The effect of heat-treatment on magnetic properties and microstructure of electroless CoNiP films for perpendicular magnetic recording media was investigated in order to clarify the microstructure in as-deposited conditions, as well as to evaluate their thermal stability. The as-deposited film consisted of a mixture of <002> perpendicularly oriented hcp structure and fcc structure without obvious crystal orientation. The heat-treatment higher than 400°C altered the crystal structure from the domination of the hcp structure into that of the fcc structure. The crystallites grow larger with the heat-treatment, causing a sharp change in the magnetic properties. These changes were due to the disappearance of magnetocrystalline anisotropy induced by the cobalt hcp structure, and the decrease in the shape magnetic anisotropy due to the change in film topology. On the basis of these results. it was suggested that a compositional inhomogeneity due to a segregation of Co-rich region existed in the as-deposited films; then such segregated conditions disappeared by the heattreatment, thus the crystal property of the film changed into the fcc one.

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There have been four technical problems to be solved for the commercialization of the Co-Cr video floppy disk (VFD): 1. smooth headtouch 2. durability and reliability under various environmental conditions 3. significant improvement of recording performance 4. reasonable cost. This paper shows that it will be feasible to solve 1 and 3 simultaneously. Regarding 2, durability has been achieved at 23°C, 50%RH and 40°C, 80%RH. It is also confirmed that, by using a narrow track with 10 μm width which is 1/6 of the track width (60 μm) used in the ordinary MP-VFD playback, a comparable video image can be obtained.

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A new sputtering source (named SPT target) was modified to realize a high-rate deposition and continuous fabrication of Co-Cr composite perpendicular recording media. In order to improve orientation and crystallinity of Co-Cr layer and Permalloy backlayer, the aperture position was optimized and the magnetic return path plate was added to the target. The Co-Cr tape medium deposited on a 9μm thick polyimide film by using this modified sputtering source showed good high-density recording performance.

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In order to improve the anisotropy field distribution of Co-Cr layer, the effect of Ta addition into a Co-Cr recording layer was investigated. It was found that by the Ta addition, the initial Co-Cr layer with poor crystalline orientation was eliminated, and the crystalline orientation and the crystallinity were drastically improved. It was also confirmed that the anisotropy field distribution of the Co-Cr-Ta layer was narrowed to one-third of the Co-Cr layer. To clarify the effect of Ta addition on recording characteristics, Co-Cr-Ta/Nb-Permalloy double-layer media were prepared and their recording characteristics were measured. The Co-Cr-Ta media showed a sharp magnetization distribution and higher reproduced voltage at high densities than did the Co-Cr media.

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A new texturing method for glass disk substrates is proposed. Thin perforated plastic film (microgrid) is first formed on a substrate, and then the substrate is chemically etched using the perforated film as a mask. The textured substrate has micro round holes distributed uniformly on the surface. A 0.2 μm thick magnetic film and 0.025 μm thick carbon overcoat were sputter-deposited on the textured substrate and CSS tests were carried out using a Al₂O₃-TiC minislider head. The microgrid-textured disk of 3 μm hole diameter and of 0.1 μm hole depth showed a good friction coefficient as low as 0.4 after 25600 CSS cycles. This result is better than that of a mechanically textured disk of similar surface roughness.

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In fabricating Co-Cr films with a continuous vacuum deposition system, incident angle of vapor beam onto substrates affects magnetic properties and recording characteristics of the films. The Co-Cr films deposited with incident angle from 55° to 20° and from 70° to 20° are anisotropic and the films deposited with incident angle from 20° to −20° are isotropic in the film plane. Azimuth angle dependence of reproduced output in these films fairly coincides with angular dependence of M_r, in the film plane. Isolated waveform of the films deposited with incident angle from 55° to 20° has MMF dependence in normal head scanning direction, while in the films deposited with incident angle from 70° to 20° it is independent of MMF either in normal or reverse head scanning direction.

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Using ⁵⁹Co nuclear magnetic resonance and a chemical etching technique, we observed that compositional separation which produces highly Co-rich precipitates occurs in (1) a Co-Cr film which exhibited ultra-high bit density in perpendicular magnetic recording and (2) Co-Cr-X (X=Ta, Pt, Ni) films for longitudinal magnetic recording. It is expected that this kind of separation will enable the compositional microstructure of Co-Cr based alloy films to be changed from a homogeneous structure to a particulate one suitable for either perpendicular or longitudinal high-density recording.

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The behavior of noise-after-write in thin film heads was studied. The probability of noise-after-write events was decreased by applying a constant amplitude current or a decay amplitude current to the head coil, after shutting off a recording current. A constant amplitude current has a higher ability to decrease noise-after-write than a decay amplitude current.
Comparison between the noise pulse of a Ni-Fe head and that of a Co-Ta-Zr amorphous head shows that the former head has a wider pulse width than the latter head.

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The magnetization response of thin-film heads in the high frequency region was studied using the Scanning Kerr Effect Microscope. The area of large magnetization rotation converges gradually to the center portion of the core of a thin-film head as the frequency is increased. Over 20 MHz, the domain structure changes; i.e., the number of domains increases with increase in frequency and the curvature of both sides of the 180° walls becomes gradually small. In result, the convergence region of the magnetization rotation becomes wider. Compared with the static magnetization direction and the magnetization response, at the high frequency the magntization along the track direction in static rotates large, while that slanted from the track direction rotates small.

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Dependence of field gradient on media noise was demonstrated. Medium noise was worsened by influence of secondary field, when the field gradient of the secondary field is considered to be the dullest one. The influence was confirmed by the investigation of change of media noise, which is based on the intrinsic micromagnetic media properties, against different field gradients. Reverse DC modulation noise and transition noise of low H_c and high H_c disks were evaluated by using a single sided MIG and a ferrite mini-monolithic head. The reverse DC modulation noises showed a different value for each head in spite of the same medium. The increasing ratio of the reverse DC demagnetized noise to the DC saturated noise, i. e., reverse DC modulation ratio, showed higher value when the medium was evaluated by using the MIG head which can generate a sharper field gradient in each medium. However, the transition noise was smaller by using the MIG head than by using the ferrite head. As a result, both the reverse DC modulation increasing ratio and the transition noise level which was believed to be an intrinsic property of media were strongly correlated to the field gradient.

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An operating point model has been proposed to determine dependence of output on the head-to-medium spacing in a single-pole head and CoCr/NiFe double-layer medium system. We studied this dependence for various CoCr thicknesses and compared the experimental results with the analysis using this model. For each medium, the linear dependence changed at a specific spacing. Magnetic flux density at the operating point is proportional to permeance factor, P_r and P_r/(1+P_r) as the spacing changes. The theoretical values agreed well with experiments.

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CoPtB-O films show a large perpendicular magnetic anisotropy and coercivity with a high saturation magnetization. Therefore, CoPtB-O films are promising for high density and high output media. Recording characteristics of CoPtB-O perpendicular recording media were investigated. CoPtB-O films were prepared by rf sputtering on glass substrates for hard disk, and recording characteristics were measured by using a MIG type ring head for VTR's with a spring suspended mechanism. A large reproduced output was obtained at 7.87 Mfc/m {200 kFCI} using a head with proper gap length of 0.35μm. To obtain a large reproduced output at a high recording density, it is necessary to use medium with a large perpendicular coercivity and a perpendicular anisotropy, and to choose proper head gap length according to the recording wave length.

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Temperature dependences of magnetic properties and Kerr spectra of MnBi and MnBiAl films below room temperature were investigated. It was found that the saturation magnetization increases about 5% and the Kerr rotation at wavelength 700 nm increases about 20% for MnBi film when the temperature is decreased from 300 to 80 K. No obvious influence on magnetic properties and no apparent variation in Kerr spectrum can be observed after doping of 5%Al in MnBi films.

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Magneto-optical disks with Co/Pt multilayered films an RF-etched SiN underlayers were prepared. Thermomagnetic writing experiments showed that RF-etching of SIN reduces playback noise by 4 dB. We have achieved a C/N ratio of 58 dB under conditions of linear velocity. 11.3 m/s; recording frequency, 1 MHz; reading laser power, 1.2 mW; and resolution bandwidth, 30 kHz. Results of measurements of XRD and magnetic properties for Co/Pt Aims on both unetched and etched SiN suggest that noise reduction by etching of SiN underlayer comes from the better crystallographical <111> orientation perpendicular to film surface.

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Kerr ellipticity angle γ_k of TbFeCo film and its influence on the rnagneto-optical responses of magneto-optical media were investigated. The γ_k was derived through wavelength range of 400∼830 nm by a simple method which adjusts the calculated value of Kerr rotation angle to match with the measured one by varying γ_k. Kerr ellipticity angle γ_k of the TbFeCo film increased with shortening of the wavelength, although Kerr rotation angle θ_k decreased. Contribution of θ_k and that of γ_k to the Kerr rotation angle of the films with enhancing structure could be separated and were found to be additive and the latter one was more dominant at the shorter wavelength. It was also shown that the maximum value of the figure of merit of 4-layer medium is enhanced by the contribution from the γ_k.

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Rewritable compact discs (CDs) using magnetooptical (MO) materials have been developed. The disks were prepared by depositing Si₃N₄, TbFeCo alloy, Si₃N₄ and Al films on polycarbonate substrates utilizing a rnagnetron sputtering system. Sputter etching was carried out for Si₃N₄, under-layer of magnetic layer, with the very interesting effect of improvement of the external magnetic field sensitivity. Stabilities on write power and magnetic field sensitivity for the above MO disks were investigated. In this paper, the relation between recording sensitivity stability and the sputter etching effect is reported.

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Compression bonded magnets were manufactured using melt-spun ribbons of Nd₁₁Fe₇₂Co₈B_7.5V_1.5, MQP-B and MQP-D (GM Co., Ltd.). The magnetic field and temperature dependences of the magnetic aftereffect constant (S_V) which decided the magnetic stability, were studied. Compared with the bonded magnets using MQ powders, Nd₁₁Fe₇₂Co₈B_7.5V_1.5 bonded magnet had larger (BH)_max, but smaller S_V (2.3 kA/m). The temperature dependence of S_V for Nd₁₁Fe₇₂Co₈B_7.5V_1.5 bonded magnet was better than that of Nd-Fe-B sintered magnets. The activation volume (v) at room temperature, of Nd-Fe-Co-B-V, MQP-B and MQP-D bonded magnets was approximately 18×10^-25, 15×10^-25 and 18×10^-25 m³, respectively. The relation among H_cJ, S_V and v, namely, Barbier plot, was studied for these Nd-Fe-B system compression bonded magnets, as well as for Sm₂Co₁₇ sintered magnets and Sm₂Co₁₇ system compression bonded magnet whose mechanism of magnetization reversal are the same pinning-type. From the results of Barbier plots, it was found that the relation between In S_V and In H_cJ was straight line, and H_cJ was in proportion to v^-0.6.

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A new manufacturing process for extrusion molded magnets, composed of isotropic Nd-Fe-B powder and Nylon-12, has been developed. This newly developed extrusion molding process has several interesting features. First, the extruded product contains 72% by volume magnetic powder and yields a (BH)_max, of 8.0 MGOe. Second, through the addition of an anti-oxidant, the viscosity of the magnetic powder-nylon compound during molding remains almost constant. Third, by means of a specially cooled outlet, which is separated from the heated die by a thermal insulator, an optimized temperature profile is obtained which yields uniformly smooth extrusion molded magnets. Both long thin-walled magnets and small arc-shaped (“kawala”) magnets are easily molded by this new process.

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Anisotropic Nd-Fe-B-Cu powder was fabricated by grinding melt-spun and subsequently hot-rolled materials. We prepared two types of powder with different particle shapes: one in anisotropic shape and the other in a flat shape with c-axis perpendicu. lar to the flat face. Perpendicular-field pressing experiments show that the isotropic particle is better aligned in the bonded magnet than the flat particle. Radial-field pressing using the isotropic particle gives a high (BH)_max, value up to 16 MGOe for bonded magnets with density of 6.0 g/cm³.
The Nd-Fe-B-Cu powder has been found to be well aligned in a relatively low magnetic field. This fact is beneficial for fabricating ring magnets with smaller radius or larger height.

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Relationship between magnetizability and grain size was investigated in Nd-Dy-Fe-Co-B-M (M=V or MO) sintered permanent magnets. Grain size distribution was measured by using a high speed image processor. It has been confirmed that addition of V or Mo results in a decrease in the average grain size and grain size distribution. Dependence of the relative open flux on the magnetizing force in these magnets revealed that a small grain is essential to obtain a good magnetizability and an enhanced coercivity. It is suggested that the local demagnetization field decreases when grain size decreases, leading to improvements both in magnetizability and coercivity of V or Mo-added Nd-Fe-B sintered magnets.

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We have applied multi-pass packed-rolling to producing anisotropic Nd-Fe-B-Cu powders from rapidly-quenched ribbons. Analysis for the packed-rolling process shows that densification proceeds from the surface of the packed powder-compact and crystallographic alignment proceeds more rapidly at the center. Rolling with ribbon-thickness reduction higher than 80% produces a uniform material with a high (BH)_max, up to 38 MGOe. The present paper discusses the alignment mechanism considering internal-stress distribution inside the powder-compact under rolling pressure.

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Sm₂Fe₁₇N_x (x=3) of 95 vol% purity was obtained by nitrogenation of Sm₂Fe₁₇ alloy using a mixed-gas of NH₃ (0.35 atm) and H₂ (0.65 atm). The saturation magnetization, 4πI_s, was 15.5 kG, and the anisotropy field, H_a, was found to be 220 kOe. Aligned powders of Sm₂Fe₁₇N₃ having an aver age grain size of 3 μm showed the (BH)_max, value of 35 MGOe on the assumption that the powder was compressed into full density. The effects of the presence of nonnitrogenated phase and SmFe₃N_y phase on magnetic properties of compressed powder magnets are also discussed.

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The effects of nitrogenation on the magnetic properties of Sm₂(Fe_0.9M_0.1)₁₇C_1.6 (M=Ga, Cr) melt-spun ribbons were studied. The melt-spun amorphous ribbons were crystallized at above 550°C in forming TbCu₇ phase, and they were further transformed to Th₂Zn₁₇ phase above 680°C on heating. The nitrogenation at 550°C for 4 h enhances the magnetic properties of annealed ribbons. The Sm₂(Fe_0.9Cr_0.1)₁₇C_1.6 ribbon annealed at 650°C which consists of TbCu₇ phase, exhibits high (BH)_max, of 11.0 MGOe after nitrogenation. The Sm₂(Fe_0.9Cr_0.1)₁₇C_1.6 ribbon annealed at 725°C. which consists of Th₂Zn₁₇ phase, shows high coercivity of 19.0 kOe with (BH)_max, of 7.4 MGOe after nitrogenation.

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This paper describes the use of hydrogen in the processing of Sm₂Fe₁₇N_x powders with good coercivity. The hydrogen absorption and desorption behavior of Sm₂Fe₁₇ compound were studied. The green compacts of Sm₂Fe₁₇ compound were heattreated in hydrogen at around 600∼1000°C, in decomposing into α-Fe and samarium hydrides. They underwent further dehydrogenation by alternating the heating atmosphere into a vacuum, resulting in the reforming Sm₂Fe₁₇ phase.

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Experiments were carried out to investigate the Co substitution on the magnetic and physical properties of Sm₂Fe₁₇ nitriding compouds. Sm₂(Fe_1-xCo_x)₁₇ nitriding compounds (x=0∼0.3) were prepared by heat treating fine powders of Sm₂(Fe_1-xCo_x)₁₇ alloys in the pressure of 4.9 MPa N₂ gas. From X-ray diffraction patterns, these nitriding compounds were the Th₂Zn₁₇-type structure. Sm₂(Fe_1-xCo_x)₁₇ alloys were observed to absorb the same large amount of nitrogen as Sm₂Fe₁₇ alloy. Curie temperature of these nitriding compounds increases with increasing the Co content, and lattice parameter (a and c) decrease a little. The intrinsic coercivity of 652.5 kA/m (8.20 kOe) and Curie temperature of 556°C were achieved with Sm₂(Fe_0.8Co_0.2)₁₇N_3.1 compounds.

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Soft magnetic ferrites now in use as magnetic devices have a disadvantage in that the saturation magnetization is considerably lower than that of metallic soft magnetic materials. The present authors found that the Mn-Zn ferrite single crystals containing about 0.05 mol% Er₂O₃ have improved saturation magnetization (σ_s) and relative permeability (μ'_s). It is considered that the effect of the Er₂O₃ addition on magnetic properties is closely related to the increase of saturation magnetic moment by the dissolving of Er into the Mn-Zn ferrite. Mn-Zn ferrite containing Er₂O₃ is expected to be useful as a magnetic head material.

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Grain diameter and magnetic properties of rapidly quenched Fe-M-Si-Ge (M=Ti, V, Zr, Nb, Ta) and Fe-Hf-Cu alloy ribbons were investigated. The grain size of Fe-Ta-Si-Ge alloys decreases rapidly from 2700Å to about 400Å with the addition of Ta up to 3 at%. Coercivity increases rapidly from 2.3 to 30 Oe with the increase of Ta content. For Fe-M-Si-Ge alloy systems, the decreasing of grain diameter and the increasing of coercivity with the addition of M are in order of Ta, Nb, Zr, Ti and V. The grain diameter of Fe-Hf-Cu alloys decreases to about 600Å with the increase of Hf content to 4∼6 at%. The coercivity increases to about 20 Oe with increasing Hf content. Coercivity of these rapidly quenched Fe-based alloys is roughly proportional to the inverse of grain diameter.

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Crystal structures and magnetic properties of (Fe_0.6Co_0.4)_100-XM_X (M= Ti, V, Zr, Nb, Y, Cu, Pt, Al, Si, Ge; X=0∼10) alloys annealed at 900°C were investigated. The crystal structures are b. c. c. for M= V, Nb, Y, Cu, Pt, a mixture of b. c. c. and f. c. c. for M= Ge, X= 2∼4, and b. c. c. plus unidentified structures for M=Ti, Zr. The saturation magnetic flux density B_s decreases extremely for M=Ti, Nb. Ge, decreased slightly for M=Al, Si and remains unchanged for M =Pt. The saturation magnetostriction increases up to∼10^-4 for M=Pt, increases slightly for M=Cu, Ti, Zr, X=2 and decreases slightly for other M elements. The saturation magnetostriction constants λ_s are roughly proportional to B₂^s.

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The hydriding property of DyFe₂ alloy was examined with respect to the pressure-composition-temperature (P-C-T) relation and the pulverization behavior. The isotherm measured at 300 K suggests the formations of DyFe₂H₃ and/or DyFe₂H₄. The dissociation pressures of this hydride lie at 0.03 kg/cm² at 300 K. Block samples of DyFe₂ were found to be pulverized even after one hydriding-dehydriding reaction. The particle size of the DyFe₂ powder can be controlled by changing the number of the cyclic hydriding-dehydriding reaciton.

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The anisotropic magnetoresistance (Δρ, ρ₀ and Δρ/ρ₀), the ordinary Hall coefficient (R₀), the extraordinary Hall coefficient (R_s) and the saturation magnetization (M_s) were measured for Ni-Co, Ni-Fe and Ni-Cu binary alloy thin films in the range from 77 K to 300 K. As a result, the increase of Δρ and Δρ/ρ₀ corresponds well to the minimum R₀ ranged from −1.0 to −2.0×10^-12 Vcm/AOe and nearly equal zero R_s. It is highly similar to the correlation for Ni-Fe-M alloy thin films at 300 K. Within the present alloy system, R_s(T) is empirically represented as C{ρ₀(T)/ρ₀ (77)}ⁿ. N is given as 0.8∼2.4 and C is −12.0∼0.5×10^-10 Vcm/AG, which is nearly equal to R_s(77). The increase of Δρ/ρ₀ corresponds well to the decrement of absolute value of the coefficient C. The maximum of Δρ/ρ₀ was found to be obtained around zero value of C.

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Magnetoresistance was studied for circular and width-varied rectangular Ni-Co-Fe ternary alloy thin films. Resistivity was measured using fourpoint prove. Applying the method of images, the true value of ρ_av can be obtained on every film. But that of Δρ cannot, because the angle between the current direction and magnetization direction is not uniform in the film. The behavior of ρ_av and Δρ can be understood exactly by the finite element method, allowing the magnetoresistance of variously shaped films to be analyzed by it.

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Magnetic properties of amorphous Fe_100-XGd_X (18≤X≤70) alloys were prepared by melt-quenching and analyzed by molecular field theory with twosublattice model. Spin structure is of simple ferrimagnetic ordering and the moment of Fe has about 2 μ_B with wide concentration range, which is conspicuously in contrast to that of amorphous thin film. Curie temperatures were higher than those for the thin films by about 60∼100 degrees. The temperature dependence of the magnetization can be fitted by the molecular field theory with three exchange constants as the fitting parameters. The results are discussed for concentration dependence of exchange parameters in comparison with thin film case.

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Magnetization of amorphous ribbon changes due to application of tensile stress under magnetic field, and it also shows hysteresis due to tension. The change of magnetization due to tension is composed of two effects: one a reversible magnetization change and the other an irreversible magnetization change. We discuss, in this paper, characteristics of these two effects at various points on B-H curves of amorphous ribbons. The reversible magnetization change shows peak value due to applied field and it shows different values for both sides of B-H curve at the same field. This can be explained by the deformation of 90° domains. The irreversible magnetization change for lower side of B-H curve shows maximum value and this corresponds to the characteristics of differential permeability of B-H curve. The irreversible change for upper side of B-H curve changes its value from negative to positive value. This can be explained by the displacement of 180° domain wall.

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Effect of tensile stress on the magnetization properties of silicon steel sheet samples declined from rolling direction was investigated. Magnetization for B₈ showed minimum value at the angle of 55°, which is <111> direction. Reversible and irreversible magnetization change due to tensile stress was also measured for samples at various angles from rolling direction. The reversible magnetization change due to angle shows no differences among samples at low magnetic field. The differences only appear at high field. The reversible magnetization change shows peak value at the angle of 55°, which corresponds to the minimum value of magnetization for B₈. The differential magnetization change with respect to tension, which indicates the ease of movement of domain wall, shows almost similar characteristics with the reversible magnetization change. The domain structure for the sample changes drastically due to tension when the angle is increased beyond 60°.

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Magnetostriction of polycrystalline RCo₃ compounds (R =Pr, Nd, Gd, Tb, Dy) was measured in the temperature range from 77 K to 350 K. The values of λ_//-λ_⊥ at T=77K and H=20 kOe were 40×10^-6 R=Pr, 1080×10^-6 for Nd, 80×10^-6 for Gd, 2680×10^-6 for Tb and 780×10^-6 for Dy. The sign of λ_//-λ_⊥ at H=20 kOe for DyCo₃ changes from negative to positive at about 170 K with increasing temperature. The dependence of the magnetostriction on R elements in RCo₃ compounds is discussed based on the point-charge model.

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The characteristics of ferromagnetic metal nitride thin films were studied as a magneto-optical recording medium by using ion-beam sputtering. Especially the factor of perpendicular magnetic anisotropy was studied. The transmittance of the films was found to be related to c-axis orientation of the Fe and FeCo nitride. The FeCo nitride thin films were found to have a large value of the Faraday rotation θ=7.7 deg/μm at 780 nm. The Fe and FeCo nitride thin films were found to have high corrosion-resistance in a NaCl water solution. In cross section of ferromagnetic metal nitride thin film, the microstructure was observed by TEM to be a columnar structure composed of amorphous phase and crystalline phase about 10 nm or fess in diameter.

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By irradiating glass substrate with an Ar-laser (λ=514.5 nm) beams, Fe₃O₄ films were deposited in an aqueous solution at a rate as high as 2.35 μm/min. By synchronously moving substrate while plating. we successfully drew a pattern (roman letters and dots) of Fe₃O₄ film by selected area growth without using any masks. This technique is useful for fabricating fine-patterned film devices (e.g., microwave circulators and isolators) using as substrate such non-heat-resistant materials as GaAs ICs.

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Fe thin films were deposited on glass substrate using a pulsed Nd-YAG laser (λ= 1.06 μm, τ=250 μs). SEM observation showed that these films were mainly formed with fine crystallites less than 200Å, and there scatteringly existed macroscopic particles of which size depended on energy density. The streak image of plume using image converter camera showed that most of ablated particles concerned with film formation, had a velocity of more than 10⁴ cm/s. Saturation magnetic moment of the film was very close to bulk value and perpendicular magnetic anisotropy was not observed through torque measurement.

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Gas-flow-sputtering (GFS) method, in which atoms having very low kinetic energies (<0.1 eV) are deposited, was studied to grow single crystal α-Fe films on MgO(001). These films were characterized by reflection high-energy electron diffraction, X-ray diffraction and Kerr-effect magnetometry. The results suggested that single crystal Fe films were deposited at a substrate temperature of about 400°C, a growth rate of 1100Å/min and a pressure of 1 Torr.

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Magnetostriction and magnetic properties of bcc Fe-Co-Sm alloys produced by DC triode sputtering method were investigated. An addition of 3 at% Sm suppressed large positive magnetostriction of bcc Fe-Co alloys, resulting in almost zero magnetostriction in the vicinity of bcc Fe_0.7C_0.3 alloys. These nonmagnetostrictive alloys show a high saturation magnetization of about 210 emu/g, and thus are thought to be useful for soft magnetic materials.

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Soft magnetic properties of sputtered FeZrB films are investigated with additives of Co, Ni, Cr, and V. While FeZrB ternary films did not exhibit soft magnetic properties in our experiment, a few percent of additives make permeability high enough for magnetic head applications. These changes correspond to the variation of magnetostriction of the films. Any additive mentioned above makes magnetostriction constant positive from negative value of FeZrB film. However, the effects of Co or Ni addition on crystallization are different from those of Cr or V addition. By addition of Co or Ni, crystallization temperature (T_x) becomes lower, lattice spacing (L_s) larger. and saturation magnetic flux density (B_s) higher, while Cr or V makes T_x higher, L_s smaller, and B_s lower. In the aspect of soft magnetic properties, Co is the best additive of the four elements, and Fe_87.6Co_3.2Zr_5.8B_3.3 exhibits excellent soft magnetic properties after annealing at 550°C (B_s∼18 kG, μ∼5000).

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It has become clear that internal stress (σ) for thermal treated Sendust films is changed by treatment temperature, thermal expansion coefficient (α) for substrates and oxygen content in the film. Measured α value for low oxygen content Sendust film is 169×10^-7. Calculated σ values, by using the α value of the Senduct film, show good agreenent with measured ones.

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Co-Fe-B-F amorphous and nanocrystalline films were prepared by a high deposition rate sputtering apparatus with two opposing targets. The chemical composition of these films can be easily varied from (high B and low F) to (low B and high F) by changing the quantity of the fluorine gas. Futhermore, the content of metalloid (B+F) was found to be kept constant in amorphous structure. Soft magnetic properties were obtained for films with high B and low F content. These films had both high saturated magnetization of 1.6∼1.8 Tesla and high resistivity of 150∼1000 μΩcm. TEM observation clarified that F element decreased the size of nanocrystalline diameter from 10 nm to 5 nm in CoFeBF films with low B. The coexistence of both high B_s and high ρ is attributed to various factors of amorphous phases, constant metalloid contents of (B+F) and fine mixed phases by F element.

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Structural and soft magnetic properties of (Fe_1-xSi_x)-Hf-C films (0 ≤ x ≤ 0.27) crystallized from amorphous state were investigated as functions of Si concentration. They crystallize as nanocrystalline in which ultrafine HfC particles are dispersed. Most of the Si in the films is dissolved in bcc-Fe after crystallization. By increasing the Si concentration to x= 0.13, the thermal stability of the soft magnetic properties becomes 50 K higher than that of the Fe-Hf-C films. Moreover, high frequency permeability has been improved owing to the increase in electrical resistivity by 4 to 5 fold. Sufficiently high saturation magnetization of 1.3 T was obtained even when x is 0.13. For the films with x larger than 0.15, good soft magnetic properties could not be obtained probably because of the stress induced anisotropy and the coexistence of an amorphous phase with low Curie temperature.

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Gases emerging from Fe-Zr-N films with various compositions during heating were analyzed by thermal desorption spectroscopy. Their structures and magnetic properties were also investigated. H₂, N₂ and Ar were detected at 300∼400°C, 500°C and 650°C, respectively. Higher amounts of N₂ were detected from films which contained higher amounts of N₂. The composition of films changed because of emergent N₂ is as follows. The composition changed from N/Zr > 1 to N/Zr∼1, but was unchanged in the case of N/Zr ≤ 1. (100) preferred orientation occurred in films in which composition was N∼Zr > 8 (at%) at as-made while (110) or random orientation occurred in the case outside of that. In the former conditions, Fe-Zr-N films showed excellent soft magnetic properties and thermal stability up to 700°C.

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The effects of N addition into Fe-Hf-O sputtered films on magnetic properties and structure were investigated. The addition of N to Fe_93∼88Hf_2∼3O_5∼9 thin films was found ta decrease the coercivities (H_c) both at as-deposited state and after annealing at 773 K∼873 K because of decreasing grain size of α-Fe (bee phase). In particular, Fe_85.1Hf_2.1O_5.5N_7.3 films composed of phase with fine grain of about 150Å, γ'Fe₄N and Hafnium Oxide Nitride, exhibited low coercivity of 64 A/m and high saturation magnetization (B_s) of about 1.7 T even after annealing at 873 K. Thus, this thin film with high B_s. low H_c and high thermal stability is expected to be used as magnetic head materials.

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Magnetic and structural properties of multilayered FeN /FeBN films prepared with dual-type sputtering were investigated. Laminating the FeBN films with FeN films increases the electrical resistivity (R) up to 200 μΩcm. decreases slightly the saturation magnetization and shows excellent soft magnetic properties (coercivity ≤ 0.2 Oe and permeability ≥ 1000) in wide combination range of film thickness for both films, although FeBN single film has high R about 400 μΩcm, B_s about 12 kG and semi-hard magnetic properties with perpendicular magnetic anisotropy. SEM observation suggests that soft magnetic properties of FeN/FeBN multi-layers originate in their in-plane anisotropy and fine grains in the films. Despite film thickness over 2 μm, permeability of about 1000 was maintained even near 100 MHz. Enhanced frequency response of permeability is strongly attributed to the increased electrical resistiviy of the films, multi-layered with FeBN.

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Magnetic properties and structure of FeN/AlN multilayered films deposited by r.f. magnetron sputtering were studied. H_c decreased as the ratio of a FeN layer thickness to a AIN one became small. H_c also decreased with decreasing film thickness of FeN/AIN bilayers. H_c and 4 πM_s in a 22Å/11Å multilayered film were 1 Oe and 8.5 kG, respectively. The film had high permeability, μ', which was 800 at a 5 MHz and 650 even at a 100 MHz because of high resistivity. SEM observation and μ-AES analysis revealed the film had a layered structure. X-ray diffraction made it clear that high permeability was ascribed to fine grains and smaller lattice mismatch between layers compared to the thick layered films.

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Fe multilayered films with Fe_xN intermediate layers of various structures (Fe + Fe₄N, ε + Fe₄N, ε and Fe₂N) are prepared by reactive sputtering under various nitrogen partial pressure conditions. Effects of Fe_xN intermediate layer on coercivity (H_c), saturation magnetization (B_s) and structure of Fe/Fe_xN multilayered films are investigated. Fe/Fe_xN multilayered films with intermediate layer prepared under conditions in which Fe₂N single layer is obtained have a low H_c of less than 1 Oe. In these multilayered films, we observe that columnar growth of Fe layer is interrupted, grain size decreases below 100Å and lattice spacing of α-Fe (110) plane increases. Low H_c of Fe/Fe_xN multilayered films is thought to be caused by these results.

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Fe-Zr/Fe-Zr-N multilayered films were prepared by alternation of Fe-Zr sputtering and electron cyclotron resonance (ECR) plasma nitridation, and the thermal stability of their soft magnetic properties were inverstigated. Saturation flux density B_s = 1.8 T, coercivity H_c = 88 A/m and relative permeability μ' > 3000 (at 20 MHz) were respectively obtained on Fe₉₂Zr₈/Fe₉₂Zr₈-N multilayered film after annealing at 773 K for 3600 s. Addition of Zr for Fe/Fe-N multilayered films improved effectively the thermai stability of soft magnetic properties.

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