In order to obtain a ferromagnetic Mn-Al film with a single τ-phase, sputtering conditions such as the argon pressure, the composition of target, and the annealing temperature were investigated systematically. Mn-Al film with a saturation magnetization of 82 emu/g was formed only by sputtering at about 10-Pa argon pressure and subsequent annealing at about 573 K. The intensity of the magnetization was nearly the same as that of a bulk sample.

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The effects of ion bombardment during deposition on the structures and magnetic properties of Fe films were investigated by a bias-sputtering technique. In order to control the energy of incident ions at low bias voltages, a gas-flow-sputtering method was used in which effective deposition of films was possible even at 1-Torr pressure. Some marked influences on the grain structure and coercive force H_c of polycrystalline films were observed at bias voltages higher than -20V. The growth of crystal grains was promoted at low bias voltages in the range of -30V. In contrast, the crystallinity of films was suppressed at voltages around -100 V. The value of H_c was decreased by applying a substrate bias, and had a minimum value of 4 Oe when the bias was about -30 V. It was also observed that the oxygen content in films was decreased by bias-sputtering, as has been generally observed.

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Fe (001) single-crystal films were deposited on GaAs (001) substrate by the sputter-beam method. The films were characterized by X-ray diffraction, torque measurement, and magnetic measurements. Single-crystal Fe (001) films grow at substrate temperatures of 250∼300°C, with Δθ50 as small as that of the GaAs substratre. The H_c values of the films are about the same as those of Fe(001) films produced by MBE, which were reported previously.

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Changes in the magnetic properties of electrolessly plated CoP films were studied. The microstructures and/or compositions of the films changed when electrolysis was performed simultaneously with electroless plating. In particular, a decrease in coercivity and an increase in the saturation magnetization observed in a CoP film with a coercivity of 580 Oe were due to the appearance of Co-rich, flat grains of single crystals. The magnetic properties of CoP films are changed along with the microstructure upon electrolysis. Electrolysis performed simultaneously with electroless plating is, therefore, an effective method for controlling the magnetic properties of electrolessly plated thin films.

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The effect of interface characteristics on exchange coupling in Ni-Fe/Fe-Mn bilayer films has been discussed in order to explain the mechanism of exchange coupling. The condition of the interface was changed by Ar ion bombardment of the Ni-Fe surface before Fe-Mn deposition. The results showed that when the Ni-Fe surface was oxidized by exposure to the air before depositing the Fe-Mn, the exchange coupling could be observed only by removing the oxidized surface. Furthermore, when bilayer films were deposited without exposing the Ni-Fe surface to the air, the exchange coupling had a peak when the angle of Ar ion bombardment was about 30°. The results of STM observation and X-ray diffraction showed that the exchange coupling did not depend on the surface roughness of a Ni-Fe film, but depended on the X-ray intensity ratio of (200) to (111). Therefore we concluded that the preferred crystal orientation of Ni-Fe surface might affect the exchange coupling in Ni-Fe/Fe-Mn bilayer films.

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Oxide thin films of Ni_yZn_xFe_3-x-yO₄ (0≤x+y≤1.0) were prepared with high deposition rates of 200∼300nm/min by plasma-enhanced MOCVD from mixed gas containing Fe (C₅H₇O₂)3, Zn(C₅H₇O₂)2, Ni (C₅H₇O₂)2, and O₂, at a RF power≥400W and temperature=600°C under high flow-rate conditions of source vapors, such as 2.35×10^-5 mol/min for the Fe source. The XRD patterns of the films indicated that Zn_xFe_3-xO₄ (0≤x≤0.8), Ni_yFe_3-yO₄ (0≤y≤1.0) and Ni_0.4Zn_0.4Fe_2.2O₄ films consisted of only a spinel phase with good crystallinity. However, a small (111) peak of NiO was found with the spinel peaks in the XRD pattern of the Ni_0.8Zn_0.2Fe_2.0O₄ film. SEM images of the films showed that they had densely columnar structures, irrespective of their compositions.

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Fe₁₆N₂ films (with a thickness of 3000Å) were fabricated on MgO (001) substrates by the conventional DC facing targets sputtering method with a controlled reactive plasma, with an electron temperature of T_e=0.3eV, an electron density of N_e=1×10¹⁰cm^-3, a deposition rate of 200Å/min and an N₂ flow ratio ranged from 10% to 20%. In an as-deposited state, α′ single phases with various nitrogen contents were formed. After annealing at 150°C for 2 hours, an α″ phase (≅11 at%N) and an α′ phase (11.1 at%N and 1∼2 at%N) were formed. M_s showed nearly the same value as α-Fe (2.2T), despite the existence of the α″ phase. The lattice constant c in the α″ phase in the present films agreed well with the value reported by Jack; however, the values of the lattice constant a in the present films were about 1∼3% smaller than Jack’s value. The unit cell volumes in the α″ phase in the present films were 192.5∼202.6ų, about 1.4∼6.3% less than Jack’s value of 20.5ų.

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Co-(0∼15)at%Ta-N sputtered films were investigated in order to clarify the correlation among the structure, induced magnetic anisotropy, local anisotropy fluctuation, and soft magnetic properties. The results for electric resistivity and film magnetostriction indicate that the temperature T_x1 at which Co crystallites were formed from amorhous structure was lower than the temperature at which crystallites of Ta-nitride were formed, and the difference was about 150°C in Co-15at% Ta-N films. On the other hand, uniaxial magnetic anisotropy was drastically induced at T_x1 by annealing in the magnetic field, while, even after crystallization, a uniaxial anisotropy of about 2×10³ erg/cc could be reversibly induced by annealing in the magnetic field.

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Fe-N films were synthesized by means of ion beam deposition techniques. Nitrization was performed by using an assist gun during the sputtering of Fe films. As deposited Fe-N films composed of two phases, α-Fe and γ′-Fe₄N, had a large coercive force (H_c) of over 20 Oe. When the films were annealed in a vacuum, their H_c improved drastically, and had a minimum value of less than 1 Oe at 400°C. The films also had a high permeability of over 2000 as well as high resistivity (around 80 μΩcm) in spite of a high saturation magnetization (around 18 kG). The small grain size and stress relaxation in the films were closely related to the soft magnetic properties. The volume fraction of the γ′-Fe₄N phase also affected the decrease in H_c, because the anisotropy normal to the film plane was reduced by increasing the magnetostatic energy when the volume fraction was 0.5.

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In an effort to obtain a high-quality magnetic thin film for microinductors, the magnetic and structural properties of highly resistive Fe-BN films were observed. In the case of the films deposited on substrates electrically isolated from a chamber, B_s, resistivity, and H_c varied as functions of the sputtering gas pressure (P_s). The structures of as-deposited films were amorphous, and on annealing they crystallized into an α-Fe single phase. On the other hand, the above parameters were independent of P_s for films deposited with a negative bias voltage applied to their substrates. These films were also in anamorphous as-deposited state, and crystallized into Fe₃B and α-Fe on annealing. XPS analysis revealed that application of a negative bias voltage decreased the N and O content, especially the concentration of BN, in these films. This finding is attributed to the enhancement of Ar⁺ ion bombardment at the time of deposition.

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The effects of substrate bias on magnetic properties and structures were investigated for FeTaN films deposited by a new sputtering method. Films sputtered with an RF bias of less than 80 W exhibit good soft magnetic properties and have a fine-grained microstructure consisting of α-Fe and TaN. The direction of the in-plane magnetic anisotropy for the films changes with the bias applied to the substrate. For those prepared with an RF bias of more than 100 W, the soft magnetic properties deteriorate because of the change of the fine grain microstructure from bcc-Fe to fcc-γ′Fe₄N (Ta). Substrate bias-sputtered FeTaN/SiO₂ multilayered films were also prepared in which the anisotropy direction of each FeTaN layer was different from that of the adjacent FeTaN layer. The resultant multilayered films show isotropic high permeability and excellent frequency response, and are suitable for laminated-type head core materials.

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Fe-N films were deposited on glass substrates by rf sputtering with a mixture of Ar, He, and N₂ gases. The relationship between the properties of the films and the plasma species was investigated by the optical emission spectroscopy analysis. In the Ar+He+N₂ plasma, many N₂+ molecular ions were generated by He atoms in neutral excited metastable states through Penning ionization, and contributed to the reaction of Fe with nitrogen. Fe-N films prepared with a very low N₂ content of less than 0.03% exhibited a larger magnetization than α-Fe.

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Fe/Fe-N multilayered films were made by alternation of Fe sputtering at various Ar gas pressures and ECR nitrogen plasma exposure, and the structure and magnetic properties of these films were investigated. Growth of a columnar structure was observed in an Fe film prepared at a high Ar gas pressure. Fe/Fe-N multilayered films with an Fe layer prepared at a low Ar gas pressure have a low H_c and high B_s. X-ray diffraction suggests that the lattice spacing of Fe(110) and the compressive stress in these films increase with a decrease in Ar gas pressure. These structural changes are caused by the nitrogen diffusion from the Fe-N layer into the Fe layer. Nitrogen exists as a solid solution in an Fe layer prepared at a low Ar gas pressure, but as a nitride in an Fe layer prepared at a high Ar gas pressure.

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NiFeCo/Cu multilayers with NiFeCo buffer layers prepared by RF magnetron sputtering show the giant magnetoresistance (MR) effect with oscillations as a function of Cu thickness. At the second peak of the oscillation, the multilayers show an MR ratio of 12% in a field as low as 50 Oe. The structure and the MR properties are stable against annealing up to about 300°C. A field sensitivity of about 0.4%/Oe is obtained for the minor loop of the MR curve measured in a field along the hard axis. The fieid sensitivity is almost constant in the frequency range up to 1 MHz.

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Multjlayers of Cu/Co/Cu/NiFe prepared by evaporation in an ultrahigh vacuum showed induced ferrimagnetism and giant MR properties. The slope, the linear region of the MR profile at around zero field, is sensitive to the coercive force and squareness ratio of magnetization of the NiFe layers. The maximum slope was 0.41%/Oe for Cr(50Å) [Cu(50Å)-Co(10Å)-Cu(50Å)-NiFe(15Å)]×10. The annealing temperature dependence of the slope was due to the interdiffusion of NiFe and Cu layers. Improved thermal stability was realized by the use of thicker NiFe layers.

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Film structures of sputter-deposited Co/Cu multilayers depended strongly on preparation conditions Such as the Ar gas pressure (P_Ar) and the substrate bias voltage (V_B). For the films deposited at V_B=0V, the interfaces were flat and (111) plane orientation was good at low P_Ar (200) textured grains were also Observed for films with low P_Ar. The (111) orientation was better for -30-V films than for 0-V films. The interface was flat at high P_Ar, different from 0-V films. Giant magnetoresistance (GMR) depended strongly on the layer flatness, the density of the films, and the existence of crystal grains with fcc (200) texture. The effects of annealing on the film structures and the GMR were also investigated. Ten minutes‘ annealing at 200°C in a vacuum did not change the film structure very much, but the first GMR peak value of 0-V films decreased significantly, in contrast to the stable second GMR peak.

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Ni_8OFe₂₀/Cu multilayers were prepared on a glass substrate by magnetron sputtering. The dependence of the magnetoresistance on the thickness of the Cu layer, the thickness of the Ni-Fe layer, the thickness of the buffer layers for Fe, Ni₈₀Fe₂₀, Cu, and the number of bilayers was investigated. The MR ratio exhibited a peak at d_Cu=10Å, Where the MR ratio was about 20% at room temperature. When the thickness of the Ni₈₀Fe₂₀ layer was varied, the MR ratio exhibited a broad peak at d_Ni-Fe=15∼30Å. The interlayer exchange interaction is evaluated as about 3×10^-2 erg/cm², irrespective of the thickness of the buffer layer. The MR ratio increased with an increase in the number of bilayers N, and saturated when the total film thickness was about 800∼1000Å.

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Pt-Fe, Pt-Co, and Pt-NiCo alloys and multilayers were prepared on an SiO₂ Substrate by the DC magnetron sputtering method. The reflectivity spectra and magneto-optical Kerr spectra were measured in these specimens, and the diagonal and off-diagonal elements of conductivity tensor were deduced from them. The results of this work are as follows: (1) The peak energy position of magneto-optical Kerr rotation spectra showed a systematic shift to lower energies as the transition metal was varied from Fe to Ni, both in multilayers and alloys. (2) Simulation using the above-determined conductivity tensor of alloys revealed that alloy layers existed at the interface between Pt and transition metal layers in all the Pt-based multilayers investigated. (3) Obvious effects of plasma-enhancement were confirmed in the short-wavelength magneto-optical Kerr spectra in the Pt-based alloys.

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We have lnvestigated a double-structured fourlayered composite anisotropic film to obtain advanced properties for practical use. Its composition is {[CoNbZr(250 nm)/SiO₂ (20 nm)]₄/SiO₂(t)}₄ with a shift angle of 45°. The sample was annealed in a small rotating field. The total thickness of the metal layers is 4.0 μm With an optimum SiO₂ thickness. This film shows a flat frequency response and unchanging temperature dependence of the permeability. Thicker SiO₂ is recommended for applications. Furthermore, annealing from 200°C to 400°C resulted in high permeability of 1000∼2000 and an excellent frequency response of μ′ at 1∼100 MHz in all directions on its plane. These results may be explained by the magnetic interactions of CoNbZr magnetic layers, which are in close contact with one another across intervening SiO₂ layers.

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The soft magnetic properties of Fe_100-xCo_x (x=30 and 4) multilayers (MLs) prepared by the RFmagnetron sputtering method are reported. The growth of FeCo crystallites is suppressed by the presence of Zr interlayers, and the layer structure is stable up to 500°C. The annealing behavior of the coercivity and permeability is discussed in relation to the magnetostriction and magnetocrystalline anisotropy of FeCo crystallites.

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The magnetic and structural properties of multilayered CoBN/AIN films prepared by sputtering Were investigated, With the intention of creating suitable films for application to micromagnetic devices operating at high frequency. A CoBN single layered film has ρ of about 340μΩcm, Bs of about 10.3kG, and perpendicular magnetic anisotropy. CoBN/AIN multilayers, even where the thickness of the AIN layer is around 3Å, exhibit soft magnetic properties (H_c<1 Oe and μ>500) in a wide range of combinations of film thicknesses of both layers. SEM observation suggests that the soft magnetic properties of the multilayers originate in their in-plane uniaxial anisotropy and fine grains in the CoBN. The magnetostriction of multilayers ranges between-1 and +1×10^-6, and their anisotropic field is over 15 Oe. Although the film thickness exceeded 2μm, μ was maintained, even at a frequency close to 300MHz.

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Various types of clamp-on current sensor have long been in use, because they are so easy to handle. Recently, power instruments such as inverters have become widely used and clamp-on sensors have been adopted in industry. Current sensors should have the high-performance characteristics of a wide frequency band, a wide measuring range, and high accuracy.
In this paper, We use FEM to calculate magnetic flux of an ac/dc zero-flux current sensor equipped with a Hall element, and analyze the operational mechanism. The analytical results agree well with experimental data. The clamp-on current sensor that we developed has a wide operating range of frequency from dc to 1 MHz, as well as high accuracy of with in ±0.5%.

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An amorphous alloy layer prepared by the laser-quenching technique was applied to a magnetostrictive torque sensor. Fe₇₈B₁₃Si₉ amorphous alloy layers Were Produced on stainless steel substrates by laserquenching. The laser-quenched layers consisted of a mainly amorphous phase, partially including the crystallized heat-affected zones. VSM measurement showed that the amorphous alloy layers have magnetic easy direction along the laser scan. Taking account of this magnetic anisotropy, we prepared a torque sensor by scanning the laser beam on the surface of the shaft at 45° to the shaft axis. The torque sensor thus prepared exhibited sufficient sensitivity and good linearity in detecting static torque.

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The magnetic anisotropy sensor (MAS) is a stress sensor that detects internal stresses induced by the inverse magnetostrictive effect. In this study, the sample is a cold rolled steel plate used for a car body. Because the penetration depth of flux is greater than the thickness of the sample, 0.75 [mm], the MAS detects the average of the internal stress distribution Therefore, the output voltage is affected by the internal stress distribution. The flux density distribution in the sample caused by the skin effect is varied with the excitation frequency. This paper shows that the internal stress distribution can be estimated from the output voltage-excitation frequency characteristics.

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We previously constructed an accurate magnetdisplacement sensor for detection of eyelid movement, using an amorphous magnetic core multivibrator. However, some improvements in the eyelid movement sensor are necessary in order to achieve independence of the magnetization direction of the cores and a wider sight space. We therefore constructed another accurate magnet-displacement sensor for detection of eyelid movement, this time, using amorphous wire magnetoinductive (or MI) elements. The elements were formed by using tension annealed zeromagnetostrictive amorphous wires. The MI effect and the symmetrical MI characteristics of the elements are used to form thinner sensor heads having no coils and to change their inductances independent of the magnetization directions.

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A distance sensor that uses a large Barkhausen effect in amorphous wires magnetized by a current is described. Helical anisotropy is created in an Fe_77.5Si_7.5B₁₅ amorphous wire (cold-drawn and then tension-annealed) by applying torsion,and consequently the wire can be magnetized by the circumferential magnetic field created by the wire current. This type of distance sensor does not need a long exciting solenoid coil, and its construction is simple. The characteristics of the sensor are controlled by the number of the applied torsion. The smallest deviation from the linearity δ=0.4%/FS for a 1000mm-long wire was obtained when the value of the torsion was 10 turns/m. Domain wall motion in a twisted amorphous wire is also analyzed. The domain wall velocity increases linearly with the wire current, and its mobility decrease with increasing torsion.

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This paper describes the preparation of ferrite thick film (FTF) and its application to pressure/photo sensors. The FTF is composed of ferrite powder with various possible Curie temperatures, polymers, and solvents. The mixed magnetic semiconductor fluid was dried up at 120°C after printing on a plastic substrate. The pressure sensor is constructed by using the high-Curie temperature FTF and a pressure-sensitive element. The FTF converts pressure into reluctance, Whose minute changes are read out by a Hall element. When a photo sensing PFTF, Which is a device painted the radiant flux absorbent On the surface of the low-Curie-temperature FTF, sucks in the light energy, the PFTF reluctance increases, and thus light-magnetic conversion is made. Therefore, the FTF can be used for measurements of pressure, position, fluid flow, and luminous flux.

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The magneto-inductive effect (MI-effect, for short) is a phenomenon that changes the inductance L for an external field H_ex in a ferromagnetic wire element magnetized by application of a wire ac current I_ac. When I_ac is applied through a ferromagnetic wire, the voltage e_tot is induced between both ends of the wire. The voltage has two components: a voltage e_R of R_wI_ac (R_w is the electric resistance of the wire) and a voltage e_L of dφ_θ/dt (φ_θ is a circumferential flux in the cross-section of the wire). e_L is detected by subtracting e_R from e_tot,using a simple resistor circuit. The amplitude |e_L| of e_L decreases with increase in |H_ex| caused by the decrease in L. That is, e_L is an amplitude-modulated wave with |H_ex|. The waveform of |H_ex| is detected by using a simple demodulator with a diode and capacitor. A sensitive MI element is created by using a slightly negative magnetostrictive amorphous wire having a length of 2 mm and a diameter of 50-μm Without any coils. This MI element is expected to have applications in new sensitive magnetic heads for accurate rotary encoders, hard disks, and various magnetic cards.

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By using the magnetic lithography technique previously reported, an optical grating can be easily formed not only on a plane, but also on a convex or concave surface. since the optical characteristics of this relief-type grating depend on its cross-sectional shape, it is important to investigate the factors determining the shape of the grating in magnetic lithography so that this technology can be applied to an encoder plate. In order to improve the encoder's performance, it is necessary to control the crosssectional shape of the grating and to try to produce a grating that has no Fraunhofer zeroth-order diffraction light spot by means of magnetic lithography. Results show that the characteristics of the gratings have good repeatability in production. Conditions for developement of such gratings are investigated.

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The operating characteristics of parametric transformers and dc-ac converters with an orthogonal core greatly depend on the core shapes. Accordingly, in the optimal design for the applications, we used to clarify the quantitative relationship between the orthogonal-core shape and the operating characteristics of the application devices. In this paper, the application characteristics in terms of the orthogonal-core shape are discussed analytically with reference to a magnetic circuit model of the orthogonal core.

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In this paper, We describe a numerical model of a bridge-connected magnetic circuit for use in SPICE. The model was devised on the basis of a bridge-connected magnetic circuit with saturation and hysteresis effects. As an example of the application of its SPICE model, We analyzed the transient behavior of the power-measuring circuit caused by the principle of magnetic oscillation, using a bridge-connected magnetic circuit and a saturable core. The calculated results agree well with the measured ones. A SPICE model of the bridge-connected magnetic ciruit presented here is useful for the analysis and design optimization of the power-measuring circuit.

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A ferroresonant-based two-phase circuit has a function of parametric oscillator, and is widely used in various kinds of power device. When the load conductance of the circuit is very small, the parametric oscillations occurring in the circuit become unstable. It has been reported that the occurrence of unstable oscillations is due to the resistance of the power supply side of the circuit. When the magnetization curve of the circuit reactor has a sharp saturation characteristic, unstable oscillations that are different from the above-mentioned type occur in the first ciruit of the two-phase circuit. This paper clarifies the relationship between the unstable state of the circuit and the nonlinearity of the magnetization curves of the cores used in the circuit, and confirms experimentally validity of the analysis.

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The frequency-dividing-type three-phase inverter, Which consists of a single-phase square wave inverter and a three-phase ferro-resonant circuit, has excellent efficiency, constant-voltage characteristics, and three-phase balance. These advantages make it suitable for use as a DC-AC converter and a UPS. However, When this three-phase inverter is used as a UPS, a start-up circuit with a complicated sequence is needed to reduce the capacity of the single-phase inverter. If the sequence is simplified, the phase sequence of the voltage cannot be determined, Which creates another problem. In this paper, the relationship between circuit imbalance and the phase sequence of three-phase voltage is reviewed through experiment and analysis. In consequence, the relationship between circuit imbalance and phase sequence is clarified. The results given in this paper provide useful information on circuit constants that can reduce costs by simplifying the start-up circuit of a frequency-dividing-type.

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This paper compares the performance of a linear pulse motor (LPM) and a linear electromagnetic solenoid (LES) when used in a total artificial heart. Our experiences with LPM-driven total artificial hearts have shown that the following problems need to be solved:
1. Long-term reliability of the linear bearings
2. Low thrust of the LPM.
From another technical point of view, these problems concerning the LPM may be solved by using an LES instead. We therefore designed an LES for a total artificial heart, using the finite element method (FEM) for calculation. Comparison of th performance of the total artificial hearts using the LPM and the LES allowed us to reach the following conclusions:
1. The newly designed LES heart has a thrust/ volume ratio four times larger than that of the LPM heart.
2. The LES heart has a longer life than the LPM heart, because there is little friction.

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The Linear Proportional Solenoid (LPS) is an actuator for a proportional control valve used in hydraulic pressure-control devices. The LPS has the basic characteristics that the thrust must be constant in the designated displacement range and must also increase in proportion to the exciting current. This paper deals with the effect of using dither to remove hysteresis phenomena, and numerical solutions of the thrust, F, the displacement, x, Which are characteristics of the LPS. Dither is a useful oscillation of small amplitude, introduced to overcome the effect of hysteresis. When dither is applied, the maximum hysteresis of the thrust is decreased from 6% to 3%. The LPS consists of four different magnetic materials, and its F-x characteristic was calculated by means of the Finite Element Method (FEM). The calculated value of the F-x characteristics approximates the measured value within an error of 2%. A new proposal for the LPS, Which will give it a wider range of thrust constant, is also described in this paper.

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A linear dc motor (LDM) is useful in a high-speed and high-accuracy positioning system with a feedback controller.¹⁾ A moving-coil-type LDM can be used for a pen recorder. We analyzed the magnetic field of an LDM, using a 3D finite element method, and designed an improved LDM with the specific intention of increasing the flux density in the gap. The mechanical time constant is the most basic parameter in a positioning control system. We calculated the mechanical time constants of the LDM at various frequencies, and clarified the effect on the mechanical time constants of increasing the flux den sity in the gap of the improved LDM.

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The structure and operation of the four-legged linear parametric motor have excellent features in that the structure is very simple and the operating maintenance is negligible.
We calculated the performance characteristics of the linear motor numerically, using a twodimensional static field analysis program, and obtained the flux-density distribution in the gap. Further, We show that the performance characteristics of the four-legged linear parametric motor can be improved by decreasing the thickness at the center of the common magnetic circuit.

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A parametric motor has numerous attractive features not found in ordinary motors, such as over-load protection, Simple construction, low cost, and low noise. This paper discusses the mechanism of iron loss occurring in the core of a parametric motor, with a view to further improving the motor's characteristics and putting it to practical use. It is shown that a greater part of the iron loss in the motor occurs in the common magnetic circuit, and is caused by an alternating magnetic flux along a direction perpendicular to the plane of the lamination. It is also shown that the eddy current loss occurring in the common magnetic circuit when the common magnetic circuit is radially excited is closely related to the magnetization process due to the domain wall displacement.

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This paper deals with a method for determining complex permeability in hysteresis motor analysis. The method assumes that magnetic intensity distribution is sinusoidal in the direction of rotation. Analysis of a hysteresis motor on asynchronous speed is then performed on cylindrical coordinates with modified Bessel functions. The results of calculation agree well with the experimental results, confirming the effectiveness of the proposed method of determining complex permeability, and of the proposed model.

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The “Cordless Power Station” is a power supply system without a cord. The system makes use of electromagnetic induction generated with coils. This system will have uses such as supplying power to portable household electric appliances or charging circuit systems for batteries. We studied the powertransmitting characteristics and the structure of the Cordless Power Station. We also measured the distribution of the magnetic flux density around the coils and discussed the effects of using amorphous fiber.

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This paper reports the design of a magnetic multilayer film with high permeability and low loss in the 1 MHz-1 GHz frequency range. The thickness of each layer and the magnetic anisotropy were optimized with respect to eddy-current loss and ferromagnetic resonance in the magnetic layers and dielectric break-down in the nonmagnetic insulator layers. A limit law that stands up between the permeability μ′_r(0) and the cut-off frequency f_c was analyzed, and the limit μ′_r(0)×f_c was expected to have a much higher value than Snoek's limit. The constant μ′_r of 300 in the range of 1 MHz-1GHz was achieved in an optimized CoZrNb/SiO₂ multilayer film.

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We derived an equivalent circuit for a figure-ofeight coil-type permeance meter in order to analyze its LC resonance characteristics. The equivalent circuit for the pickup coils was derived by using the same analysis techniques as for thin-film inductors. The driving sheets and twisted lead wires were modeled according to the theory of distributed constant networks. We made a permeance meter, measured the frequency characteristics of the impedance for the coils, and demonstrated the validity of the equivalent circuit. After describing the above steps, we discuss the LC resonance caused by the stray capacitance between the pickup coils and the driving sheets.

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A method of measuring the permeability of soft magnetic films at high frequencies was investigated. The main components of this system are a network analyzer and a parallel line. We attempted to discover why the value of the given permeability by the parallel line method is less than that given by the coil impedance method. As a result, we found that the leakage of field energy outside the line must be considered in evaluating the correct permeability. The parameter a was introduced for the leakage of the field energy. We then measured the value of the permeability by the parallel line method (10 MHz∼500 MHz), and this value matched well with that measured by using a figure-of-eight permeameter (1 MHz∼100 MHz). The dimensions of the parallel line were 15 mm in length, 11.3 mm in width and 1.5 mm in depth.

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This paper describes the high-frequency characteristics of a multilayered planar transformer consisting of two planar coils and Co-Fe amorphous magnetic films. The calculated values of the transformer operations, obtained by using a finite element method (FEM), are compared with the measured values. The analysis show that characteristic evaluation is useful for a simple understanding of the operations of the transformer. For a precise analysis, the resonance in the windings must be considered. The application of the transformer to a resonance-type switching converter is also discussed. A high efficiency of 49.5 % is obtained for a switching frequency of 6 MHz.

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This paper discusses the application of thin-film inductors to thin-film-based LC filters. We fabricated a monolithic thin-film LC filter by using the rf sputtering and dry-etching techniques. The filter consists of thin-film inductors and thin-fillm capacitors made on a common substrate. This filter was designed as a second-order low-pass filter having Chebyshev characteristics, with a cut-off frequency of 50 MHz. We developed a technique for measuring this two-port device at high frequencies, and then measured the frequency characteristics. Here, we discuss the merits of thin-film LC filters using soft magnetic thin films.

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This paper deals with the maximum quality factor with regard to the dimensions of an inner-coil type thin-film inductor with a closed magnetic circuit. We used an equivalent circuit, taking account of flux distribution and eddy current in the magnetic film and stray capacitances. The proposed inductor can give the maximum quality factor, Q_max=32, at f=20 MHz. The quality factor is mainly determined by the iron loss in the magnetic film.

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In this paper, a new type of strip-like magnetic core is proposed. The structure of this core is prepared by separating the nearest-neighbor strip, Which is made of SiO₂, by a gap (d), and then sputtering a magnetic film under an external field applied in a perpendicular to the exciting direction. The width of the strip lines(W_s)varied from 10∼1000μm. The arrangement of these high-density strip lines is confirmed by the domain structure and the frequency dependence of permeability. When the gap is greater than the thickness of the magnetic film, the magnetic domains are independent of each other, and the initial permeability is the same as that of the strip line film which is separated by space. When the strip width is decreased, the domain width decreases and the number of domains increases. The strip-like magnetic core is used in a thin film inductor. The inductance at 20 MHz and the maximum value of quality factor (Q_max) in the experimental inductor show maxima at about W_s=300∼500μm. This magnetic core is useful for increasing the inductance and quality factor of thin-film inductors.

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A phase memory logic module (PML module, for Short) was constructed, based on a high temperature superconducting core magnetic multivibrator. The phase logic is decided by the majority of multi-input, therefore the same as Parametron logic, and this module has applications in the field of neural network systems. However, the frequencies of oscillation f_osc of those PML modules are not exactly the same. Therefore, in this paper, We investigate ways of controling f_osc caused by the the frequency drawing effect. By using magnetic interaction between two coils of different modules, the frequencies of two modules f₁ and f₂ Can be drawn into the same frequency f_d. ln this case, the value of f_d depends on the phase differences among the oscillations of modules, and is not unique. If a common reference ac current with frequency f₀ is applied through coils to each module, f₁ and f₂ can be drawn into same frequency f₀. These frequency drawning effects were analyzed on the basis of the Royer's equation for the mutual inductance of coil.

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We carried out frequency analyses of cloth inductors and thin-film inductors using an amorphous core, both of which were applied to a micro dc-dc converter. As these inductors are used in highfrequency bands such as l∼100MHz, the frequency dependence of the inductance L, capacitance C and resistance R in the inductors cannot be disregarded. The undetermined coefficients obtained by a least squares method were determined by expressing L, C and R in terms of the coefficient of the exponent in regard to frequency. To examine the coefficient of the first and second power of the frequency, the hysteresis loss can be distinguished from the eddy current loss in the inductors. Moreover, the difference between the iron loss and the copper loss can be clarified. The maximum value of the quality factor is acquired at a frequency such that the iron loss is equal to the copper loss. The results calculated by this procedure are in approximate agreement with experimental values.

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The characteristics of microtransformers are estimated by the FEM. A microtransformer consists of a multilayered core and a conductor-embedded core. The dependence of both the inductance and the equivalent resistance of the core on the size is discussed, and the relationship between the magnetic properties and the transformer characteristics is also considered. For a small transformer, high permeability of the core results in high efficiency, and for a large transformer, a high resistivity has the same effect.

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