We developed a new single pole head without auxiliary pole for perpendicular magnetic recording. This head is called WSP head (W-shaped Single Pole head) because the head has a W-shaped side core which increases the recording and reproducing sensitivity. The recording and reproducing sensitivity of WSP head is the same as or higher than that of a ringtype video head. The side core consists of two parts. One is the part which surrounds the main pole. The other is the part for the return path of magnetic flux.
The effect of the return path was evaluated by computer simulation. The results indicate that the recording and reproducing sensitivity of the WSP head is higher than that of a single pole head without the part for the return path. It is shown also that the distribution of the perpendicular component of the magnetic field of the WSP head is governed by the main pole and is not disturbed by the W-shaped side core because the W-shaped side core is located sufficiently apart from the recording medium.
The effect of the length and the thickness of the main pole for the recording and reproducing characteristics was studied experimentally. We found that it is important to shorten the length of the main pole in order to improve the recording and reproducingcharacteristics.

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Single layer Co-Cr and double layer Co-Cr/Ni-Fe film of perpendicular recording material were prepared by magnetron DC sputtering from alloy target (19∼20wt%Cr) on PET film.
The coercive force perpendicular to the surface of single layer Co-Cr film was determined by means of the magneto-optical polar Kerr effect and compared with the volume coercive force measured by a vibrating sample magnetometer.
The surface coercive force agreed with the volume coercive force for over all single layer films from 0.18μm to 0.48μm thickness.
The comparison of perpendicular surface coercive forces between single layer Co-Cr and Co-Cr layer of double Co-Cr/Ni-Fe films was carried out. The result shows that the perpendicular surface coercive force in double layer was greater than that of single layer.
From SEM studies it was found that these properties may be attributed to the development of columnar structure inside the crystal grains, caused by enhanced heating effect of substrate in virtue of presence Ni-Fe layer in double layer film.
The dependence of surface coercive force upon the direction of film thickness in single and double layer film was also studied in relation to Auger analysis. Except for near the surface in double layer film, the surface coercive force was almost constant.

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Ferrite thin films have been prepared for use as high density magnetic recording tapes. Their recording characteristics as well as mechanical properties were evaluated. Ferrite thin film tapes were prepared by direct Fe₃O₄ sputter deposition on heat-resistant flexible base films, followed by heat-treatment. Internal stress in the ferrite thin film depends upon sputtering pressure and power. Excellent magnetic properties applicable to high density recording media, were obtained. After the oxidation, R_max≤0.03μm film surface roughness was attained.
Lubricated ferrite thin film tapes have excellent corrosion resistivity and sufficient low friction coefficient. High recording dencity, D_6dB of 50 K-FRPI, was obtained. The ferrite thin film tapes feature low noise and high C/N(≥41 dB). Experiments on color picture recordings were performed using a home VTR.

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The magnetization processes at the small area of the thin films and of the thin film heads have been studied by using the micro-Kerr effect method. The domain wall position be observed by the change of the polarity of the cross field magnetization curves in the rotational magnetization process. The equi-coercive force curves are the domain wall positions in the domain wall movement process. The magnetization processes for the upper magnetic yokes of the thin film heads were measured with this method.

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Physical properties of ion-beam sputtered Co-Zr amorphous alloy films up to 5 μm thick have been investigated by changing the substrate temperature.
It was found that the crystalline to amorphous transformation mode depends on the substrate temperature. When the substrate temperature is lowered, the crystalline to amorphous transformation range becomes narrow and higher resistivity amorphous films can be obtained with lower Zr content. For example, amorphous films with over 80μΩcm resistivity were obtained for more than 6 at% Zr content when the substrates were water-cooled. Films on the liquid-nitrogen-cooled substrate with even less than 5 at% Zr content were found to be amorphous and to have higher resistivity than those on the water-cooled substrate. On the other hand, RF sputtered Co-Zr amorphous films have lower resistivity and wider transformation range, compared with ion-beam sputtered films. This is because of the higher substrate temperature.
Co-Zr amorphous alloy films with over 5000 permeability at 10MHz and with more than 12 kG saturation magnetization were obtained by ion-beam sputtering. This is due to the less Zr content and higher resistivity of ion-beam sputtered amorphous films.

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Using a Finite Element Method (FEM), a comparative investigation has been made to obtain the fundamental characteristics under a dynamic magnetic field of a metal head for use in a 8 mm VTR as a ferrite head. The FEM process includes the calculation procedures for magnetic saturation and eddy current.
As a result of the investigations, we found that: (1) the materials of higher saturation flux density are superior to the materials of lower one in producing stronger magnetic fields at a high recording density, in spite of eddy currents which were present; (2) the transmitting efficiency of the magnetic flux is constant, regardless of manetic motive force, permeability, and ferrite or metal; (3) the inductance of a VTR metal head is independent of the head gap depth in the video frequency range due to the presence of eddy currents.

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This paper describes a new multiple-channel head and a scanning method using the head in the magnetic printer.
The head records spaced multiple lines each rotation of the magnetic drum and moves along the axial direction of the drum.
The head has multiple channels with different track widths.
The track widths of the preceding channels are wider than those of the succeeding channels. The latent images of the preceding channels are partly overlapped by the succeeding channels, whereby a high quality copy having a solid black is realized. A formula is presented which determines the track pitch of the head according to the number of channels and the scanning pitch.
From experiments we found that the track width of the last succeeding channel should be set to be about 10 micrometers narrower than the desired toner image width.

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Readout process of perpendicular magnetic recording is studied theoretically for the following three combinations: (a) A ring head and a single layer medium. (b) A single pole head and a double layer medium. (c) A ring head and a double layer medium.
First, the formulations of the readout processes of the three combinations are established for the sinusoidal recorded magnetization on the basis of the reciprocal principle.
Next, the following results are shown: (1) The phase of the readout voltage of the combination (b) is different by ninety degrees from the phase of the combination (a) and the combination (c). (2) The spacing-loss, the thickness-loss and the gap-loss factors of the combination (a) are the same formulations as those of the traditional longitudinal magnetic recording. However, the above loss factors of the combination (b) and the combination (c) are not independent respectively and each factor depends on the spacing, the thickness of the perpendicular magnetic layer and the gap length or the main pole thickness. (3) In cases of the (b) and (c), the dependence of the readout voltage on the spacing increases as the thickness of the perpendicular magnetic layer decreases. (4) The wavelength of the first null point of the combination (b) is greater than the main pole thickness and that of the combination (c) is greater than the gap length. As the distance between the head and the high permeability layer becomes small, the wavelength of the first null point of combination (b) approaches the main pole thickness, on the other hand, that of combination (c) shifts toward wavelength longer than the gap length.

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Recording and reproducing characteristics of perpendicular magnetic media by single pole heads have been studied and compared with the results of analysis of a surface magnetic potential model. CoCr/FeNi double layer media were prepared by D.C. magnetron sputtering. The dependences of recording density and reproduced voltage of the media on the thickness of the CoCr layer and perpendicular coercive force are discussed. Those dependences are well explained qualitatively by the consideration of inplane magnetization and transition width of the surface magnetic potential of the CoCr layer.

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A differential detection system of magnetic contrast with control grid in the scanning electron microscope is proposed, and its application to the magnetic contrast improvement for perpendicularly recorded magnetization is discussed. The system consists of two symmetrically placed detectors and a differential amplifier. The output voltage of each detector is fed back to a control grid placed between magnetic film and detector.
It is shown that the detected signal amplitude of the system with control grid is 3 times greater than that of the system without control grid for perpendicularly recorded magnetization on Co-Cr film. The differential amplitude of the twin detectors is twice the amplitude of each detector in the system. Perpendicularly recorded magnetization of 3 micron bit length on Co-Cr film is detected with the system. These results suggest that the system may provide a convenient means to observe recorded pattern on magnetic films and show a step towards an electron beam readout in high density recording.

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The reliability of rare earth-transition metal (RE-TM) alloy films with a multilayer structure which attains a high signal to noise ratio (S/N) is discussed. In order to study the reliability of the magneto-optic (M-O) medium, the accelerated aging tests were performed by changing the ambient temperature andtor humidity (80°C, 60°C 95% RH). The effect of environment on magnetic properties evaluated by Kerr hysteresis loop was also examined.
In a high temperature environment, coercive force Hc changed drastically for the M-O media with oxides (SiO₂) employed for the overcoating or intermediate layers. On the other hand, those with the RE-TM layer sandwiched between AIN layers exhibited little change of Hc. Using Auger Electron Spectroscopy (AES), we found that oxygens were incorporated into the RE-TM layer of the former but hardly detected for the latter. It is thought judging from the AES results and the trend in change in hysteresis loop that degradation of Hc in the medium with an oxide layer is caused by selective oxidation of RE atoms.
The multi-layer M-O medium with RE-TM layer sandwiched between nitride layers promises high reliability as well as high S/N ratio.

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The polar Kerr magnetooptical effect has been used as the main method to measure the magnetization characteristics of films with perpendicular magnetic anisotropy. The author found, however, that on some occasions the shape of the polar Kerr loop as well as the Hall loop changed remarkably (or drastically in some cases) with the orientation of the sample in the investigation of rare earth-transition metal alloy amorphous films. This is due to the cooperative effect of the in-plane or oblique component of magnetization in the sample film and the imperfect perpendicularity of the magnetic field in the polar Kerr apparatus. There is a possibility that such an effect leads to serious errors and misunderstanding in the measurement of perpendicular anisotropy films containing in-plane magnetic component, because some degree of deviation of field from the film normal is unavoidable in actual polar Kerr systems. Therefore, it is very important to examine the perpendicularity of the magnetic field of the magnet in the polar Kerr system before the experiment. However, it is difficult to measure the deviation angle of magnetic field by the ordinary techniques. This paper presents an original method to measure the perpendicularity of the magnetic field using an evaporated nickel thin film with oblique uniaxial magnetic anisotropy. In this method, the deviation angle of field can be obtained from the ratio of the maximum coercivity to the minimum one of the Hall or Kerr loop when the Ni film is rotated on the sample stage.

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The magnetic and magneto-optic properties of amorphous Tb.₁₇ (Fe_1-yCo_y).₈₃ and Dy.₂₀ (Fe_1-yCo_y).₈₀ films have been investigated.
As in the case of Gd.₂₆ (Fe_1-yCo_y).₇₄ films, an increase of the Kerr rotation θ_K. with increasing Co content y has been found for Tb-(Fe_1-yCo_y) and Dy-(Fe_1-yCo_y) films in the range of 0<y<0.3, measured at room temperature with a wavelength of 633 nm. The enhancement of θ_K is considered to be mainly due to the rise of the Curie temperature T_C caused by the Co substitution. Another reason might be the increase of the Fe-Co moment at 0 K.
The dependence of θ_K on wavelength λ in the range of 400 nm<λ<800 nm has also been measured for these films. The results show that the slope of the normalized spectrum ((1/θ_K)·(dθ_K/dλ)) decreases with increasing y, approaching the spectrum for pure Co metal. In addition, a dependence of the spectra on the type of rare earth atoms could be seen for short wavelength (λ∼400 nm).
The product of magnetization and coercivity of Tb-(Fe_1-yDo_y) films increases with increasing y at room temperature in the range of 0≤y≤0.3. This may also be attributed to the rise of T_C.

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Rare earth-transition metal amorphous alloy films are promising for use as a magnetooptical memory material. Corrosion resistance as well as magneto-optical properties is very important to obtain highly reliable memory media. Therefore, a study was made on improving both corrosion resistance and magneto-optical properties for TbFe alloy films by adding Ni and/or Co. Corrosion resistance was estimated quantitatively by measuring optical transmittance changes of films immersed in a 1N NaCl solution. Tc increased when Ni was added in TM rich region, and this increase in Tc decreased with increasing Tb concentration. But in Tb rich region Tc was decreased by the addition of Ni, and Tc increased steeply when Co was added. θ_k increased when Co was added and decreased gradually when Ni was added. The additions of these materials caused remarkable increase in corrosion resistance. From the results, it is concluded that memory media having both high corrosion resistance and good magneto-optical properties can be obtained by using TbNiCoFe amorphous films.

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High-density information storage by means of magnetic holography is demonstrated by using amorphous TbFe thin films as a magnetic hologram medium. The object beam, which emerges from a two-dimensional information pattern (in most cases 35 mm photographic films), is focused on TbFe film by a lens using the spatial Fourier-transform pattern. A magnetic hologram, that is, a magnetic domain pattern corresponding to the interference pattern of the object beam and the reference beam, is established on the TbFe film by thermo-magnetic writing. A Q-switched ruby laser (of peak light power=0.6MW and light pulse durations30 ns) was used as the writing light source. An illuminated spot, from 0.2 to 1 mm in diameter, was chosen depending on the size of information. Image reconstruction was done by means of either the Faraday effect (transmitted light) or the polar Kerr effect (reflected light) using a first-order diffracted beam. A He-Ne laser (1 mW or 30 mW) was used for the reconstruction light source. It was confirmed that satisfactory images of not only documents but also picture images can be reconstructed by magnetic holography. The storage density estimated from the preliminary experiment is about 4×10³ characters/mm². Some considerations for improving the reconstructed image quality are also described.

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From the viewpoint of the magneto-optical recording, it is desirable to realize on the recording media both a larger magneto-optical Kerr rotation angle and higher sensitivity for writing. We found that these can be achieved by substituting Co for some of the Fe atoms when preparing amorphous TbDyFe films by an rf sputtering method.
Measurements were performed of the changes in Kerr rotation angles, magnetizations, coercive forces and Curie temperatures caused by doping Co to TbDyFe with low Curie temperatures. The composition of the films was analyzed by EPMA, and on some samples bit patterns were written by means of an Ar-ion laser (5145 Å).
The maximum value in Kerr rotation angle, 0.52°, was obtained in the series of 70 at.% 3d transition metals and we found that (Tb₄₉Dy₅₁)₃₃(Fe₈₉Co₁₁)₆₇ is the most suitable for practical application.

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Amorphous Tb-Fe films were prepared on thin carbon film and glass substrates by RF sputtering method. The films were irradiated with pulsed Ar laser beam, the energy range of which was that commonly adopted for thermo-magnetic recording. Thermal effects were studied mainly by transmission electron microscopy.
The thermally influenced area depended largely on the film thickness over the range from 200 to 2000 Å. he structure of the irradiated areas changed from amorphous to crystalline, while magnetization of the corresponding areas turned from perpendicular to in-plane orientation. In a 500 Å Tb₃₀Fe₇₀ film on a carbon film substrate a circular area of 2.5 μm in diameter was crystallized by one 4 mW pulse of 1 μs. The damage was more evident in thinner films.

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Magnetic properties and the magneto-optical Kerr effect were investigated in the multilayered amorphous GdCo/TbFe and GdTbCoFe/TbFe films prepared by R.F. sputtering. As a result, the following have been clarified: In the case of the multi-layered films in which the magnetic moments of TM atoms between two films arrange oppositely with each other, anomalous magnetic Kerr rotation hysteresis loops are observed but they become normal loops with increasing film thickness of GdCo layer. On the other hand, in the multilayered films with parallel arrangement of TM atom moments, the behavior of hysteresis loops is analogous to the case of single layered film, moreover θ_k increases monotonically with the increasing film thickness of GdCo or GdTbCoFe layer.

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Single crystals of highly Bi-substituted gadolinium iron garnets have been grown by an improved flux method using Bi₂O₃ as a flux. Faraday rotation and optical absorption were measured in the near-infrared region at room temperature. The Faraday rotation of Gd_3-xBi_xFe₅O₁₂ increased linearly with x up to 1.15 and the magneto-optical figure of merit reached 180 deg./dB at 1.0μm in Gd_1.85Bi_1.15Fe₅O₁₂. By using this crystal as a Faraday rotator, a compact optical isolator has been developed for near-infrared light. The optical isolator featured <1 dB insertion loss and 36dB isolation at a wavelength of 1.15μm.

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Guided-wave properties and magneto-optical mode conversion efficiencies were measured for LPE-grown YbPrBiGaIG films with different growth temperatures. Nearly 100% TETM mode conversion was reached by compensation effect of the film birefringence on the phase mismatch between TE and TM waves. The contribution of “growth-induced birefringence” with the magnitude of 3∼4×10^-4 was observed in addition to the stressinduced one. Together with the high magneto-optical coupling constants in LPE-grown Bi substituted iron garnet films, the positive sign of the growth-induced birefringence is highly favorable for nonreciprocal guided-wave devices. The coupling constants are 13.3 rad/cm in the Faraday configuration and 6.5 rad/cm in the Voigt configuration for the phase-matched film.

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Annealing effect on magnetostriction was studied for Fe₄₀Ni₄₀Si₂B₁₆ and Co₄₀Ni₄₀Si₈B₁₂ amorphous alloys. The λ_s in Fe-Ni based alloys is increased by annealing, while λ_s in Co-Ni based alloys is decreased. The relaxation process of λ_s in Fe-Ni based alloys, in which the one-ion term is dominant, can be described with a simple exponential curve having a low activation energy of 0.2eV. From the value of activation energy, it is inferred that the change in λ_s is basically associated with the topological short range order due to the excessive free volume and free from the compositional short range order. The λ_s in Co-Ni based alloys with the dominated two-ion term is responsible for the chemical short range order as the induced anisotropy.

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The interference functions and the distribution functions for amorphous Cr_1-xGe_x alloys with 0.3≤x≤1.00 are determined, and their electrical resistivity and magnetic susceptibility are measured from 4.2 K to 300 K. For x≤0.83, a splitting of the second peak of the interference functions is observed, and electrical resistivity is scarcely dependent on temperature. These results are interpreted as features of amorphous metals or alloys. For 0.67≤x≤0.83, the electrical resistivity shows a maximum at T_max, and T_max increases with decreasing Ge content. This behavior indicates a systematic change of the Fermi wave number with decreasing Ge content. For x=0.5, a minimum of the electrical resistivity is abserved, which may be due to the Kondo spin flip scattering. The magnetic susceptibility for 0.43≤x≤0.72 shows a Curie-Weiss like behavior with small effective Bohr magneton number P_eff. For 0.52≤x≤0.72, P_eff is independent of Ge content. These magnetic properties are explained by assuming the presence of magnetic clusters of Cr atoms.

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This paper describes some surface features of rapidly solidified crystal ribbons and its relation to the pupdle flow behavior with particular attention to the Nozzle-Roll gap. Magnetic properties of the rapidly quenched High Silicon Iron Alloy ribbons are strongly affected by the ribbon surface topography. Therefore, ribbon surface roughness is examined in connection with pit formation as well as fluid-flow behavior. It is shown that pit size strongly depends on the Reynolds number (Re) and that there is a Critical Reynolds number (Re_crit). Below Re≤Re_crit, the puddle flow becomes a laminar flow. The increasing rate of pit size is so small that a smooth ribbon can be obtained. The apparent iron loss (W_0.5/50) halved and the apparent flux density (B₁₀) is doubled resulting in an improvement of the magnetic properties of the ribbon.

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The structure and magnetic properties of Sm(Co, Fe, Ni, Cu)₇ ribbons prepared by a rapid quenching tecnique are investigated with successive annealing at various temperatures. A maximum coercivity of about 6 kOe is obtained for the specimen aged by two steps, namely aged at 800°C for 4 hours and then annealed at 600°C for 3 hours. The cellular precipitate structure composed of 2-17 and 1-5 phases is found in samples with high coercivity. This aging behaviour is very close to that of the sintered alloy with the same composition.

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Magnetic and magneto-optical properties of amorphous Tb-Co and Dy-Co films prepared by R. F. sputtering were investigated. Magnetic properties such as 4πM_s, θ_k, T_c, T_comp and X-ray halo pattern hardly change in the region of positive substrate bias voltage (V_b). On the other hand, they change considerably by increasing negative V_b from 0V to -150V because rare-earth atoms of the films are resputtered preferentially. V_b dependences of perpendicular magnetic anisotropy (K_u) of amorphous Tb-Co and Dy-Co films show minimum values around the V_b’s of -60V and -80V, respectively. These phenomena seem to be explainable in terms of a change of microscopic structure which originates from the preferential resputtering effect.

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Annealing of ion-implanted garnet films in hydrogen atmosphere has been studied. It was found that the anisotropy field change, Δ(H_k-4πM_s), for He⁺ implanted films was enhanced after the annealing. Δ(H_k-4πM_s) for H₂⁺ implanted films annealed in hydrogen atmosphere was kept larger than for samples annealed in air. Since there was little effect on H_k-4πM_s for unimplanted bubble layers after the annealing, this enhancement arises from implanted layers. Lattice strain, Δa/a, was nearly equal to that for samples annealed in air. The enhancement of Δ(H_k-4πM_s) disappeared with annealing in air above 350°C It is well known that H+ implantation shows excess contribution to ΔH_k which is not attributable to simple magnetostriction but rather to the chemical effect. The enhancement Δ(H_k-4πM_s) by hydrogen atmosphere annealing was similar to this “hydrogen chemical effect”. 0.5 μm bubble propagation was studied using He⁺ implanted films (1.8 eV/ų damage level) annealed in hydrogen gas for one hour at 300°C The propagation margins were measured around 2.5 μm pitch “good” loops. The minimum rotating field was 50 Oe and bias margin was 40 Oe at 65 Oe rotating field.

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Transfer modes from cache to storage loops in ion-implanted bubble devices with on-chip cache organization have been studied. The advance mode (MODE-A) in data transfer from cache to storage loops (c-s transfer), which is required by the data recurrence condition, was simulated using the gate pseudo-operation technique where current was not applied to the gate conductor. The difference in bubble behaviors in c-s transfer operation among three samples with different δλ values (≡λ₁₀₀-λ₁₁₁) can be explained qualitatively based on the lattice strain relaxation model. According to the model, a strong negative chargedwall due to the difference between magnetostriction constants, λ₁₀₀ and λ₁₁₁, rises at the pattern edge normal to the [121] direction, which is almost equal to the rotating drive field direction corresponding to the gate pulse end phase for MODE-A operation. A potential barrier formed by the negative charged-wall is found which prevents a bubble from moving in the right direction along the corner pattern edge. Therefore, in order for c-s transfer to operate stably in MODE-A, the difference between λ₁₀₀ and λ₁₁₁ must be sufficientlly diminished.

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An improved method for simulating the motion of vertical Bloch lines in a domain wall of arbitrary shape is presented together with the results on an s=0 bubble containing two Bloch lines. The formulation of a previously developed simulation program has been extended to include in-plane magnetic fields with origins both external and internal to the domain wall, so that the magnetostatic interaction between the Bloch lines may be taken into account. A numerical scheme has been devised which minimizes the total number N of points used to represent the magnetization structure along the wall by allocating them with high density only in the neighborhood of Bloch lines. The CPU time necessary to simulate a 1-μs motion with a time step of 1ns and N of 80 is about 9 minutes on a HITAC M-280H. The program is expected to become a useful tool for developing domain-wall devices utilizing Bloch lines.

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Dual conductor-sheet magnetic bubble devices are attractive as high-performance memory components because of their high-frequency performance and designability. This paper describes a method of improvement for major/minor organization including transfer gate carried out with scaled-up models and computer simulation. Computer simulation for 1 MHz operation was performed with a set of parameters based on the high-mobility film of (YBi)₃(GaFe)₅O₁₂ grown on a (110) garnet substrate. It has been clarified, through our method, that homogenization in the size and the depth of the potential wells is essential for achieving good performance. In order to examine the possibility of low power dissipation, the relation between coercive force H_c and minimum drive-current density J_min has been investigated.

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This paper describes the operating characteristics of the combined sheet bubble circuit. The circuit consists of dual conductor-sheets and a perforated permalloy-keeper formed on the surface of the upper conductor. First, the problems peculiar to the combined sheet circuit, i.e. bubble-permalloy interaction and the interaction between the levels, are discussed. The latter interaction is considered in the form of field distribution along propagation paths, and the former in the form of two hypothetical loci of bubble propagation. The field distribution is measured on scaled-up models and is approximated by the equation h₁·h_x[cos (2π/λ)x+0.5 sin (4π/λ)x]. A distortion factor of a bubble-driving field is calculated by using this equation in order to indicate the interactions quantitatively. Secondly, the results of experiments which confirm the effect of the combined sheet bubble circuit are discussed. The combined sheet bubble circuit without return conductor was fabricated on (YSmLuCa)₅(FeGe(₅O₁₂ material sustaining 5 μm-bubbles. The thickness of the permalloykeeper is 0.03 μm. The bubble circuit was driven by sinusoidal currents at frequencies of 100 kHz. 300 kHz and 500 kHz.

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The authors have devised a current-access optical matrix switch employing a bubble which has two rest positions within a well dugout on a magnetic garnet film. Satisfactory agreement was found between theory and experiment on the rest positions, determined by the demagnetizing field in the well. Various matrix configurations for driving bubbles have been examined by using a scaled-up model. Discussions are given of the characteristics evaluation in order to achieve an optimum access method.

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The magnetic properties in a film with perpendicular anisotropy prepared from two elements evaporated simultaneously from two sources depends on the shape of columnar grain and distribution of these elements in the column. The properties originate in the film preparation conditions: incidence angle and composition ratio. The relation between the columnar grain structure and these conditions for Fe-Cu films evaporated simultaneously, is investigated on the basis of simulation of columnar grains, analysis of magnetic anisotropy and crystallographic study by X-ray diffraction.

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Film fabrication of polycrystalline ferric borate (FeBO₃) by reactive rf-sputtering was attempted using targets composed of thin iron sheet and B₂O₃ tablets. The films prepared by the optimal sputtering conditions are amber in color and have a high transmittance in the visible and the near infrared regions. The wavelength of the absorption edge (λ_c≅450 nm) and the refractive index (n=2.1 at λ=633nm) are in good agreement with those reported for FeBO₃ single crystal, but the absorption constant (α≅1000cm^-1 at λ=633 nm) is about five times larger than that of the single crystal. Unfortunately, the precise identification of the crystallographic structure of the films has not yet been successfully done, but judging from diffraction measurements and FT-IR spectra, our samples are in a comixture state of Fe-B-O system dominated by FeBO₃, whose threefold axis is aligned parallel to the film normal. We found that our samples exhibit strong ferroelectricity at room temperature. The saturation polarization P_s=0.57μC/cm² is more than twice that of rochell salt. Thus our samples are somewhat different in crystallograghic structure from bulk crystals. The co-existence of ferromagnetism and ferroelectricity at higher temperatures offers an interesting material for not only solid state physics studies but also application to opto-electronic devices.

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The oxidation process of Fe₃O₄−γ-Fe₂O₃ intermediary films (3000Å thick) was investigated using TEM and transmisson electron diffraction and the cause of coercivity increase in the films was discussed. The intermediary films were prepared by annealing Fe₃O₄ films in air at 250∼270°C for 10∼45min. In order to observe the textures near the surface and the inner part of the film, the samples for the TEM observation were prepared using an ion milling technique. It was revealed that the grains of the films grow from 300Å to about 1500Å at the beginning of the oxidation, followed by the transition to γ-Fe₂O₃. The difference in the oxidation states between the surface and the inner part of a film was displayed for the oxirlation conditions using the technique.

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Young's modulus of amorphous Fe-B, Fe-P, Co-B and (Fe, Co, Ni)₇₇Si₁₀B₁₃ alloys has been measured using an ultrasonic delay line method in magnetic fields up to 4 kOe in the temperature range from R. T. to 600°C. Young's modulus measured under the saturation of magnetization E_s in these amorphous alloys depends on the molar volume V_mol as E_s∝V_mol^-2.

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Intermetallic compound Hf_1-xTa_xFe₂ with the hexagonal Laves phase structure is an itinerant electron system in which the ferromagnetic and the antiferromagnetic component of spin fluctuation modes coexist. A first order phase transition occurs from ferromagnetic to antiferromagnetic state with increasing temperature in the Ta concentration range 0.1 < x < 0.3. The magneto-optical Kerr rotation of Hf_0.8Ta_0.2Fe₂ has been measured in the wavelength from 300 to 700nm. The temperature dependence of the Kerr rotation shows a discontinuous change at the ferromagnetic to antiferromagnetic transition temperature.

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Partial crystallization is an effective technique to reduce high frequency core loss in iron-based amorphous ribbons. In this paper, we report a new method to control the number of crystalline particles in amorphous matrix and to reduce high frequency core loss.
Fe₈₀B_20-xZr_x ribbons (x=0, 0.2, 0.5, 0.7, 1.0) were prepared by a rapid quenching technique. Although as-prepared Fe₈₀B₂₀ ribbons are completely amorphous, ribbons containing zirconium are locally crystallized during rapid quenching. The micro-crystal precipitates (Fe₃B+Fe₂₃B₆) are dispersed in the thin free surface layer and their number can be controlled by varying zirconium content. The controlled precipitates suppress the eddy current loss and reduces the high frequency core loss. The core loss (B_m=0.3 T, f=60 kHz) in Fe₈₀B_20-xZr_x ribbons shows a minimum at x=0.7 and the minimum value of core loss is about 80% of that in the completely amorphous Fe₈₀B₂₀ ribbons. Stability of magnetic properties in Fe₈₀B_19.3Zr_0.7 ribbon was checked and it was confirmed that the core loss is kept constant up to 600 minutes for 350°C annealing.

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The variation of domain structure with sheet thickness in single crystal plates of 3% Si-Fe having near (110) [001] orientation was studied experimentally and theoreticlly in the thickness range 0.3-0.5 mm. It was found that the abrupt widening of the domain wall spacing and the disappearance of the sub-domain occur below about 0.1 mm. This can be explained by the increase of magnetostostatic interaction between the free poles at the upper and lower surfaces of the plate and subsequent decrease of the inclination angle of the magnetization out of the sheet plane.

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A novel dry type high gradient magnetic separation (HGMS) device comprising a fluidized bed is investigated for the purpose of obtaining pulverized Chinese coal beneficiation. The ash component of Chinese coal, indicating high magnetic susceptibility, can be cleaned well by this device compared with other coals such as Australian coal. The separation performance of the device tested is related to the magnetic field, gas velocity, processing time and process repetition frequency. The fluidization of the coal was found to be the most essential factor for obtaining good separation. Increase in magnetic susceptibility of the coal is observed by means of a pre-heating process, but improvement in the separation performance concerning the ash is not yet confirmed. Correlation points between the ash reduction and the coal recovery are centered in one curve in spite of the various parameters. About 30% ash reduction at 90% coal recovery and 45% ash reduction at 80% coal recovery are expected.

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High Gradient Magnetic Filter (HGMF) applied to the purification of power plant primary water has recently attracted much attention. In the application of HGMF to the water treatment of power plants, especially nuclear power plants, reliabilities of matrix (filtering medium) as well as removal performance for cruds (insoluble corrosion products) are considered to be important factors. To satisfy these factors, a new filtering medium named Diffision Bonded Matrix (DBM) has been developed and the test results are reported. Filtering efficiency and mechanical stiffness of DBM were examined using HGMF pilot test units consisting of 160 mm diameters x 240 mm length filter. The filtering velocity and the magnetic flux density used in this test were 800 m/h 5 kG, respectively. The filtering efficiencies and of 85-100% were obtained for artificial cruds for DBM. The DBM indicated slightly better filtering efficiency than for conventional wool matrix under the same filtering and matrix conditions. The DBM kept its original mechanical properties and very few pieces of fibers were broken off while the conventional wool matrix lost its volume elasticities and the considerable amount of fibers was broken off during the test operation. The results described here demonstrated the applicability of DBM for treatment of BWR primary water by High Gradient Magnetic Filter.

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The so-called forward problems of the electroencephalogram (EEG) and magnetoencephalogram (MEG) are investigated. The electrical conductivity of brain lesions varies with pathological situations such as edema and calcification. An internal electrical source around brain lesions in the head is assumed to be a current dipole, and the spatial patterns of electrical potentials and magnetic fields over the surface of the sphere due to the current dipole are calculated. The effect of the tissue inhomogeneities of brain lesions on spatial patterns of abnormal EEG and MEG is studied by means of a computer simulation. The forward problems of evoked potentials and evoked magnetic fields are then investigated. The propagating electrical source in the afferent nerve fibers is assumed to be a current dipole in a fixed point at an instant period. The spatial distributions of electrical potentials and magnetic fields due to the current dipole are mapped, changing the conductivity of the inhomogeneous areas in the head such as skull, ventricles and brain lesions. The results show that the spatial patterns of EEGs and MEGs are influenced by the inhomogeneities in the head.

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Co-rich amorphous magnetic cores exhibit high gain and low noise in the high frequency range. However, flux resetting characteristics have not been studied in this region. In this paper, we report the Control Magnetization Curves (CMC) of amorphous magnetic cores in a 1 kHz-200 kHz frequency region.
At f=200kHz, amorphous small cores with toroidal shape exhibited high gain and high reset flux density as compared with Mn-Zn ferrite small core.
The characteristics of the amorphous ring cores in the proportional region of the reset characteristics was independent of exciting frequencies from 50 Hz up to 50 kHz. Core noise of the ring cores is much smaller than that of the toroidal cores which have the same composition.

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The operation of valve-type temperature-sensitive magnetic actuators utilizing magnetic compensation alloys are described. The dynamic characteristics of the actuators are analyzed using a finite-element method on the basis of simple assumptions. The calculated values are in good agreement with the experimental ones.
This analytical method is useful for designing an actuator with high performance.

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A Soft Heating method using metal-ring and temperature-sensitive ferrite rod is proposed for increasing the heat generation at room temperature. Typical temperature characteristics of the heat quantity have been obtained experimentally. Furthermore, by introducing an equivalent circuit for the Soft Heating, the following two properties have been clarified: 1) Generating heat at room temperature is determined mainly by the demagnetizing factor of ferrite rod; 2) Residual heat over the Curie temperature can be decreased by increasing the apparent permeability of ferrite rod.

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New rotor-current detection methods for squirrel-cage induction motors are presented using amorphous micro-core magnetometers which detect magnetic fields of 10^-5 −50 Oe and of dc −10 kHz. The magnetometer is composed of two amorphous cores 0.5-mm in diameter and 2-mm in length, and two switching transistors constituting a multivibrator bridge circuit with a dc output. Two methods are used for rotor-current detection: (i) detection of the flux due to the end-ring current by setting the cores into a narrow space near the end-ring, and (ii) detection of the rotor axial ripple flux due to the rotor currents through the skewed rotor bars by setting the cores in the stator slots of 0.6-mm depth.

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New jitterless pulse generator elements are presented using as-prepared amorphous magnetostrictive wires. These wires induce very sharp voltage pulses of ∼6V/cm² · Oe · turn at pick-up coils due to the large Barkhausen effect and of ∼6 V/cm³ · Oe between both ends of the wire due to the Matteucci effect against wire-axial ac fields of more than 0.1 Oe and of 0.01 Hz∼10 kHz. Jitter of pulse inducing phase is less than 1/10 that of Wiegand wires. These stable amorphous wires are suitable for applications to high-resolution rotary encoders for accurate speed sensing or position sensing in the fields of “mechatronics” such as power motors, industrial robots, automobiles, and industrial measurement instruments. Effects of etching and heat treatments on pulse induction and higher-harmonics generation are also investigated.

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