Amorphous Co-Ti films of about 1 μm in thickness have been prepared by r.f. co-sputtering technique. The coercivity of Co-Ti films is found to depend strongly on the sputtering conditions such as the substrate bias and the argon pressure. Soft magnetic films with the coercivity less than 50 mOe are obtained at the substrate bias V_b of −30∼ −50 V. Through the negative bias, the oxygen content in films decreases from 4at.% (V_b = 0V) to less than 1 at.% (V_b = −30∼ −50 V) and further the columner structure observed in the films at V_b = 0V disappears in those at V_b = −30V.
When the films are annealed in a magnetic field, the coercivity is almost constant up to 400°C, while the uniaxial magnetic anisotropy is induced above 200°C.

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Influences of oxygen on magnetic properties in amorphous GdCo sputtered films were studied by annealing them in air at various temperatures. Oxidation causes the increase in the perpendicular magnetic anisotropy energy K_u for zero bias sputtered films whose film structure is columnar, while it causes the decrease in K_u for bias-sputtered films whose film structure is ultra-fine or fiber-like. It is found from AES depth profiles that there are two modes in the oxidation process, and that they depend on the film structure. Mode I and II are observed in the columnar and the fiber structures, respectively. The surface oxidized layer in the low-bias films with the columnar structure, where the magnetization lies in the film plane, is fairly stable against annealing, and a small amount of oxygen penetrates uniformly into the internal part of the film up to the substrate (mode I) along the columnar boundaries. In the mode I oxidation, K_u of the order of 10⁴ erg/cm³ is induced by the preferential oxidation of the boundaries. On the other hand, the surface oxidized layer with the fiber structure propagates toward the substrate (mode II). This is more prominent for higher bias films. The mode II oxidation causes the decrease in K_u.

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Static magnetic properties such as coercive force, hysteresis loss and magnetic flux density have been studied under various tensile stresses up to about 140 MPa for an amorphous Fe_79.3Si_9.2B_11.1Al_0.4 alloy.The tensile stress dependence of coercive force has been discussed by a simple model based on the domain wall motion proposed by Kondorski and Kersten. The dependence can be explained by assuming two compressive stresses σ_c1 and σ_c2 which exist in the bulk portion and surface layers, respectively. The values of σ_c1 and σ_c2 are estimated to be 1 MPa and 7 MPa, respectively.

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Amorphous ribbons have a large core loss at high-frequency driving field because of their wide magnetic domains. In this paper, we report on the improvement for high frequency loss by scratching or local crystallization.
The core loss measured at 20 kHz decreases by scratching or local crystallization, and this effect becomes remarkable with decreasing the space of scratches or locally crystallized regions. On the contrary, the squareness ratio of the DC hysteresis loops becomes small and then the DC hysteresis loss increases after scratching or local crystallization.
It is observed that magnetic domains are refined by scratching. However, this refinement occurs only in the vicinity of scratches when the space of scratches is wide. When the spaces are narrow, domains are refined in all the region between scratches and the number of domain walls is lagre. In the case of local crystallization, it is also observed that domains are refined.
These results suggest that the observed improvement in high frequency core loss can be attributed to the decrease in the eddy current loss which is caused by the refinement of magnetic domains.

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We have investigated the delay time properties of magnetoelastic wave (ME wave) in amorphous Fe-B films prepared by rf-cosputtering. Films were deposited as thick as 10 μm onto aluminium foils of about 20 μm in thickness, which enable us to observe the bulk mode of ME wave. We also made similar experiment for liquid quenched Fe₈₀B₂₀ ribbons for comparison. The fractional change of the sound velocity |C−C_s|/C_s by the application of a static bias field H_b is about 4% for the film (atf = 100 kHz), which is about one third smaller than that of the ribbons. This is considered that the films used here are still magnetically hard (H_c = 1 Oe for the films, while 0.1 Oe for the ribbons) mainly due to strong constraint from aluminium substrate.
Analysis was made on the delay time properties of ME wave in terms of one-dimensional elastic bar taking the micro-eddy current damping into consideration, by which the bias field and the frequency deoendences of the sound velocity can fairly well be explained.

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Ribbon formed Fe₂P_1-x(Mn, B, Si, Ti)_x, (Fe_1-xCo_x)₈₃B₁₇ and (Fe_1-xCo_x)₈₃p₁₇ have been prepared using a rapid quenching technique and their magnet properties have been examined after annealing in the temperature range from 300 to 80°C. In these alloys, Fe₂P_0.4Mn_0.6 alloy exhibits the best magnet properties, H_c∼350 Oe, B_r∼7000 G and (BH)_max∼1.4 MG · Oe. These magnet properties originate from a metastable phase precipitated in the annealing process.

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A detailed examination has been carried out on magnetization distribution of bubble and stripe domains in Ho_xCo_100-x (14 ≤ x ≤ 30) by high voltage electron microscopy in the defocused mode. Spot-like images were observed in bubble and stripe domains, even in a very small bubble of about 1500 Å in diameter. Based on the results of the change in images as a function of defocus distance and applied field, the spot region is proposed to correspond to a so-called “core”, around which the magnetization distributes in a similar way to a vortex.
A calculation has been made to obtain a size of a core on the basis of a model proposed for the magnetization distribution of a bubble. It is found that the diameter of a core is about 200 to 300 Å, provided that the exchange constant A = 1 × 10^-6 erg/cm for Ho-Co alloy films. This result is favorably compared with the observed value.

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Magnetoresistive characteristics of Fe-Ni alloy films (MR films) prepared on glass substrates, Ti films or insulation films, were examined under various preparation conditions to induce uniaxial magnetic anisotropy in a desired direction of the films, taking into consideration of magnetostatic and magnetoelastic energies.
MR films prepared under the following conditions show uniaxial magnetic anisotropy without dispersion. The conditions are as follows:
1) Thickness of MR films: < 2000 Å,
2) Surface roughness of substrates: < 50 Å,
3) Composition of evaporation source: 83Ni-17Fe (at.%), and
4) Surface condition of Ti films: O₂ plasma oxidation prevents Ti from diffusion into Fe-Ni alloy films.

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The structural and magnetic properties of Bi-doped GdFe films prepared by ionized cluster beam (ICB) technique have been studied by means of X-ray scattering and ferromagnetic resonance (FMR). Preparation of amorphous Bi-doped GdFe films was made by the deposition of Gd and Fe clusters and simultaneous evaporation of Bi onto a glass substrate. In this study, only Fe clusters were ionized. Caluculated reduced density function G(γ) of films shows that the nearest-neighbour bonding peaks are broad as compared with pure GdFe films. The observed peaks in the G(γ) shift clearly toward longer distance by annealing, suggesting the increase of Gd-Bi pairs and the decrease of Fe-Bi pairs. The internal effective field (H_eff = 2K_u/M_s−4πM_s) of as grown Bi-doped GdFe films is larger than that of pure GdFe films, and is able to be positive by annealing. It is concluded that the production of atomic pairs, whose interatomic distance is larger than the Gd-Fe interatomic distance (3.2 Å), are responsible for the increase of H_eff.

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This paper proposes a new method to determine the direction of easy axis in a uniaxial magnetic anisotropy film using the extraordinary (or spontaneous) Hall effect. In this method, the magnetic easy axis is derived mathematically from two magnetic hard directions. The hard directions are obtained experimentally as the magnetic field directions where the Hall characteristic curve loses hysteresis. In order to examine the validity of the method, nickel thin films with oblique magnetic anisotropy were prepared by oblique incidence evaporation, and the Hall effect was investigated on these films, stressing on the field direction dependence of the Hall curve. The experimental results agreed well with the theoretical considerations. It was also found that the hysteresis disappearance was very sensitive to the direction of the applied field H particularly in magnetically well-oriented films. This fact suggests that the Hall method enables high accuracy measurement of the easy axis. Accuracy better than 0.1° may be expected by this method.

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Magnetic garnet films of (YBi)₃(FeGa)₅O₁₂ and (YSm)₃(FeGa)₅O₁₂ systems were prepared for magnetic transcription use. Films with the specific Faraday rotation up to 10⁴ deg/cm, the squareness up to 1 and the saturation field down to 2 Oe can be produced by varying the thickness from 0.5 μm to 9 μm and the saturation magnetization from 6 G to 220 G. Amorphous Dy-Fe films were deposited directly on the garnet films to make composite films. Thermomagnetically induced domains in the former were examined as the transcripted domains in the latter, where the magneto-optical contrast was much improved due to the one order higher Faraday rotation of the latter than the Kerr rotation of the former. High quality of transcription without bias field can be attained only by the garnet films of large squareness. These results show that the composite films is a good candidate medium for thermomagnetic memory systems.

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Strain and anisotropy field profiles in triply implanted layers have been determined by means of X-ray double crystal diffraction and ferromagnetic resonance measurements. Strain profiles are determined by kinematical theory of X-ray diffraction. So far kinematical theory has been widely used for investigating strain profile with less consideration of its applicability to implanted layer. Kinematical expression has been rigorously verified using the Riemann's method, based on Takagi's equation of X-ray dynamical theory. Anisotropy field profiles are determined by solving spinwave equation. Inside the double implanted layers with neon ions, anisotropy field change is proportional to strain. Hydrogen ion addingly implanted, there appears the region with large anisotropy field change near the projection range of hydrogen.

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Growth rate and saturation temperature for the LPE growth of (GdSmTmCa)₃(FeGe)₅O₁₂ garnet films were investigated as a function of R₄ parameter, which is the molar ratio of garnet-forming oxides to total oxides in the melt. Below 800°C, very slow growth rate as low as 0.2 μm/min is obtained by using a melt whose R₄ parameter is 0.10. As the growth temperature decreases, film lattice parameter becomes larger because of the increase in Pb substitution. The Pb content increased up to 0.1 mole/garnet formula unit. Growth induced anisotropy constant K_u^g is smaller at lower growth temperatures. Using low-temperature-growth LPE films, whose characteristics were adjusted for use in the drive layer for 4 μm contiguous disk (CD) device, good CD propagation margin was obtained.

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A simple estimation method for ion-implanted depth in bubble garnet films has been developed exploiting bubble stability model. The model consists of radial magnetization method and image method, where magnetization in the implanted layer is assumed to lie in the film plane due to magnetostriction effect. Bubble stability condition is modified by the radially magnetized layer within the flux matching condition. Bubble collapse field and stripe out field for an implanted film has been calculated as a function of ion-implanted depth by the proposed model. Ion-implanted depth has been inversely estimated by measuring bubble collapse field in 1 μm bubble (YSmLuBiCa)₃(FeGe)₅O₁₂ garnet films. The ion-implanted depth, determined from the stability model has been compared with the depth determined by the Monte Carlo simulation method and the differential etching techniques. The estimated values are well correlated with each other.

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This paper proposes two types of dual-conductor bubble circuits: single- and double-combinedsheet bubble circuits. A combined sheet consists of a perforated conductor sheet and a perforated permalloy keeper which have the same aperture patterns. The permalloy keeper is disposed on the upper surface of the conductor. The single-combined-sheet circuit consists of the perforated conductor sheet in level 1 and the combined sheet in level 2. The double-combined-sheet circuit consists of the combined sheets in both levels. The effect of the perforated permalloy keeper and magnetic interactions between the levels, such as a field distortion induced by the keeper in the adjacent level and magnetic shielding of the first-level keeper, are discussed by use of the results measured on scale-up models. The combined sheet produces a stronger drive field because the permalloy keeper enhances a field produced by the conductor. Therefore, the linear current density required for bubble propagation is reduced, which results in a lower power dissipation. The degree of the enhancement increases with the permalloy thickness. The thicker permalloy keeper produces the stronger magnetic interactions between the levels.

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The ac current distribution in a long thin conductor sheet has been investigated as a first step to understand the frequency dependence of the scaled model for magnetic bubble domain conductor-sheet devices. The current distribution in a conductor sheet without apertures has been estimated experimentally by using a search coil which picks up the planar component of the magnetic field just above the sheet surface. A simple iteration approach has been proposed to calculate the current density by successive approximation method, and the computational results in good agreement with the experiment have been obtained. The current density at the edge portions of the conductor sheet has been shown to increase considerably at a frequency as low as a few kHz depending on the sheet width ω and sheet thickness t. A formula has been derived indicating an upperbound frequency f_c above which the so-called eddy-current effect cannot be neglected: f_c[MHz] = 1.15p [μΩ · cm]/(ω [cm] t [μm]). The principle of the calculation and the salient computational results are given.

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Fabrication process for bubble memory devices with submicron minimum features has been developed. Deep UV contact printing and dry etching technologies are used. A newly developed photoresist, MRS, is used as the deep UV photoresist. The resolution of MRS resist exposed with deep UV light is superior to that of AZ1350J resist with UV light. Permalloy chevron patterns with 0.75 μm gaps were ion-etched through the MRS resist mask. Contiguous disk patterns of 2 μm period with 0.5 μm minimum feature were achieved by plasma etching of Mo/Si film through the MRS resist patterns.

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A high efficiency main-pole-driven perpendicular magnetic recording head (MPD head) has been developed. The MPD head is one-sided with respect to a recording medium, and its driving coil is wound around a thin film main pole attached to a flux enhancing ferrite side core. The recording efficiency of the MPD head was improved by reducing the head dimensions such as the main pole jutting length from the side core end and the side core thickness, and also by employing a double layer recording medium. The achieved recording efficiency of the MPD head was higher than that of an auxiliary-pole-driven head with the almost same dimensions, and comparable to that of a conventional ring shaped head.

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To investigate the reproduction performance of a single pole head in a perpendicular magnetic recording system, the reproduced voltage and the noise spectra have been measured and compared with the performance of a ring head. The ring head in our measurements is the same form as a video head and has the same inductance as a single pole head. Higher reproduced voltage for a single pole head was obtained by using the main pole which was made by a Co-Zr rf-sputtered film having higher saturation magnetization and initial permeability. The reproduced voltage per unit inductance of the single pole head was higher than the value of the ring head, and smaller values of medium noise and rubbing noise were measured in the perpendicular recording. As the result, in our perpendicular recording system, we get the C/N ratio of about 50 dB at the density of 110 kMRPI.

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The application of magnetic films prepared by the oblique incident evaporation, High Incident Nucleation (HIN) method, for micro cassette music tapes has been examined. The following results have been obtained.
1) The coercive force and the gradient of hysteresis curve, (dΦ/dH)_Hc,of single layer films take the maximum values at 1000−1500 Å in thickness, and decrease as the film thickness increases.
2) The multilayer films composed of Al layers and Co-30 at%Ni layers being deposited alternately show the superior magnetic properties even with thicker films.
3) As-deposited films show the large fluctuation of the reproduced output level. By polishing the film surface, it is improved and higher values of the reproduced output are obtained. These improve-ments are due to decreasing of the spacing-loss between recording head and the magnetic film surface.
4) Samples prepared by the improved processes mentioned above, have the coercive force of more than 600 Oe and exhibit the recording frequency characteristics equal or more superior to those of “metal tape”.

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The magnetic contrast (Type I) in a differential detection system in the scanning electron microscope is measured and evaluated. The differential detection system consists of symmetrically placed two detectors and a differential amplifier. The output of a detector in the differential detection system is greater (2.6 times with YFeO₃ platelets and 2.3 times with FeCo anodic oxide films in measurement) than that in a single-ended system, due to a balanced electric field between the two detectors and a specimen. The differential amplitude of the two detectors doubles the output of the one detector in the differential detection system.

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Thermomagnetic writing and erasing properties have been studied for exchange-coupled doublelayered films, which consist of Gd-Fe layer for reading out and of Tb-Fe layer for holding written bits. The minimum bias field necessary for writing or erasing has been measured for various film compositions. The minimum bias field for writing is remarkably large near the compensation composition of Gd-Fe layer. This result suggests that bils are written firstly on the Gd-Fe layer if the Tb-Fe layer is heated above the Curie point and then the bits are transferred to the Tb-Fe layer as it is cooled down through the Curie point. A simple model based on this writing process well accounts for the magnitude of the minimum bias field. The bias field necessary for erasing is generally smaller than that for Tb-Fe single layer films.

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A laser induced magnetization of ErCrO₃ in antiferrornagnetic and weak-ferromagnetic states is observed at temperatures below 77 K by selectively exciting the Cr³⁺ ions with a Q-switched ruby laser light. Dependences of such a magnetization in the c crystallographic direction on the magnetic field and the temperature were measured with a pick-up coil. Two mechanisms contribute to the induction of the magnetization by the laser irradiation. One is a thermal effect and the other an effect due to to the change of spin states accompanied by the optical transitions.

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Impurity effects on the optical properties of bithmus-substituted iron garnet films grown by liquid phase epitaxy have been investigated. Growth temperature dependences of optical absorption coefficient at 0.56 μm and Faraday rotation coefficient at 1.15 μm are presented for (YbPrBi) ₃Fe₅O₁₂ and (TmNdBi)₃(FeGa)₅O₁₂ single crystal films with in-plane magnetization. With decreasing the growth temperature, the absorption and Faraday rotation coefficients increase with the incorporation of Bi and Pb ions. In the Raman scattering spectra, intensity enhancement of the impurity-induced phonon lines is found at 450 and 700 cm^-1. To examine the guided-wave optical properties, a “m-line” spectrometer equipped with a CCD image sensor has been used. Guided-wave properties such as refractive index, absorption coefficient, and TE-TM mode conversion efficiency at 1.15 μm are discussed for (YbPrBi)₃Fe₅O₁₂ films.

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In order to utilize the ferrite which is by-product from the magnetic separation of waste water, a possible use as some magnetic guide or marker has been proposed.
In the present work, three different proto-types of magnetic detector were made. A test road (150 m) which has magnetic markers under the pavement was constructed. It was found that signals from the magnetic marker can be detected from the running vehicle. A miniature model car which was loaded a micro-computer was made. It was assured that the car moved along the magnetic guide ways choosing the proper path which was previously loaded in the computer. To guide blind people, a small magnetic detector was also made.
Throughout the present work, possibility of a practical use as the magnetic guide system has been proved.

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An FM module using ferrite orthogonal cores which have the functions of a sensor and a telementer with an extremely simplified construction is suitable as instrumental and controlling devices. In this paper, an FM tachotelemeter and a variable frequency thyristor inverter are presented as new applications of FM modules.
The FM tachotelemeter which is combined with the FM telemeter and the permanent magnets can simultaneously measure rotating speed and bend of shaft without contact, modulate and amplify the frequency at the same time, and measured from the stop to the high speed rotation continuously. Furthermore, it has good isolation and noise absorption characteristics. This device can be used as a high-reliable multifunctional tachotelemeter.
A variable frequency thyristor inverter can vary the output voltage widely and continuously, and has high-speed breaking and good constant voltage characteristics. It can be used as a power source of high-speed variable motor.

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A new method which is called the “finite element method with size modification” has been developed. This method has the following advantages:
(a) When the flux densities at some points are specified, the sizes of magnets which produce such flux densities can be directly calculated.
(b) As this method needs no repetition, computing time can be considerably reduced.
This new method has been applied to the design of the magnet roll for a cooying machine and an erasing head, etc., and its usefulness is clarified.
The method enables us to design the most suitable magnetic circuit which is composed of many magnets.

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The performance of a parallel stream type HGMS filter using amorphous ribbons is analyzed in consideration of a neighboring wire effect on a particle capture process and an elliptic cross section of the ribbons which has a large aspect ratio, etc. The main theoretical results are: 1) the neighboring wire effect cannot be neglected in a high effective length of the filter, and 2) the effect increases the particle recovery against our conventional understanding. This reason is that the shape effect of the particle capture area dominates the magnetic force decreasing effect.
Some measurements on the removal of fine magnetic particles in two types of colloid are carried out by using an amorphous ribbon filter. The experimental particle recovery agrees well with the theoretical one which is calculated by taking account of a grain size distribution in the colloid and an edge effect of the filter.

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A novel high gradient magnetic separation (HGMS) process for particulate matter cornprizing a fluidized bed is proposed, and some of its test results are reported. A recovery of magnetic particles from glass particles is tested, and its separation efficiency is about 80%. Magnetic beneficiation of coal powder is also investigated. The residual-ash content of the removed matter is about 40%, which is very large compared with the original coal. An improvement of the residual-ash content by the electrostatic effect is also observed.

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