar gas, and nitrogenation conditions: 420°C for 10h in high-purity N₂ gas. Typical magnetic properties of the obtained compound powders were: J_r=0.98 T, H_cJ=751.5kA/m, H_cB=544.7 kA/m, (BH)_max=147.0 kJ/m³ (18.5 MGOe), and T_c=510°C. We found that a sample made from these compound powders was an exchange spring magnet from the recoil loops of the hysteresis curves, X-ray diffraction patterns, and σ-T (Magnetization-Temperature) curves. The value of (BH)_max for an isotropic compression-molding bonded magnet prepared by using {Sm₁₀(Fe_0.9Co_0.1)_88.7Ti_0.3Zr_0.5Y_0.5}_85.6N_14.4 powder was 92.7 kJ/m³ (11.7 MGOe), when the density of the bonded magnet was 6.08 Mg/m³. The average reversible temperature coefficient of J_r was α(J_r)_ave. =-0.05%/°C, and the temperature coefficient of H_cJ in a range from 25 to 125°C obtained by linear extrapolation was α(H_cJ) =-0.46 %/°C.

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  In order to trace the annealing temperature dependence of the coercivity in sintered Nd-Fe-B magnets systemtically, we examined a single successive annealing (SSA) method, in which the coercivity value of a single sample is successively recorded after each annealing cycle at T_a= 400°C-710°C with increments of ΔT_a = 10°C. In addition to the coercivity values, we paid special attention to the shapes of demagnetization curves, in terms of the differential susceptibility versus magnetic field plot, which provides information on the nucleation field distribution (NFD). Samples with small amounts of Cu additives showed a more significant temperature dependence of the coercivity than those without Cu additives.

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  The Co₃₅Fe₆₅ magnetic films with Ru underlayer were fabricated using a special RF-magnetron sputtering method and characterized. The underlayer coating effect of improving soft magnetic properties for the GHz frequency use was investigated relating to the surface roughness and thickness of Ru underlayer and the crystalline structure and orientation of as-deposited magnetic layers.
  The coating of the underlayer with thickness of 10-30 Å was so much effective to achieve a high uniaxial magnetic anisotropy field of 1000 Oe with the low coercivity less than 10 Oe for the higher driving frequency (ferromagnetic resonance frequency over 10 GHz), by inducing about 1% elongation of lattice parameter in the c direction of_the bct Co-Fe magnetic phase, preferred crystalline orientation of (110), (200) of the bct Co-Fe magnetic phase, and about 60% decrease of crystallite size in the Co-Fe layer. The (110) plane was preferentially parallel to the film plane and the elongated lattice in the c direction was oriented preferentially parallel to the easy magnetic axis in accord with the direction of the (200) plane space.

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  The current-driven domain motion of a multi-wall in a magnetic nanowire with perpendicular magnetic anisotropy was analyzed in this study by using micromagnetic simulation. As a result, we found that there were two modes in the multi-wall motion, and the motion was determined by the applied current density and non-adiabatic spin torque parameters; this was similar to single-wall motion. The x-component of magnetization in the domain wall exhibited different behavior according to the current density. The bit length was extended for a low current density and the bit length was varied for a high current density due to interaction between the magnetic domain walls.

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  The dependence of the exchange stiffness constant on current-driven domain wall motion in a magnetic nanowire was examined through micromagnetic simulation. As a result, we found that the critical current density changes according to the width of the domain wall at the edge of the nanowire.

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  The electrical resistivities and Hall effect of Cr_1-xV_x alloys(x<0.04) were measured at high pressure. The Néel temperature T_N of x = 0.015, 0.032 and 0.035 was found to disappear at corresponding P_c of 5.6 GPa, 1.1 GPa and 0.7 GPa, respectively. The Hall coefficients of x = 0.032 and 0.035 demonstrated a discontinuous change around P_c, which implies a quantum phase transition induced by high pressure. We found that the exponents in the power law of resistivity of x = 0.015 had an anomaly around P_c, which means that the large quantum fluctuations affect the resistivity even at high temperature. A possibility of superconductivity is explored near P_c for x = 0.032. A slight decrease in the ρ(T) curve was observed below 1 K at high pressure. The origins for that are briefly discussed.

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  Ni epitaxial thin films were prepared on Au(100)_fcc underlayers hetero-epitaxially grown on MgO(100)_B1 single-crystal substrates by ultra-high vacuum molecular beam epitaxy. The effects of substrate temperature on the structural and the magnetic properties were investigated. hcp-Ni crystals are successfully obtained at temperatures lower than 300°C. With increasing the substrate temperature, the volume ratio of more stable fcc phase increases in the film. The hcp-Ni crystal consists of two types of (11-20) domains whose c-axes are rotated around the film normal by 90°each other. X-ray diffraction shows that the Ni film prepared at 100°C consists primarily of hcp crystal. An atomically sharp boundary is recognized at the Ni(11-20)_hcp/Au(100)_fcc interface for the Ni film. The in-plane magnetization properties of hcp-Ni film are interpreted to be reflecting the magnetocrystalline anisotropy of bulk hcp-Ni crystal which was predicted by a computer simulation study.

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  Strontium ferrite thin films have been deposited on Corning glass with Au underlayer by using DC magnetron sputtering system. Au island structure can be formed on Corning glass by heating the substrate over 100°C. In order to achieve higher Au dot density and consequently higher density of SrM, an attempt to decreasing Au thickness has been carried out. The maximum of coercivity and remanent squareness ratio in perpendicular direction are almost constant at 2.3kOe and 0.45, respectively, at Au underlayer thickness from 4nm to 8nm. The magnetic interaction between SrM grains prepared on Au nano-dots is less than that for the continuous film.

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  Multi-layered thin films of BaTiO₃ and CuFe₂O₄ were deposited by diode rf magnetron sputtering method. The samples which consist of different number of layers were prepared and then they were annealed at 973 K in air.The crystal structure and magnetic properties of these samples were examined by a X-ray diffractometer and avibrating sample magnetometer, respectively. The magneto-electric (ME) effect of these multi-layered thin films wasmeasured by applying the direct-current magnetic field and the alternate-current magnetic field in parallel. As aresult, ME coefficient (α_E) of the 3 layered sample indicated maximum value of about 300 mV/cmOe at a bias magnetic field of 2.4 kOe. The ME coefficient decreased with the increasing of the number of layers.

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  The unidirectional anisotropy constant, J_K, of γ-Mn-Ir / FM (FM = Fe-Co-Ni) bilayers was investigated by systematically changing the composition of the Fe-Co-Ni layers. The FM layers were grown in the crystal structures corresponding to their composition on the (111)-oriented face centered cubic (fcc) Mn-Ir layer. J_K was significantly changed around the phase boundary of the FM layer between the body-centered cubic (bcc) phase and fcc-phase. The experimental results revealed a general feature where bcc-structured FM layers were more likely to induce stronger exchange anisotropy than fcc-structured FM layers. The J_K values and the lattice mismatch between the Mn-Ir layer and the FM layer were increased with increasing Co concentration in the bcc-FM region. The dependence of J_K on FM composition have been explained qualitatively with lattice distortion at the interface between the Mn-Ir and FM layers.

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  The changes in voltage-induced magnetic anisotropy were investigated in an epitaxial magnetic tunnel junction structure. Perpendicular magnetic anisotropy of the ultrathin FeCo layer could be confirmed from thesaturation properties of the TMR curve measured under in-plane magnetic fields. The aturation field was clearly changed by the application of bias voltages, which implies that the change in voltage-induced anisotropy was achieved in the magnetic tunnel junction structure.

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  Perpendicularly magnetized magnetic tunnel junctions (MTJs) were fabricated by depositing thin L1₀-ordered FePt films on MgO(001) substrates using a UHV sputtering system, and the dependence of structural, magnetic, and magnetotransport properties of the junctions on the thickness of the FePt layers was investigated. A full epitaxial structure of MgO(001) sub./Cr/Pt/FePt/MgO/CoPt/Ta was observed. The tunnel magnetoresistance (TMR) ratio was measured to be 6% at room temperature, and magnetization switching was clearly observed in the thin FePt layer. Transmission electron microscopy (TEM) observations revealed that the interface between FePt, MgO, and CoPt layer has strain due to lattice mismatch, which might be a reason for the low TMR ratio.

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  We investigated Spin Torque Oscillation (STO) excited by spin-polarized currents in Current-Perpendicular-to-Plane (CPP) spin-valve devices with Fe/AlO_x-Nano-Oxide Layer (NOL) that had Nano-Contact MagnetoResistance (NCMR). From the R-H curve, at the applied current, the magnetization state of the free layer is affected by an Oersted field and Spin Transfer Torque (STT). At positive current, the dependence of applied field demonstrated a blue shift, while, at negative current it demonstrated a red shift. Under 250-350 Oe multiple modes, low-level oscillations and wide FWHM were observed, while, under 360-500 Oe single modes, high-level oscillations and narrow FWHM were observed at positive current. Moreover, under 250-350 Oe, the dependence of applied current on oscillation frequency demonstrated a red or blue shift, while, under 360-500 Oe, it demonstrated blue shift. The blue shift oscillations under the applied current were considered to have originated from coherent out-of-plane precession near nano-contacts on the free layer side.

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  A Stress-Assisted Magnetization Reversal (SAMR) method has been demonstrated in a perpendicular GMR multilayer to reduce a power consumption during the magnetization-reversal process in a perpendicular magenetoresistive random access memory. A giant magnetoresistive multilayer of Cu(15nm)/Terfenol-D(10nm)/Cu(3nm)/TbFeCo(30nm)/Cu(15nm) was prepared. The perpendicular components of magnetization reversal in the GMR multilayer were observed during the SAMR process by using the anomalous Hall effect. As a result, the magnetization of a free layer was shifted from perpendicular to in-plane under the application of a stress of 279MPa.

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  To comprehend the influence of lattice distortion in a Heusler alloy, the structural and electrical properties of epitaxial thin films of Fe₂VSi on (001) MgAl₂O₄ and MgO substrates, were investigated. Structural characterization revealed that the films on MgAl₂O₄ (a lattice mismatch to Fe₂VSi of 0.7 %) were in tetragonally strained states, while the films on MgO (lattice mismatch of 4.9 %) were in relaxed- strain states close to a cubic lattice. We will also demonstrate that the epitaxial strain imposed by the substrates significantly modifies the physical properties of the films, and enhances the antiferromagnetic transition temperature of Fe₂VSi up to 193 K. These results are discussed in terms of the electronic structure in Fe₂VSi.

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  We have investigated magnetotransport properties of magnetic tunnel junctions (MTJ) with rock-salt type ZnO(001) or MgO/ZnO(001) barriers by both calculation and experiments. The first-principles transmission calculations based on NEGF method clarifed that the MgO/ZnO barrier had coherent tunneling through Δ₁ state such as a conventional MgO(001) barrier. Experimental results revealed that the MTJs with an MgO/ZnO barrier had an MR ratio of 70% at a low resistance-area(RA) product of 0.5Ωμm². This MR ratio is almost the same as the MgO barrier or higher. The rock-salt type ZnO(001)-based MTJs seem to be suitable for application to the read magnetic heads of hard-disk drives (HDDs) with an areal recording density of over 500Gbits/in².

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  We investigated the epitaxial growth of high-quality Fe₃Si thin films on Si(111) and demonstrated electrical injection and detection of spin-polarized electrons in Si through the Fe₃Si/Si Schottky-tunnel contacts. TEM observations and analyses of electron diffraction patterns revealed that precisely controlling the Fe/Si ratio during growth is important to obtain well ordered Fe₃Si structures and atomically abrupt heterointerfaces at the same time. The electrical properties of Fe₃Si/Si Schottky diodes with various carrier concentrations were also examined, and highly transparent tunnel contacts were demonstrated. We were able to clearly detect nonlocal spin signals in Si at 150K using Fe₃Si/Si lateral four-probe devices.

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  We numerically investigated current-induced dynamical phases of a geometrically constrained magnetic wall (GCMW) confined in a magnetic nano-scale contact. We clarified that the dynamical phase depend on the value of current j and there exist three dynamical phases which are separated by two threshold currents of j_c1 and j_c2. For j < j_c1, we confirmed that the GCMW is deconfined from the contact because of the current induced displacement of the GCMW. On the other hand, we found that the GCMW is confined in the contact for j_c1 < j < j_c2. For j > j_c2, we also found an oscillation where nucleation and annihilation of a magnetic domain are alternately repeated.

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  The magnetic coupling between TbFeCo and FeCo in perpendicular MTJs with RE-TM alloy films was investigated. Two specimens that had different crystalline orientations of FeCo were prepared. The first was TbFeCo/FeCo(001)/Ta, and the second was TbFeCo/FeCo(110)/Ta, and their magnetic properties were observed. We confirmed that the squareness ratio of specimens with FeCo(001) was about 9% higher than that of specimens with FeCo(110). In addition, the lattice constants of FeCo(001) films were observed, and we confirmed that FeCo lattices needed to be stretched perpendicularly to obtain appropriate squareness in perpendicular magnetic properties.

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  Current-induced domain wall motion in TbFeCo wire with perpendicular magnetic anisotropy has been directly observed by Kerr microscope. The moving direction of domain wall is opposite to the current direction, which is in agreement with the spin torque transfer theory. The critical current density in ferrimagnetic TbFeCo was found to be only 5.4×10⁶ A/cm², which is at least 1 order smaller than in other metallic materials reported so far.

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  The inverse spin-Hall effect, i.e., conversion spin currents into electromotive force, has been investigated in Pt_1-xM_x(M=Cu, Au) thin films. We measured the electric voltage due to the inverse spin-Hall effect induced by spin pumping in Ni₈₁Fe₁₉/Pt_1-xM_x(M=Cu, Au) bilayer systems with changing x and the species of M. The experimental results revealed that the dependence of estimated spin-Hall angle θ_ISHE on longitudinal conductivity was well reproduced by θ_ISHE ∝ σ_xx^0.54, indicating that the spin-Hall angle in metallic films could be controlled by changing the species of impurity and concentration in the metallic films.

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  The strain sensor using inverse magnetostriction effect has very high sensitivity with strain. In oreder to improve the sensitivity, the study on the energy behavior of the strain sensor is very important. Therefore we fabricated the sensor with magnetostrictive film and tried to examine the relationships between magnetoelastic energy and anisotropy energy in this study. In particular, we focused on the magnetic domain change by magnetoelastic energy and Zeeman energy. Moreover, we examined impedance property of the strain sensor applied strain and magnetic property with strain. As a result, using magnetic domain change observation, we could observe the anisotropy energy change by applied magnetoelastic energy and discuss the relationships between magnetoelastic energy and anisotropy energy.

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  A new structure for a rotation sensor using magnetic wires is proposed. The sensor consists of magnetic wires attached directly to a rotating shaft. A pick-up coil and exciting magnets are separately located outside of the rotor. This sensor structure and configuration offers advantages over the conventional structure, whose pick-up coil iswound around a magnetic wire. The location of the pick-up coil and magnets in the proposed method was optimized. It was found that multiple output pulses could be obtained for every turn of the rotating shaft simply by placing corresponding numbers of wires on the shaft. The implementation of this sensor in an electrical vehicle was examined, and an output pulse voltage with an S/N ratio sufficiently high for practical use was observed.

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  In this paper, we present a new method of building a fundamental orthogonal fluxgate magnetometer by using a simple switched capacitor phase-sensitive detector (PSD), in order to accomplish low power consumption and miniaturization. A PSD is one of the most important components of the fluxgate magnetometer electronics. We made a switched capacitor PSD with an LT1043 IC which has a dual switched-capacitor building block, and built it into the fluxgate magnetometer electronics. We also constructed a sensor head with an amorphous wire. Experimental results show that the power consumption of the proposed method is as low as 75 mW with a power supply of ±3 V, and the resolution of the sensor is 27 pT/√Hz. The proposed method uses only three small-scale ICs, which enable us to miniaturize the flux magnetometers.

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  This paper discusses the possibility of realizing improvements in magnetic properties of non-oriented electrical steel sheets. In such sheets, a random {100} texture can increase flux densities and decrease iron losses, and the increase in flux density at 5000 A/m (B₅₀) may be over 0.2 T, while decrease ratio of iron loss at 1.5 T and 50Hz (W_15/50) may be more than 1/3. On the other hand, the improvement of iron loss at 1 T and 400Hz (W_10/400) due to a random {100} texture may be little, but the texture can increase flux densities, and the increase in flux density at 800 A/m (B₈),where motors are designed, may over 0.4 T. It is important to improve metallurgy and rolling technology in manufacturing process in order to realize the theoretical optimum magnetic properties of non-oriented electrical steel sheets.

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  Axial-gap motors have higher torque density than those with conventional radial gaps because they are able to reduce the thickness of the motor and increase the number of poles with a relatively smaller radius. Therefore, axial-gap motors are expected to be applied to various fields such as home electrical appliances and the in-wheel motors for electric vehicles. The establishment of an optimal method of design for axial-gap motors is required, but it generally takes a long time to calculate the characteristics of these motors since it is necessary to analyze the three-dimensional electromagnetic field. To overcome this problem, this paper presents a method of calculating the characteristics of axial-gap motors with skew based on reluctance network analysis (RNA). The validity of the proposed method is tested and proved by comparing the measurements with the results from finite element method (FEM) analysis.

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  We investigated the improvement in characteristics of a capacitor motor wedged with soft ferrite materials to conserve the electrical energy consumed by induction motors. However, a method of estimating the loss in a capacitor motor is necessary to obtain an optimum design for a motor with magnetic wedges. Consequently, we propose a reluctance network analytical (RNA) model that we used to estimate the loss in the capacitor motor. The no-load characteristics, load characteristics, and characteristics with the locked rotor were calculated based on the RNA model, and we estimated the equivalent winding resistance of the rotor for the equivalent circuit model of a capacitor motor.

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  Mn-Zn ferrite cores are used for DC-DC converters under the excitation conditions of frequencies ranging from tens of kilohertz to several megahertz. The development of a mathematical model enabling the power loss of Mn-Zn ferrites to be estimated in high-frequency regions, should contribute to improving the design of the converters. The spatial network method (SNM) has been used to analyze the electro-magnetic field of electric machines and applied to obtain the power loss in ferrites whose properties have been treated as linear. This paper presents the SNM including ferrite’s non-linear magnetic properties, which are magnetic saturation, hysteresis and dynamic magnetic losses. In addition, the dielectric features of Mn-Zn ferrite are taken into account. The simulated results are closely in accordance with the experimental values and demonstrate dimensional resonance caused by high-frequency excitations.

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  Permanent-magnet magnetic gears have various advantages such as having low acoustic noise and being maintenance-free in comparison with conventional mechanical gears. Various types of magnetic gears have been introduced in previous papers. Of these, planetary permanent-magnet magnetic gears have higher transmission torque than other types. We compared two types of planetary magnetic gears. The first utilized a surface permanent magnet (SPM), and the second used an interior permanent magnet (IPM). We compared the transmission torque and eddy-current loss that occurred in these magnets.

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  This paper discusses the basic characteristics of a double stator slot-type permanent magnet generator (DS-PMG). The PMG was basically operated in a single-phase and the flux direction in the air gap was radial. It was developed to optimize the magnetic flux linkage in a single-pole PMG. Simulation with the Finite Element Method (FEM) and calculations were used to analyze the PMG’s characteristics. In addition, the performance of the PMG prototype was evaluated to ensure the simulation results were accurate. The DS-PMG had a low Total Harmonic Distortion (THD) of 6% and high efficiency of 80% at the rated speed of 3000 rpm. Here, THD is a comparison of the fundamental waveform to its harmonic content. Its output power was three times that of the single PMG.

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  The practical use of a single-phase motor having a three-phase rotating field is very useful for energy conservation. We have been studying a single-phase input three-phase parametric motor and have succeeded in generating a three-phase rotating magnetic field in the stator. However, the mechanism for generating three-phase voltage has not yet been clarified. This paper discusses the factors that cause three-phase voltage based on the excitation voltage dependence of state of parametric oscillation and the change of the frequency of parametric oscillation voltage.

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  This paper describes a new formulation to the three-dimensional movable magnetic levitation system using I-shaped electromagnets and a lower dimensional technique at a suitable selected operating point. In the formulation, an attractive force per unit was first derived to assume that an I-shaped electromagnet and a floating object were present as a magnetic charge model. Then, the resulting force vector was determined on the geometric configuration of I-shaped electromagnets. Model-following servo controllers designed for each state equation in the x^-, y^-, and z^- directions, which were derived from the proposed formulation and lower-dimensional technique, successfully stabilized the maglev system.

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  Air core coils are widely used in induction cooking appliances and transformers. To improve their efficiency, two characteristics are required: high combination and low loss. We propose that a litz wire using magnetoplated wires (MPWs) be used as the conductor material of a coil. Theoretical expressions for the ac resistances due to the skin and the proximity effects of air core coils using copper wires (COWs) and MPWs are derived. The calculation errors of the ac resistances of air core transformers using COWs and MPWs in the frequency range from 100 kHz to 1 MHz are 10% and 22%, respectively. The resistances of air core coils using COWs and MPWs at a frequency of 1 MHz are 43.2 mΩ and 29.2 mΩ, respectively, 34% less than of conventional air core coils.

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  This paper compares double-stator slot-less-type topologies for a permanent magnet generator (PMG), focusing on the characteristics of the PMG with differently shaped permanent magnets (PMs) and pole types. A comparison is made between an arc-shaped PM and a rectangular-shaped PM. In addition, the effects of a single-pole PM and multiple-pole PM are investigated. According to the results obtained by using the finite element method (FEM), the generated power of both types of PMG is almost the same when all parameters are fixed except the PM shape and pole type. However, the double-stator slot-less PMG with a rectangular shaped multiple-pole PM is superior in terms of PMG weight and cost. The results are verified by comparing the calculation, simulation, and measurement results for a prototype of the PMG.

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  In-wheel direct-drive motors are directly connected to the wheels of electric vehicles. They therefore reduce mechanical loss in gears, achieve a high degree of control, and make efficient use of a car’s interior space. However, the volume of the motor to be a placed in the wheel is limited. Therefore, high torque density is required. A dual-rotor structure to arrange the rotor inside and outside the stator to improve the torque density of the permanent magnet motor has recently been proposed. However, few evaluations of Switched Reluctance (SR) motors have been done. We therefore assessed a dual rotor SR motor taking support from the stator into consideration. We considered the shape of the stator in supporting this dual rotor SR motor.

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  We earlier proposed a planar parametric transformer using a laminated Si-Fe core. In our study, we noticed the Mathieu equation represented the stable state or unstable state of a parametric oscillation. In this paper, (1) the Mathieu equation is obtained for the no-load condition and the load condition, and (2) the relationship between the stable state or unstable state of a parametric oscillation and the operating point of the transformer is clarified. We analyzed these states of a transformer by using MATLAB.

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