In order to obtain high-density and wide-band recording characteristics, we have tried fabricating longitudinally oriented at inside layer and perpendicularly oriented at surface layer (LIPS) doubleorientation magnetic tapes uslng acicular particles by a single coating process, but a LIPS doubleorientation structure was not achieved. The purpose of this paper is to describe recording characteristics of LIPS tapes with an improved double-orientation structure by over-coating a perpendicularly oriented upper layer on a longitudinally oriented under layer. The prepared LIPS double-layered tape (upper layer of 2.1μm thickness consisting of metal particles with H_c=1.5kOe, under layer of 2.3 μm thickness consisting of magnetite particles with H_c=700 Oe) shows the highest output and widest band characteristics among the prepared perpendicularly oriented monolayer tapes and longitudinally double layered tapes, due to its smooth and perpendicularly well-oriented upper layer and the longitudinal orientation in the under layer.

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For high-density, Wide-bandwidth, and highoutput characteristics, a magnetic tape should have a high Bs, a perpendicular orientation, a smooth surface, a good head contact, and a small longitudinal component. By using alongitudinally oriented at inside layer and perpendicularly oriented at surface layer (LIPS) orienting process, we have made obliquely oriented magnetic tapes with metal acicular particles, of which a tape oriented at 45 degrees had the widest-bandwidth characteristics. But large output improvement was not obtained because of the existence of disoriented particles in the surface layer as a result of a calender treatment. We tried to remove the surface layers with polishing sheets. An obliquely oriented tape (45 degrees) improved shortwavelength outputs (10 dB higher at 0.3 μm) after the thickness of the disorientedlayers was reduced by 0.12 μm

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Rotational hysteresis loss analysis is carried out for MP tapes in order to evaluate the magnitude of the magnetic anisotropy of metal particles and to clarify the effect of the degree of preferred particle orientation on their magnetic properties. Taking account of magnetostatic interactions among particles, it is shown that the mean value of the magnetic anisotropy of metal particles is 7.7 kOe. Furthermore, it is considered that the mean value of the saturation magnetization inside the particles is about 1270 emu/cc. The ratio of H_k(2θ) to H_k^ptc is the key to evaluating the degree of the preferred particle orientation. Here, H_k(2θ) is defined as the macroscopic anisotropy field, which is equivalent to the macroscoplc uniaxial magnetic anisotropy in the tape plane. Correlations between H_k(2θ)/H_k^ptc and the squareness of magnetization curve, coercive force, and remanent coercive force are established.

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Rotational hysteresis loss was analyzed for CoCrTa/Cr thin film media fabricated on glass substrate, to evaluate the infiuence of the microstructure on the media’s magnetic properties. H_k^grain, defined as the magnetic field in which rotational hysteresis loss vanishes, remained at an almost constant value of about 4.0 kOe, independently of the values of the coercive force. It is considered that H_k^grain almost corresponds to the magnitude of the uniaxial magnetic anisotropy field of the grains,and that the coercive force is mainly determined by the degree of intergranular magnetic coupling interaction. In all the films examined, H_c was mainly determined by the switching of magnetization, independently of the degree of intergranular coupling. The calculated results suggest the possibility that, in CoCrTa films consisting of large grains, the magnetization in each grain changes direction as a result of incoherent switching of magnetization.

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The oblique magnetic anisotropy of metalevaporated tapes for audio recording has been studied, using ferromagnetic resonance techniques at 34 GHz. The static field was rotated in the tape plane and the vertical plane. The resonance equation in the tape plane has been derived without approximation. By fitting of the data of the resonance field (H_r) to the equationin the tape plane, the following values of the saturation magnetization (4πM), the intrinsic anisotropy field (H_k), and the oblique angle of the anisotropy axis from the film normal (α) were determined: 4πM=9.63kG, H_k=1.06kOe, and α=60.0°. The resonance fields in the vertical plane are also well fitted, except for a few high-field data. The effect of surface roughness on H_r is discussed.

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The behavior of magnetization vectors in films that are obliquly anisotropic with respect to the film normal, such as ME, MP, and NT tapes, is analyzed by using avibrating sample magnetometer (VSM) that can detect three-dimensional components of magnetization. The films are asymmetric about the easy or hard direction, and this asymmetry is caused by a shift of the easy direction with a decrease in the macroscopic magnetization. The M-H loops of various applied field directions are qualitatively explained on the basis of the symmetry.

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2000-Å thick Co₇₉Cr₂₁ films for hard disk media were deposited on glass substrates by using a facing targets sputtering (FTS) apparatus. RF power supply was used to apply a bias voltage to the substrate, where well-controlled ion bombardment could be applied. The change in the preferential orientation of Co-Cr crystallites, which was caused by biasing a growing film, was investigated. The bias effect caused a change in the preferential growth plane of hcp crystallite from (001) to (100). The easy magnetization direction changed from normal to in-plane, while the squareness (M_r/M_s)_// varied from 0.18 to 0.75. The in-plane coercivity H_c// had an almost constant value of about 250Oe, which was independent of the bias voltage.

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The mechanical and magnetic properties of thinfilm media using newly developed carbon substrates, which have advantages such as light weight, high heat resistance,and non-magnetism, were investigated in comparison with the properties of thinfilm media using conventional NiP/Al substrates. The adhesive strength of a thin-film medium sputtered on a carbon substrate is higher than that of one sputtered on a NiP/Al substrate, because of the formation of Cr-C compounds at the interface between the carbon substrate and the Cr underlayer. The coercivity of a thin-film medium sputtered on a carbon substrate is also higher than that of one sputtered on a NiP/Al substrate, because of the unique surface morphology. High coercivity can be obtained by using a circumferentially textured substrate and a bias sputtering method.

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The segregated microstructures of electrolessdeposited CoNiP perpendicular magnetic recording media with various H_{c (⊥)} of 500, 1000 and 1500 Oe were investigated by using the selective chemical etching technique; Co-rich ferromagnetic regions were preferentially dissolved with an etchant of sodium hydroxide-m-nitrobenzenesulfonic acidethylenediamine aqueous solution. TEM observation of the etched 1500 Oe film revealed an “asteroid“ pattern with hexa-symmetry, which was expected to be a substructure with a Ni-rich composition. It is considred that the Co-rich regions are segregated between the “arms” of the asteroid substructure. The shape of the substructure varied with the H_{c (⊥)} of the films:; no substructure was observed in the 500 Oe film, while a substructure with a needlelike shape and also a quasi-asteroid one were observed in different regions of the 1000 Oe film. The differences in the segregation conditions are strongly dependent on the H_{c (⊥)} of the films. Further investigation of the 1500 Oe film in the thicknees direction clearly indicated that the segregation occurs even in the initial deposition region (30 nm) and that the size of the substructure becomes larger with an increase in the film thickness.

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Co-Cr perpendicular media on rigid substrates were studied. We used a non-texturing glass substrate for perpendicular magnetic hard disks, but the reproduced output at short wavelengths was influenced by the surface roughness of the magnetic recording media. We therefore fabricated Co-Cr perpendicular hard-disk media deposited on different substrates, namely, non-texuring glass, silicon monocrystal, chemically textured alumite, and Mn-Zn ferrite. We compared those substrates from the viewpoints of crystallographic properties, head-tomedium spacing, and recording and reproducing characteristics.

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The dependence of soft magnetic properties on the annealing conditions for Co-based amorphous films with different thicknesses was investigated in detail, in order to obtain films having isotropically high initial permeability at high frequencies. It was found that the microscopic anisotropy of films annealed in a rotating field was increased isotropically by nonfield annealing below the Curie temperature (T_c). Thinner films having isotroplcally larger microscopic anisotropy showed isotroplcally higher initial permeability at high frequencies. This occured because the natural resonance frequency is increased by an increase in the microscopic anisotropy, and the influence of the eddy current on the initial permeability becomes a dominant factor at high frequencies.

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A magnetic domain was observed by using an image lock-in technique for backscattered electron contrast (Type II) with a JEOL 2000FX-II 200 kV electron microscope. A thin-film head without a protective layer was excited by applying a 10 mA_p-p, 100 kHz drive current. Backscattered electron were synchronously detected by using a diode detector and a look-in amplifier, and images were acquired digitally by using a LINK eXL-II system. Backscattered electrons indicated a difference in the magnetic domain configurations in the upper and lower parts of the upper pole, changing the acceleration voltage. Since the location of a pair of black and white lines in a synchronous mode shows the maximum limit of domain wall movement in one drive current period, the observed difference must have been caused by the difference in domain wall movement, that is, the difference in magnetic flux flow. Conversion of the domain configuration from the upper part to the lower part was also observed. Such conversion is possibly one of the causes of noiseafter-write.

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The magnetic field distributions of a single pole head with a doube-layered medium were analyzed by a two-dimensional finite element method. In the recording process, magnetic saturation occurs in the middle of the main pile, and this saturation decreases the head field strength and the sharpness. On the other hand, a large amount of magnetic flux leaks out from the middle of the main pole in reproduction. In accordance with these results, we designed a new main pole structure. As a result, the reproduction and recording sensitivities and the overwrite were improved. Thus, a D₅₀ of 170kFRPI was obtained by combining this new SPT head having an 0.15 μm thick main pole with a double-layered hard disk having an 0.05μm thick Co-Cr recording layer.

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In order to achieve high linear density recording, it is necessary to use an SPT (Single Pole Type) head with a thinner main-pole film. We confirmed that high resolution in reproduction is obtained by a head with a main pole 0.1μm in thickness, but found that the reproduced properties become worse when the head is less than 0.1 μm in thickness. We also found that these properties are closely related to the crosstie domain wall structure.

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A mechanism was investigated for enhancing the reproduced voltage of the ring-type-head/electroless-deposited perpendicular double-layered medium system. The enhancement mechanism was considered to combine the fo1lowing two effects: the “phase synchronization (PS) effect”, due to a semihard magnetic underlayer, and the “double-layered (DL) effect”, due to a softmagnetic underlayer. By proper AC erasing of the reproduced signal due to the underlayer (underlayer coercivity (H_c(u)=50Oe) on a CoNiReP/CoB double-layered medium, the PS effect was confirmed to appear until the recording density of the region was less than 90 kFRPI. The enhancement of the reproduced voltage in a region where the density was higher than 90 kFRPI was still observed after such a proper AC erasing process, and it originated solely from the DL effect.

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The dependencies of reproduced outputs on headto-medium spacings in perpendicular magnetic recording have been analyzed by computer simulation and compared with the equivalent dependencies in longitudinal magnetic recording. In the recording process, the spacing loss coefficient has little dependence on the bit lengths, because the recording field gradient of an SPT head is not significantly changed by a change in spacing. On the other hand, the spacing loss coefficients in the reproduction process change and become larger as the bit length becomes longer. This is because the reproduce sensitivity function of an SPT head is changed by the strength of head-medium magnetic coupling, which depends on the head-medium spacing.

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In the fabrication of Co-Cr films with a continuous vacuum-deposition system, the incident angle of the vapor beam on the substrates affects the recording characteristics of the films with respect to the specing loss. The spacing loss factor rises with an inctease in the anisotropy field H_keff of the film when signals are recorded and reproduced with a ring-type head. For Co-Cr films deposited with the incident angle varying from 20° to -20°, the spacing loss is large, with a factor of 140, while for the films deposited with the incident angle varying from 55° to 20° and from 70° to 20°, the factors are estimated to be 110 and 85, respectively. The former is approximately the same as the value reported in longitudinal recording. The head-to-medium spacing of 40 nm is occupied by a protective layer and a protrusion, which are indispensable for ensuring the durability and playability of the tapes in VCR use. Consequently, films deposited with incident angles varying from 55° to 20° are advantageous high-density recording.

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A new medium magnetization model that takes account of the magnetic interaction of particles has been developed. It is based on the curling magnetization reversal model, and incorporates Atherton’s function for the mean field interaction. It is very easy to build the mean field function into the algorithm of our medium model. It was shown that the new medium model is very effective for fitting not only the MH loops but also the remanence characteristics of longitudinally oriented Ba-ferrite tape. It is expected that more precise simulation analyses will become possible through the use of this medium model.

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A New bit cofinement method using film thickness modulation (FTM) has been studied on the Bloch-line (BL) memory to make the BL pair propagation cmmon to both sides of the stripe domain wall. Since it is necessary to make the modulation pattern edge smooth for low drive-field propagation, we used tapered resist patterns for the ion milling mask and carried out the milling to fabricate 100 nm thickness modulation in an O₂ atmosphere (10^-6 Torr). BL pair propagation was tested with applying the trianglar bias pulsed field with 100 ns rise time and 1000 ns fall time. It was found that the drive field margins did not depend on the propagation direction, because the bit confinement force acts symmetrically on both sides of the domain wall. Furthermore, it was confirmed that the temperature dependece of the drive field margin was larger than that in the conventonal magnetic pattern method.

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Cd_1-xMn_xTe/MnTe multiple quantum well structures were successfully grown on a sapphire (0001) substrate by using the ionized-cluster beam technique, and their optical and magneto-optical properties were investigated. Transitions to the subband levels formed in wells were observed in the optical absorption and magneto-circular dichroism (MCD) spectra. The transition energies shifted widely toward higher energies as the well width decreased. The experimental results for subband energies agreed well with the results calculated by using the Kronig-Penney band model. The change in the MCD peak height with the well width can be explained by the Zeeman splitting of the subband levels and by the oscillator strength of transitions to the subband levels.

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Since in-plane garnet films have no components of magnetization with respect to vertically incident lights, no magneto-optical effects on the light are observed. We supposed that when a Bi-YIG film was positioned obliquely to the incident light, the plane of polarization was rotated owing to the magnetooptical effect, because some component of magnetization with respect to the light path appeared. An in-plane Bi-YIG film was prepared on a Corning # 0317 glass substrate by rf sputtering, and was then magnetized in a magnetic field of 2 KOe. The apparatus for detecting Faraday rotation consisted of a polarization microscope and alight source. On the stage of the polarization microscope, the plane of the Bi-YIG film was tilted at 45°to the stage plane. The apparatus was used to obtain contrast images caused by the remanent magnetization of the in-plane Bi-YIG film. This result indicates that in-plane magneto-optical films can be applied to display devices.

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The track pitch of magneto-optical disks with metal guiding layers was reduced to less than the laser spot size by suppressing crosstalk. The recorded domain width was effectively confined by the width of the recording region in which the guiding layer was spirally removed. Improvement of the CNR was achieved by using the structure of substrate/enhancing layer/guiding layer/interference layer/recording layer. The total thickness of the enhancing and interference layers was adjusted in order to increase the Kerr effect enhancement, and a CNR of 47.1dB at 3.73 MHz was obtained for a track pitch of 1.0μm. Low crosstalk values of less than -28.8 dB and -26.2 dB were achieved at 1.0 MHz for track pitches of 1.0 and 0.9μm, respectively, with a conventional optical head having an objective lens of 0.53 NA and a 780-nm laser.

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The effects of the HDDR (hydrogenation decomposition desorption recombination) phenomenon on the magnetic properties of SmFe₁₁Ti, SmFe₁₀MM′, NdFe₁₁Ti, and Nd_1+δFe₁₀MM′ (δ=0, 0.3, M=Ti, V, Mo, M′=V, Mo) compounds with ThMn₁₂-type Structure were investigated. Alloy powders of SmFe₁₀V₂, SmFe₁₀TiV, and NdFe₁₀MM′; (M=Ti, V, Mo, M′;=V, Mo) form a ThMn₁₂-type structure after heat treatment at 800°C in hydrogen and subsequently in a vacuum, but RFe₁₁Ti (R=Sm, Nd) compounds form a TbCu₇-type structure. High coercivities of 6.0 kOe and 5.8 kOe were obtained with SmFe₁₀TiV and Nd_1.3Fe₁₀VMoN_x compounds subjected to the HDDR Phenomena, respectively.

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We investigated the magnetic properties of meltspun Nd-Fe-C and Nd-Fe-C-B systems. The coercivity and (BH) _max of Fe_100-x(Nd_2/3C_1/3)_x ternary alloys (x=17.5, 20, 22.5, 25) heat-treated at 800°C increased with a decrease in the Fe content. The (BH) _max increased with the addition of boron to Fe_77.5 Nd₁₅ (C_1-zB_z)_7.5 alloys. The Nd₂Fe₁₄C phase was clearly observed in the specimens, and an unknown ferromagnetic phase also appeared. The relative intensities and positions of the peaks of Mössbauer spectra led us to conclude that C atoms occupy the same sites as B atoms in the Nd₂Fe₁₄B phase and have a similar effect. The average magnetic hyperfine field of Nd₂Fe₁₄C is around 93% of that of Nd₂Fe₁₄B.

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Ba-Zn-system W-type hexagonal ferrite magnets were prepared by a new manufacturing method in which BaO was added after semisintering treatment, and without atmosphere control. This process was found to be very useful in stabilizing the W-type hexagonal structure. The optimum conditions for making magnets, and some properties of typical specimens are as follows: chemical analysis Ba_1.092Zn_1.725Fe²⁺_0.410Fe³⁺_15.848O₂₇; semisintering condition 1275°C×1.0 h in air; sintering condition 1225°C ×0.5 h in air; magnetic and physical properties J_m=0.405T, J_r=0.364T, H_cJ=86.0kA/m, H_cB=82.0kA/m, (BH)_max=18.5 kJ/m³, T_c=330°C, H_A=987.0 kA/m, K_A=1.87×10⁵J/m³, and n_B=33.7μ_B.

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Fe-Pt alloy thin films were prepared by the RF-magnetron sputtering method. From X-ray diffraction and TEM observation, the following results were obtained: (1) the as-deposited films are disordered and consist of micrograins of about 150Å∼200Å, and (2) the annealed films are ordered and their grain size is about 400Å∼500Å. A lamellar microstructure, which is considered to be a microtwin structure, was observed within the grains. Magnetization measurements revealed that the coercive force H_c of the annealed films has amaximum (15.8kOe) at about equiatomic concentration. The origin of the high H_c is considered to be related to the microtwin structure. It was found that H_c begins to increase at an annealing temperature of 300°C, Which means that the order phase begins to grow at the same temperature. The magnetization M of the annealed films was smaller than that of the asdeposited films. The decrease in M at about equiatomic composition is ascribed to a change in the magnetic structure.

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Fe₃B-based Nd-Fe-B permanent magnetic materials containing Co and Mas additives, where M is one of Al, Si, Cu, Ga, Ag, and Au, were prepared in an extremely low-rare-earth concentration range of around 4 atomic percent. The hard magnetic properties develop as a result of a heat treatment of rapidly solidified amorphous ribbons, which produces a metastable nanocrystalline structure consisting of Fe₃B and Nd₂Fe₁₄B. Use of the additives considerably reduces the crystallite sizes, and consequently, the alloys attain higher coercivity than that obtained in alloys without the additives. Compaction-molded resin-borlded magnets produced from the Nd-Fe-B-Co-M materials have the following magnetic propertise: H_cJ=300kA/m-470kA/m, B_r=0.7 T-0.9 T, and (BH) _max=50 kJ/m³-73 kJ/m³. The typical values of the temperature coefficients of B_r and H_cJ of the bonded magnets are -0.05%/K and -0.35%/K, respectively, in the 297 K-413 K range.

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The soft magnetic properties and structures of nanocrystalline Fe-Al-Si-Nb-B alloy ribbons crystallized from an amorphous state were investigated. The best soft magnetic properties (effective permeability (at ƒ=100 kHz)=23000, core loss (at ƒ=100 kHz, B_m=0.1 T)=9(W/kg), and saturation magnetostriction, λ_s=+0.5 (×10^-6)) were obtained for Fe₆₆Al₈Si₁₄Nb₃B₉ alloy ribbons. These new alloy ribbons were composed of bcc Fe-based alloy with a grain diameter of less than 200Å. It was considered that these good soft magnetic propeties were caused by the nanocrystalline structure of Fe-Si-Al alloy.

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The magnetic properties of Zr- and B-added Supersendust (Fe-Al-Si-Ni) alloy ribbons were studied. Although the ribbons became brittle and their magnetization decreased with an increase in Zr and B addition to the Supersendust, their soft magnetic properties improved. Ribbons with ductility after melt quenching and fairly low coercivity after annealing were obtained by the addition of about 1.5 at% Zr and 8 at% B to the Supersendust. The structural change from an amorphous to a microcrystalline state led to a decrease in the magnetostriction and coercivity and an increase in the initial permeability. Microcrystalline Fe_69.7Al₇Si_9.8Ni₄Zr_1.5B₈ alloy exhibited a fairly high permeability of about 25,000.

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The effects of heat treatment on the magnetic properties of amorphous ribbons under tensile stress are studied. In this study, we focus on two properties; coercive force and the stress-magnetization change due to tensile stress. The effects on these two properties of stress relaxation by heat treatment are demonstrated, and effects on them of samples heattreated under a magnetic field are also studied.
The coercive force decreases at first when a small tensile stress is applied, but thereafter increases with the application of a larger stress. These properties can be explained by the change in the domain structure.
The magnetization change due to an applied tensile stress under a constant magnetic field can be shown to be composed of two effects, namely reversible and irreversible magnetization change.
The effects of heat treatment on these two changes are also investigated, and are also explained by the change in the domain structure.

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A change in the shape of the hysteresis curve, which arises together with a change in the measuring speed, was observed in automatic magnetic measurement of magnetic soft iron by using a ring specimen. A larger thickness of specimen, a higher annealing temperature, and a quicker measuring speed caused an increase in the apparent coercive force. It was shown that the phenomenon was caused by the delay in magnetization. The delayed magnetic flux density produced an inclination to the result of calculation based on the penetration depth of the magnetization.

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The influence of surface properties on the magnetic properties of grain-oriented silicon steel was investigated by measuring iron losses and magnetic domain patterns in an oxide-film-coated and mirror-surface-finished specimen with tensile stress in the rolling direction. When the surface roughness is reduced, the hysteresis loss falls rapidly and markedly, presumably because of the enhanced mobility of the domain wall. When the tensile stress is increased to about 10 MPa, the eddy current loss is reduced, because of the refinement of the magnetic domain, while over about 10 MPa it is reduced gradually, presumably because of the rotation of the magnetization direction.

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A heat-proof magnetic-domain-refining technique has been developed that performs well when applied to a wound-core transformer in which the iron loss suffered with non-refined material can be reduced by about 10%. The new technique is characterized by grooves introduced on the sheet surface after the final cold-rolling process.

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Thin grain-oriented silicon steels are well known to have very low iron losses. A continuous annealing method was used to obtain along (over 1m) thin grain-oriented silicon steels. As a result, thin grainoriented silicon steels 40μm thick and 1m long were obtained. The annealing temperature was 1423K and the sample speed was 0.7∼2.1mm/s. The annealing time needed to complete the recrystallization of (110)[001] grains was only a few minutes. However, the grain size of the sample was not uniform. Therefore, the magnetic properties depend on the position of the sample.

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Thin (less than 0.1mm) grain-oriented silicon steels are known to have lower iron loss than iron-based amorphous materials. It is possible to reduce the iron loss of thin grain-oriented silicon steels further by applying new magnetic-domain refining techniques. One method for magnetic-domain refining is to control the grain size. We observed the magnetic, domain and measured the iron loss of thin grain-oriented silicon steels with small (less than 1mm) grains. This experiment showed that the magnetic-domain can be made narrower by decreasing the grain size, which reduces the eddy current losses. On the other hand, materials with larger grain sizes have lower H_c and lower hysteresis losses.

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We previously reported that the estimated eddy current losses agreed comparatively well with the measured ones for very thin 3% Si-Fe strip-wound cores in the 500Hz∼5 kHz frquency region. The eddy current losses were estimated by applying domain wall numbers to a modified Pry and Bean model. We observed the domain wall numbers on the outermost surface by using an SEM. Here, in order to investigate the difference between the measured eddy current losses and the estimated ones below 500 Hz, we removed the layers of a 3%Si-Fe strip-wound core one by one and examined the relation between the domain wall numbers and the eddy current losses. In this experiment, the cross-sectional area of a strip-wound core had to be large enough to maintain a sinusoidal flux condition in core loss measurement after several numbers of layers were removed. We also examined the use of continuous annealing to fabricate along and very thin grain-oriented 3%Si-Fe strip.

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At a thickness of 30μm, thin grain-oriented silicon steel sheets have the lowest iron loss. We observed the recrystallization behavior and magnetic properties of 30μm-thick silicon steel sheets, and compared them with those of 60μm-thick silicon steel sheets. As a result, the recrystallization processes of the two types of sheet were found to be different. The primary recrystallized 30μm-thick silicon steel Sheets did not have a strong texture like that of (110) [001]. Therefore secondary recrysta11ization did not occur. However, at annealing temperatures of over 1050°C, the grain of (110) [001] grew selectively. Thus we were able to obtain very thin grain-oriented silicon steel sheets with a thickness of 30μm.

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The Fe_0.7Co_0.3 alloy has a large magnetostriction value and a high saturation magnetization. We have investigated the magnetostriction and magnetic properties of bcc Fe-Co-RE (RE: rare earth elements). These films were prepared by DC triode sputtering method. An addition of the RE elements Pr and Tb Were found to increase the magnetostriction value, while the addition of RE elements Ce, Nd, Sm and Er decreased it. These alloy films all exhibited a high saturation magnetization value, greater than 200 emu/g. This occured upon an addition of a small percentage of the RE element. These films may be useful as soft magnetic materials.

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The effects of compressive stress on the magnetization in grain-oriented silicon iron sheets have been investigated. The magnetization changes due to compression are composed of two effects, reversible and irreversible magnetization changes. The magnetization changes due to compression for a sample cut at a declining angle of 35° from the rolling direction have peculiar characteristics. This sample shows two peaks of magnetization change due to compression. Changes in the domain structure due to compression were observed in order to determine the mechanism of magnetization change. A stripe domain pattern with 180° domain walls changes into a small perpendicular stripe pattern as a result of the application of both a magnetic field and compression, and the density of stripes changes as a result of compressive stress.

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The domain structure and high-frequency response of magnetization for amorphous soft magnetic CoNbZr films were studied, using the Bitter method and scanning Kerr-effect microscopy. A Lifshitz-type domain structure characterized by wedge-shaped domains was observed in the films (with a stripe-width of over 100μm and a thickness of 1μm). The changing magnetization associated with the 180° domain wall movement increased with increase in frequency, and reached a maximum at around 5∼10 MHz, while, the changing magnetization at the wall of the wedge-shaped domain or at the 90° domain wall showed a maximum around 30 MHz. The loss factors due to these magetization changes were 3 to 6 times that due to the rotation of magnetization at frequencies ranging from 20 MHz to 40 MHz. These results imply that the change in magnetiztion due to the wedge-shaped and 90° domain walls exert some influence on the Q factor of the thin-film inductor at high frequencies above 10 MHz.

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This paper glves a numercial expression of power losses at high frequencies (100kHz∼2MHz) in Mn-Zn ferrites. which are used as core materials of transformers and inductors for switching power supply. The power losses of some commercial ferrites were measured, and a new type of empirical formula was found, which is expressed as a function of frequency and magnetic flux density. The calculated results agree well with the measured ones. The formula is useful in the design of compact and effcient magnetic components.

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The Ar thin-film deposition process of a Lennard-Jones system was studied by introducing a rapid quenching process into a molecular-dynamics method. About five layers of Ar atoms were deposited at a very low substrate temperature of 1 K. The atomic distribution of the film had characterisitcs of an amorphous structure and also showed an exotic anisotropy. The nearest-neighbor atoms were located closer in the horizontal film planes than in a plane orthogonal to the film. This type of anelastic deformation of the atomic environment in the film is discussed with relation to a perpendicular magnetic anisotropy that has been noticed in an amorphous rare earth-transition metal alloy film.

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The atomic structure and magnetic properties of melt-quenched Sm_100-xFe_x (x=1, 10, 20, 30, and 40) alloys were studied by means of X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. For x=10, 20, 30, and 40, clusters of amorphous Sm-Fe phases are formed in an hcp-Sm matrix, and some of them behave superparamagnetically. In the thermomagnetic curves for x=10, 20, and 30, a field cooling effect was observed at temperatures less than around 160 K, which is the magnetic transition temperature of pure hcp-Sm. This effect is due to inter-cluster interaction induced by magnetic ordering in the hcp-Sm matrix. For x=1, Fe atoms are dissolved in the Sm matrix and their magnetic moments are very small.

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The magnetic properties of Fe-Tb-B alloys with TbFe₂, finely crystallized from an amorphous state were in vestigated. The amorphous samples with the composition of more than 5 mol% B, which are situated on the connected line between Fe₂Tb and FeB, were prepared by rapid-quenching. An amorphous Fe₆₅Tb₃₀B₅ alloy began to crystallize into a single phase of TbFe₂ at 803 K, and a microstructure with a grain size of about 10nm was obtained by heating at this crystallization temperatutre for 1 hour. The fine TbFe₂phase lowered the coercive force. Substitution of 5 mol% Mo in Fe₆₅Tb₃₀B₅ led to the smaller grain size and also lower coercive force. On the other hand, the magnetostriction of Fe-Tb-B alloys at an applied field of 1.28 MA/m was increased by replacing Fe by 5 mol% Ti or 5 mol% Cr.

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The magnetostriction of rapidly quenched Tb (Fe_1-xM_x)₂ alloys with M=Co, Ni, Mn, Cr, Ti, V was investigated at room temperature. The values of λ_s at low content of x (x=0.05 for M=Ti, V, Mn, Ni, x=0.1 for M=Cr, x=0.2 for Co) were 1500∼1700×10^-6 and did not show an appreciable dependence on M elements. Above x ≥0.1λ_s values decrases rapidly with anincreasein the M content for M=Ti, V, Cr. The magnetic sofness was evaluated from the magnetostriction at remanence (λ_R) and the magnetic softness parameter H′_c. The Tb(Fe_0.9Mn_0.1)₂ a1loy shows the best magnetostriction property, where the values ofλ_s, λ _R and H′_c were 1400×10^-6, 620×10^-6, 24 kA/m, respectively.

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The ternary R₂T₁₇-type alloys Dy₂Fe_17-x-yAl_x with Fe deficiency have been studied by means of X-ray diffraction and magnetization measurements. The single phase boundary of R₂T₁₇-type structure was determined to be near the composition Dy₂Fe₉Al_x for x≥4 and Dy₂Fe_13-xAl_x for x≤4. The crystal structures are of the Th₂Ni₁₇-type for alloys with x≤5 while a Th₂Zn₁₇-type for those with 6≤x≤8. The thermo-magnetic curves show that the magnetism varies from P-type to N-type ferri-magnetism with an increase in the Al content x. Three types of spin arrangements, in which x≤2, 2<x≤5, 6≤x≤8, were proposed on the basis of the magnetic studies. It was concluded that the substitution of Al for Fe causes a derease in the Fe magnetic moment, but that defects in the Fe cause an increase in the Fe magnetic moment.

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The study of magnetic domain-wall motion is important in the fields of both power-magnetic micro-cores and magnetic recording applications. The nonlinear differential equation of the Bloch wall motion is obtained by modification of the Landau-Lifshitz-Gilbert equation. The terms of the non-linear force of restitution and eddy current damping are added, and the equation is solved by using the fourth Runge-Kutta method. The tendency for the amplitude of magnetic domain-wall motion to decrease with an increase in the frequency of the CoZrMo/SiO₂ multilayered core is reproduced well by computer simulation. The irregular oscillation of the domain wall is found to be chaotic because a fractal structure is observed in the Poincaré map. This result leads to a method for investigating energy loss and irregular phenomena (error or noise in magnetic recording systems) arising from magnetic domain-wall oscillation.

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The effects of adding Al to sputtered nanocrystalline Fe-Ta-C films on the structure, soft magnetic properties, and corrosion resistance of the films were investigated. The films were crystallized from an amorphous state to a nanocrystalline state in which ultrafine TaC particles were dispersed. Most of the Al in the films was dissolved in α-Fe after crystallization. When the Al concentration was increased, the high-frequency permeability improved owing to the increase in electrical resistivity. The thermal stability of the soft magnetic properties also became higher than that in Fe-Ta-C films, and the corrosion resistance of the films improved sufficiently probably because of the dissolved Alin α-Fe. An Fe_66.6Al_10.6Ta_10.5C_12.3 nanocrystalline film after annealing at 823K exhibited a high saturation magnetization of 1.25T, a high permeability of 3200 at 1 MHz, a high electrical resistivity of 1.32μΩ·m, and excellent corrosion resistance and noble pitting potential.

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We examined the magnetostriction and coercive force of amorphous Tb-Fe films while varying the sputtering conditions (rf input power, Ar gas pressure, Tb content, and so on). Here we discuss the possibility of obtaining both soft magnetic properties and large magnetostrictionin this system. Soft magnetic properties and large magnetostriction were obtained simultaneously in sputtered Tb-Fe thin films prepared with a composition of 45∼50 at% Tb-Fe. Ar gas pressure of 4 mTorr, and rf power of 200 W. This material has astrong potential for use in magnetomechanical thin-film devices.

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The magnetostriction and magnetic properties of sputtered Sm_xFe_100-x (3≤x≤54) thin films were investigated at room temperature. The films have amorphous structure at x≥12. The magnetostriction (-λ) of these films increased rapidly in low fields (<1 kOe) and reached maximum values of 130-160×10^-6 at 16 kOe for x=30-40, suggesting that Sm-Fe films could be used for micro-actuators and sensors. The magnetic properties did not show clear dependence on the sputtering conditions, such as input power, Ar gas pressure, and substrate temperature (≤250°C).

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