Carbon film sputtered in hydrocarbon atmosphere for overcoat of thin film disk was studied. Hardness of the film and hydrogen content in the films were measured. Hardness of the films decreased with increasing hydrogen pressure in sputtering. A lot of hydrogen atom were detected in the films. Ramman spectroscopy investigation clarified that the film has almost same spectrum to i-carbon. On CSS test, friction coefficient value of hydrogenated carbon films with liquid lubricant is lower than the value of standard sputtered carbon. However ordinary sputtered carbon films without lubricant show better CSS characteristics than i-carbon. So, it seems that carbon with hydrogen films may have rather strong adhesive force to lubricant.

抄録全体を表示

  A satisfactory theory must account quantitatively both for the Kerr magneto-optical loop displacement and the anomalous torque segments observed in exchange-coupled ferrimagnetic bilayer films. The bilayer free magnetic energy density, E(α), must be even [E(α) = E(-α)] in angular dependence and in the form of an inverted parabola near α = 0 (H perpendicular to the plane). The thin wall model satisfies symmetry; however versions of the distributed wall model do so only partially. The anomalous torque behavior cannot be properly predicted from any of the theories employed.

抄録全体を表示

  Thermal stability of Fe-Zr sputtered films were evaluated for various annealing process in order to determine the reliability of recording media and to investigate the origin of perpendicular magnetic anisotropy. Films with Zr content of about 10 at.% at annealing temperature T_A below 300°C did not exhibit any degradation of the perpendicular magnetic anisotropy Ku. Ku degraded at T_A above 400°C. Saturation magnetization increased with increase of T_A in the range above 300°C, because of the recrystallization of Fe grains in the films. Fe-Zr sputtered films with proper K_u possessed sufficient thermal stability at temperature below 200°C.

抄録全体を表示

  Magnetic properties, microstructure and overwrite characteristics of Co-Pt sputtered media were examined. Large in-plane coercive forces were made for films with both large and small magnetization Ms. In case of longitudinal magnetic anisotropy, in-plane coercive force Hc increased and coercive squareness S* decreased with perpendicular magnetic anisotropy Kp increasing for large Ms films. Hc was larger and S was smaller for small Ms, films than that of large Ms films. TEM image indicate that the grains of small Ms films were isolated. Remanent coercive force dependence for large Ms films on the direction of the applied magnetic fields suggest the domain wall reversal mechanism. It was found that OWM related to the remanent coercive force along the oblique direction.

抄録全体を表示

  Light rare earth (LRe) alloys have been studied for perpendicular magnetization recording (PMR) new film media in this paper. Concerning the possibility of uniaxial perpendicular magnetization film (PMF) could be realized for crystalline Nd_x Fe_1-x, various x and substrate temperature T_s have been attempted, for x within 50-60 at%. and T_s of 200-250°C, crystalline NdFe PMF with typical uniaxial anisotropy have been obtained. NdFeB films have also been studied. Results showing that in certain composition ratio range and T_s around 250°C, crystalline NdFeB PMF will possible to be realized. The coercivity of the perpendicular magnetization film can also be lowered to a level around 79.6 kA/m (1.0 kOe). All this showing that LRe alloy films might be prospective for PMR application.

抄録全体を表示

  Co/Cr multilayered films deposited on glass substrates by rf magnetron sputtering have been annealed in 300°C and 500°C in vacuum. The intensities of satellite peaks decrease and disappear with annealing. In correspondence with the decrease in the satellite peak intensity, the magnetization per Co volume, M_Co, decreases with annealing. We have calculated the time dependence of the decrease in M_Co by assuming the interdiffusion of Co and Cr at the layer boundaries, and have estimated the coefficients of the interdiffusion of Co and Cr. The activation energy for the diffusion is estimated as 0.2∼0.5 eV, and this value suggests that the diffusion occurs due to the grain boundary diffusion. The RBS profiles of the Co/Cr double layers have been investigated after annealed at 500°C and they indicate that Cr is faster to diffuse into Co layer than Co into Cr layer.

抄録全体を表示

  High density recording required magnetic recording media with high coercivity and low noise. This paper reports CoCrTa sputtered thin film disk media developed by sputtering conditions to meet these requirements. Coercivity of 2450 Oe can be obtained CoCrTa on Cr underlayer with high substrate bias voltage. Microstructure observation by TEM and electron diffraction analysis revealed that high coercivity film has higher orientation of c-axis in the plane.

抄録全体を表示

  Both FeNi and CoCr/FeNi films were prepared by a DC planar magnetron sputtering system. This paper describes the effects of sputtering conditions of FeNi films on the magnetic characteristics and structure of FeNi films and CoCr/FeNi films. It was found that the FeNi film is sensitive to the deposition conditions, the sputtering parameters have great influences on the (111) preferred orientation and the magnetic properties of the FCC FeNi films, satisfactory soft magnetic properties of FeNi films can be obtained by decreasing the argon pressure and the film thickness and/or raising the substrate temperature. The degree of C-axis preferred orientation of CoCr films deposited onto the FeNi films is strongly dependent on the degree of (111) plane orientation of FeNi films, this may be the result of the epitaxial growth of CoCr film with its (0002) plane parallel to the (111) plane of FeNi film. Some experimental results show the magnetic properties of CoCr/FeNi double layers is related to that of the FeNi film. It is pointed out that a FeNi underlayer with satisfactory properties is the prerequisite condition for obtaining CoCr /FeNi double layers with desired properties.

抄録全体を表示

  Multilayered thin Cr/CoNi/Cr films with Hc values of up 2260 Oe are deposited on glass by ion-beam source. The correlation between Hc values and film structures is established. The key factor for Hc increasing is determined to be preferred orientation of HCP CoNi(110)/Cr(200) films. Maximum Hc value is obtained when there is some small amount of disoriented HCP CoNi phase in above preferred oriented films. This fact corresponds to hexagonal triplet presence in X-ray diffraction spectra, which can be discovered by sensitive analisis methods only. The conditions for Hc mean values of up 2000 Oe achievement are determined. Hc values increase as the amount of texture HCP CoNi(101) is increased when Cr (200) texture is absent. In this case mean Hc values is about 410 Oe.

抄録全体を表示

  The magnetic and microstructual properties of CoPdCr ternary alloy thin films were studied as a function of Pd and Cr contents from 0 to 30 at%. The CoPdCr alloy films were prepared on glass substrates at room temperature by co-sputtering of CoPd and Cr targets. The alloy films show the perpendicular magnetic anisotropy in the vicinity of 20 at% Pd and 10 at% Cr. The magnetic properties of typical composition, (Co₈₀Pd₂₀)₈₆Cr₁₄, are as follows: Ms=615 emu/cc, Hkeff=3.4 kOe, HC(⊥)=610 Oe. As the content of Pd increased, the measured lattice constants of hcp structure became larger and enhancement of c-axis perpendicular orientation was induced. It is indicated that this microstructural change caused the increase of perpendicular anisotropy field(Hkeff), and that Cr addition contributes to increase the perpendicular coercivity.

抄録全体を表示

  In this study, the dependence of crystal structure on substrate temperature T_s and the effect of additional elements such as Ta, Ge, Si and Co in the Cr underlayer of CoCrTa/Cr-M bilayered films have been investigated. Specimen films were prepared at the Argon gas pressure P_Ar as low as 0.1 to 2 mTorr by using Facing Targets Sputtering(FTS) apparatus. The amount of additional elements in Cr underlayer were controlled by constructing the composited targets. Cr-Ta and Cr-Ge films exhibited orientation of bcc(110) phase of Cr(Cr_bcc(110) phase) only, however Cr-Co and Cr-Si films showed both Cr_bcc(110) and Cr_bcc(200) phase. CoCrTa/Cr-Ta films had almost constant coercivity H_c of 500 Oe and Hc of CoCrTa/Cr-Co films increased with increase of T_s and reached about 1000 Oe at T_s of 300°C.

抄録全体を表示

  Co₈₁Cr₁₉/Al multilayered films with thicknesses of Co₈₁Cr₁₉layers in the range of 46∼170 Å and Al ones in the range of 7 Å∼14 Å have been prepared on glass-slide substrate at room temperature by using the facing targets sputtering (FTS) apparatus. The dependence of the magnetic and crystallographic characteristics on the thicknesses of Co-Cr layers and Al ones have been investigated. The magnetoresistance effect of the specimen films have been also examined. The intrinsic Co₈₁Cr₁₉ layers were composed of hcp phase crystallites with well orientation of the c-axis normal to the film plane. Both the crystallinity of Co₈₁Cr₁₉ layers was improved and the d-spacing between the c-planes was expanded by using the Al interlayers. The saturation magnetization, the coercivity, and the in-plane squareness ratio depended strongly on the thicknesses of Co₈₁Cr₁₉ layers and Al ones. The magnetic anisotropy can be controlled by the thickness of Al layer. The magnetoresistivity ratio was negative and its absolute value was as small as 0.05% in 14Å-Al layer.

抄録全体を表示

  The 100Å-thick Co₇₉Cr₂₁ underlayer was helpful not only for improving the crystallinity of Ni-Fe backlayer deposited on the underlayer, but also the c-axis orientation of Co₈₃Cr₁₇ recording layer on the backlayer through an hetero-epitaxial growth between fcc-(111) of Ni-Fe crystallites and hcp-(002) of Co-Cr ones. Electron beam diffractometry and TEM observation for them indicated that Co-Cr ultra thin layer with higher Cr content is suitable as a seed layer to improve crystallinity of upper layers, such as Co-Cr layer and Ni-Fe layers deposited on it. The Co₇₉Cr₂₁ ultra thin layers were used as the interlayer between Co₈₃Cr₁₇ recording layer and Ni₈₁Fe₁₉ backlayer to improve the crystallinity and magnetic properties of these media.

抄録全体を表示

  A rheomagnetic measurement (RM) device which is suitable for online characterization of both the concentration and dispersion quality of magnetic suspensions during the early stages of slurry production is presented. New results on the measurement and interpretation of the RM data for the plate-like particles used in perpendicular recording are presented. The results reported are markedly in contrast to those previously obtained for the rod-like particles used in longitudinal recording.

抄録全体を表示

  BaFe_12-2xCo_xTi_x-ySn_yO₁₉ powders with x = 0 - 0.9 and y = 0 - 0.4 have been prepared by the glass crystallization method. The individual single crystalline and single domain particles possess a perfect M-type structure and a narrow log-normal grain distribution. The mean particle diameters for x ≈ 0.8 and y = 0 - 0.4 are between 40 and 80 nm and the mean aspect ratios between 3 and 6; the diameters can be varied in between 10 nm and 1μm. Magnetization data are diminished by an effective nonmagnetic layer (about 1nm thick) parallel to the basal surface of the hexagonal platelets. The coercivity is decreased by substitutions of Co-Ti, Co-Si, Co-Ge, Co-Sn, and Co-Zr. Coercivity and its temperature dependence is studied in detail for the system BaFe_10.4(Co,Zn)_0.8(Ti,Sn)_0.8O₁₉. The magnetic interaction effects between the individual particles are comprehensively discussed.

抄録全体を表示

  We have succeeded in the industrial production of acicular Ba ferrite particles with a range of coercivity values (Hc) and high saturation magnetization values (σs), using the topotactic reaction between acicular FeOOH particles and fine BaCO₃ particles. Appropriate baking temperatures and baking times were an important factor in obtaining acicular Ba ferrite particles with a high saturation magnetization value while preventing fusion between these particles. Through SEM and TEM observations of magnetically oriented sheets obtained through trial manufacture, it was verified that the axis of easy magnetization of acicular Ba ferrite particles is perpendicular to the acicular direction. Also, torque curve measurements were used to verify that the magnetically oriented sheets had uniaxial anisotropy. The results show that these properties are suitable for perpendicular magnetic recording media.

抄録全体を表示

  In order to obtain Ba ferrite particles with improved characteristics for use in magnetic recording, a Co-Zn-Nb substitution system has been studied. The saturation magnetization increases with Zn substitution and shows a maximum. In this Co-Zn-Nb system, a high saturation magnetization is obtained, which is about 10% higher than that for Co-Ti substituted particles. In this case, the temperature coefficient of coercivity at around room temperature, dHc/dT, is about the same as that for Co-Ti substituted particles. On the other hand, with small Co substitution amount and large Zn substitution amount in this Co-Zn-Nb system, dHc/dT can be reduced to zero in the coercivity range applicable in magnetic recording.

抄録全体を表示

  In order to obtain the substituted barium ferrite powder with improved characteristics for magnetic recording, the morphology, structure and magnetic properties of doped barium ferrite BaFe_12-2xCo_xSn_xO₁₉ with x = 0-1.4 have been studied. The composition dependence of magnetic properies were measured and discussed. By the law of approch to saturation it was estimated the effective anisotropy field H_A and the effective crystalline anisotropy constant K₁ for Co-Sn substituted barium ferrite particles. It was found that BaFe_12-2xCo_xSn_xO₁₉ particles with Co-Sn substitution x = 1.10-1.40 have very low temperature coefficient of coercivity ΔH/ΔT = +0.40--0.40[Oe/°C] at temperature range from 0°C to 60°C and suitable magnetic characteristics for magnetic recording.

抄録全体を表示

  Anisotropy field distribution (AFD) of randomly oriented particles was measured using VSM. AFD of two kinds of iron acicular particles were measured and the results were compared with the shape distributions of particles obtained by TEM observation. AFD of particles was closely related to the shape distribution of particles.

抄録全体を表示

  Magnetic aftereffect constant, Sv, and rotational hysteresis integral, R_h, of CO-γ-Fe₂O₃ particles, whose particle mean volume, V, is especially fine, and of VHS tapes produced on a trial basis using these particles were measured for a comparative study with those of metal and Ba-ferrite. The activation volume, v, calculated from Sv and Hc had a relationship of Hc ∼v^-0.67. V/v was approximately 4. The results were nearly the same as those with metal particles. CO-γ-Fe₂O₃ and metal particles showed the trends by which the more v and V/v decreased, the closer the coherent rotation mode became. In the case of Ba-ferrite, as Hc increases R_h decreases, to gradually approach the coherent rotation mode. The mechanism of magnetization reversal have a close relationship with v and V.

抄録全体を表示

  The effect of Mo content on microstructure of CoCrMo thin films was investigated and its dependence of perpendicular coercivity. The microstructural investigation illustrated that grain size and columnar structure are dependent upon Mo content. Mo addition improved c-axis perpendicularity of hcp phase and prohibited Cr segregation in the CoCr films containing Mo. Perpendicular coercivity of films was dependent upon grain size and columnar structure rather than c-axis orientation.

抄録全体を表示

  Magnetic anisotropy and magnetization measurements have been made on a series of Ni-Zn ferrite thin mms prepared using a new low temperature (T < 100 C ) ferrite plating technique developed by one of the authors. Films made by this technique are of considerable interest because of their potential use in the fabrication of microwave non-reciprocal components (e.g. circulators) on GaAs monolithic integrated circuits. In order to successfully employ the ferrite films in such applications it is important to characterize and understand the magnetic properties of the films. In this paper we show that the perpendicular magnetic anisotropy depends strongly on the Fe²⁺ ion concentration and can be explained in terms of a single ion anisotropy directed along a [111] texture axis perpendicular to the film plane.

抄録全体を表示

  Realization of excellent head-to-tape interface is important to achieve high recording density in VCRs. Especially, anisotropy of mechanical characteristics of tape influences head-to-tape contact. In the present study we have measured anisotropy of Young's modulus of magnetic tapes by measuring the ultrasonic propagation velocity. The anisotropy of particulate medium differed from that of evaporated medium. We have made computational calculation by FEM (Finite Element Method) of the deformation of tapes having anisotropy of mechanical characters and sliding over head fixed on a rotating drum. The flexible tape is modeled as a thin anisotropic shell and the air-film is treated by the modified Reynolds equation. Good agreement between calculation and measurement has been obtained.

抄録全体を表示

  To improve cleanability of the liner for the flexible disk, we attempted to extend mechanism of catching dust from simple physical catching of conventional liners to catching by adhesion(chemical force). As a result, it was proved that we could get the mechanism of catching dust by adhesion due to processing of the liner with appropriate silicone oils. This liner showed much better cleanability than conventional liners to dust particles of about 20 μm which would possibly cause dropout in flexible disk with higher density than 3.5" 2ED(unformatted capacity of 4MB).

抄録全体を表示

  We have studied two types of head supporting mechanisms for a non-flying single-pole-type head (SPT head). One is a self-weight type, in which the smooth up-and-down motion of a head is achieved using a micro linear bearing. The other is a balanced type that achieves the access to both sides of the disks and make the disk access stable under acceleration over 1 G. Both new supporting mechanisms show a good off-track and a track access characteristics. After the seeking of 7 mm distance on a disk, a reproduced voltage fluctuation with the new type mechanism is less than 2 % that corresponds to the off-track distance of 2 μm, whereas, that with the conventional type mechanism is 5 %-10 % that corresponds to the off-track over 10 μm. A head installed in this head supporting mechanisms follows the disk up to 3600 r.p.m.. This result agrees well with the calculated results of the head motion using the equation of motion.

抄録全体を表示

  Head-media interface of CoCr and metal particle stretched recording disks is investigated using a slotted spherical slider. Acoustic emission output of the stretched disk scarcely depends on the flying height. Frictional coefficient in high speed region of the stretched disks is higher than that of a rigid disk which is almost zero. In contrast the coefficient in low speed region are lower than that of the rigid disk. These peculiar running behavior must be based on elasticity of the stretched medium. The change of spacing is less than 0.1μm below 6m/sec of running speed. Using the slotted spherical slider with the optimal radius of curvature even the CoCr stretched disk shows the durability over 100 million passes. These results suggest the possibility of a high density recording disk system based on such "quasi-contact head-media interface".

抄録全体を表示

  A simple thin film head which we call "Mellisuga Head" has been developed. The head has an extremely low flying height, which can be adjusted between 0.03 μm and 0.07 μm at 11.3 m/s of head/disk relative velocity by modifying the gross ABS area and a gram load. Significant improvement of electrical performance was attained primarily due to the extremely low flying height. Then, the reliability in the contact start stop (CSS) process and the soft dynamic load/unload (SDL) process of the head on two types of thin film disk was investigated. In the Mellisuga Head operation on a γ-Fe₂O₃ disk with a glass substrate, 50,000 CSS cycles as well as 100,000 SDL cycles were completed successfully. This confirms that the γ-Fe₂O₃ disk has an especial advantage to the Mellisuga Head operation. It was also shown that the head could be operated on a metal disk with a glass substrate during the SDL process.

抄録全体を表示

  Numerical results of dynamic response of the magnetic head slider in ultra-thin gas film considering head disk impact / contact are presented. Solutions are based on a factored implicit finite difference algorithm for the first modified. Reynolds lubrication equations coupled with a repeated fourth-order Runge-Kutta scheme for the slider equilibrium equations and with Guass elimination algorithm for the head-disk collision equations. The collisions between the head and the disk are analyzed by a "coefficient-of-restitution" model. The gas flow influence created by the asperity has been considered. The simulation results show that the collision between head and disk maybe result in failure of magnetic recording medium when there is a very high and sharp asperity on the disk surface.

抄録全体を表示

  Investigation of the molecular-level structure of the novel lubricant layers we have developed for application to thin film rigid disk systems was carried out using FT-IR reflection absorption spectroscopy. A layer of a carboxylic amine salt lubricant prepared by spontaneous adsorption, which gave the lowest friction coefficient in Contact-Start-Stop tests, was found to be a monolayer where the molecules are as highly ordered and closely packed as in a Langmuir-Blodgett monolayer.

抄録全体を表示

  In this paper we have attempted to clarify the effect of the kinetic energy of the sputtered particles on the formation of diamond-like carbon thin films using a Facing Target Sputtering System(FTS) which allows deposition of films at a very low gas pressure such as 0.2mTorr. Glass-like carbon is a kind of amorphous carbon which has very small crystallites and its structure is very uniform compare to graphite. Therefore, we have also tried to evaluate the potential of glass-like carbon as sputtering targets. The optical properties of the carbon films were measured with an optical ellipsometer. The structure of the carbon films were evaluated from Raman spectroscopy. The electrical resistivity was measured using a four point probe technique. The mechanical properties were measured with a microscratch tester. The above experimental results indicate that the structure of FTS deposited carbon films changes from less amorphous to diamond-like as the argon gas pressure is decreased and their adhesion and uniformity was significantly improved. FTS carbon films about 300Å thick were also deposited on textured Co-Cr-Ta/Cr/Ni-P/Al 3.5"rigid disks for the characterization as wear resistant overcoats. The friction of the carbon films were measured using a computer-controlled constant linear velocity drag tester with a thin film head slider. The results show that the friction coefficient decreased from 0.95 to 0.45 as the argon gas pressure was decreased from 10mTorr to 0.2mTorr. Carbon films deposited at 0.2mTorr Ar pressure show significantly lower friction and much greater durability than those deposited at 10mTorr Ar pressure. These results support the conclusion that FTS deposited carbon films have excellent potential as high-durability overcoats.

抄録全体を表示

  The plasma polymerized protective film we developed for thin film disks deposited using plasma-assisted chemical vapor deposition with diphenylethane as a monomer. The film consists of sp² and sp³ bond and has 27-36% hydrogen. It has a high ability to bond the lubricant and shows a higher durability than sputtered carbon film

抄録全体を表示

  Thin carbon overcoats were deposited on rigid disks of magnetic thin film media by RF diode sputtering using a mixture of argon and nitrogen gas. Constant drag test of thin film head sliders were performed by a computer-controlled friction-wear tester. As the nitrogen partial pressure was increased from 0 mTorr to 7.5 mTorr, the number of revolutions before wear failure increased from 3000 to 9000 revolution, the catastrophic wear was also found on carbon overcoats deposited on pure argon. The stress distribution on multilayer were also analyzed by Finite Element Method.

抄録全体を表示

  The electrodeposition process, chemical composition, structure and physical-mechanical properties of soft magnetic amorphous Co-P composite films have been studied. Fine-grained Al₂O₃ (300 nm in diameter) and submicronic-size diamond particles (100 Å) were codeposited. The incorporation of the particles has been found to increase the wear resistance of amorphous Co-P by a factor of 4-5 with, practically, no change of the main magnetic properties. The films with Hc=10-15 A/m, μ=3000, Bs=0.9 T have been obtained.

抄録全体を表示

  The tribological properties of surface-oxidized Co-Cr films were investigated. In the durability test using steel-ball sliders, sliders were severely worn out by the presence of very thin PFPE (perfluoropolyether) lubricant layers. Such anomalous wear was suppressed using a low viscosity liquid or a solid lubricant. However, low viscosity PFPE was generally ineffective to protect recording layer mechanically. Lithium stearate, a solid one, exhibited excellent lubrication performance (low friction and low slider wear) by improving the wettability of Co-Cr surfaces.

抄録全体を表示

  For high density recording, it is very important to reduce the spacing between the magnetic head and the disc, avoiding the higher risk of the head stiction and crash with the reduced spacing. This report summarizes the new DOUBLE CTX (Chemical Texturing) system for low temperature magnetic layer production. The DOUBLE CTX was found to provide excellent texture for sputtered Co-Pt of 1400 Oe at 50°C, due to no projection of the head hit at a flying height of 0.1μm and 30000 CSS materialized with no increase in friction coefficient. The magnetic measurement showed that Hc increased with the increasing depth of texturing (etching depth). Although the chemical texturing was isotropic on the disc surface, output modulation caused by the inline sputtering was not observed. It is confirmed that the chemical texturing is effective in achieving reliable sputtered rigid discs with low flyability and excellent recording characteristics.

抄録全体を表示

  This paper describes the relation between pass wear durability and medium tribological factors, including surface roughness, mechanical and chemical properties of CoCr and overcoat layers, lubrication and medium flexural rigidity. CoCr and overcoat layers were sputter deposited on various base films. Pass wear durability was evaluated by using a single-sided 3.5" flexible disk drive. CoCr wear strongly depends on the surface roughness and mechanical strength. The wear resistance is proportional to the tensile strength of the CoCr films, in accord with Archard's adhesive wear theory. The pass wear durability is improved by surface treatments, including lubrication and overcoat application. A surface active agent is effective to increase the pass wear durability, because lubricant affinity to the overcoat surface is improved. Furthermore, pass wear durability is strongly influenced by medium flexural rigidity. By optimizing these tribological factors, sufficient pass wear durability for practical use (more than 10 million passes) can be obtained.

抄録全体を表示

  A possibility of contact recording with metallic thin film magnetic disks at full speed rotation has been indicated using a plastic substrate and a modified monolithic ferrite head. Because the head loading force indents the disk surface slightly, the head always slides over the disk surface, which minimizes the head to disk separation. As a result extremely improved record and reproduce properties were achieved. Durability performance was also confirmed to a certain extent. This indicates that the storage capacity more than several hundred megabytes per 3.5" disk can be easily obtained with a disk and head combination of average magnetic properties.

抄録全体を表示

  A cause of damage to Co-Cr stretched-disk was studied. The damage to Co-Cr stretched disk was depend on the size of extraordinary asperities. Large extraordinary asperities on the medium surface caused the damage to the medium when the head hit them. If the extraordinary asperities were small, they did not cause damage, but wear debris produced by the sliding of the head over the medium caused damage to the medium. The damage to Co-Cr stretched disk was depended on a quantity of wear debris which was depended on the property of the carbon overcoat. It was found that a worn resistant carbon is effective to reduce the wear debris. The property of the carbon overcoat could be controlled by the sputtering condition.

抄録全体を表示

  The decreasing of flying hight between the slider and the disk is one of the most important items in promoting the further increase of the recording density. In order to develop a new material for the slider that is able to meet such a requirement, we have examined the CSS test and the DRAG test for various kinds of slider materials. An evaluation of slider materials based on the results of these two tests was made and the results were compared with the properties of each ceramic slider materials. These test results would show a good correlation with the micro-tribological phenomena between the slider and the disk. As a supplemental test, the contact angles of ultra-pure water dropped on the polished slider substrate were measured.

抄録全体を表示

  The Hi-Vision signals have more than 5 times the amount of information compared to the conventional television signals. Therefore, it is indispensable to attain high recording density for Hi-Vision VTRs. This paper describes the state-of-the-art of Hi-Vision VTRs and of researches on high density recording technology for Hi-Vision systems. Furthermore, the requirements for perpendicular magnetic recording are discussed, from the viewpoint of Hi-Vision recorders.

抄録全体を表示

  The application of signal processing technologies is tutorially discussed for coping with the strong demand of a higher packing density in the magnetic, optical, and magneto-optical recording systems. Firstly, the source coding and error protection scheme in the conventional transmission systems are briefly considered from the standpoint of recording systems. Finding a suitable recording code in combination with equalization and detection methods is crucially important for improving the net packing density while maintaining satisfactory data reliability. Then consideration of recording code, read process and equalization methods is given. Finally, the problem of a decoding method, especially Viterbi algorithm, and error probability are briefly investigated.

抄録全体を表示

  Co-Cr layers and metal evaporated tape with a tilted easy magnetisation direction have been investigated. In these media the recording direction with respect to the easy magnetisation direction is important. This is investigated with the help of recording experiments and recording simulation experiments. For the investigated media the same two phenomena affect the recording performance: the occurrence of interference minima in the frequency response and the steepness of the transitions. The optimum recording direction depends on which phenomenon dominates. For media with a more perpendicular easy magnetisation direction the occurrence of the minima is most important, while for the more longitudinal media the steepness of the transitions is most important. Therefore, the optimum recording direction is opposite for the two types of media.

抄録全体を表示

  Recording mechanisms and characteristics have been investigated by computer simulation on an obliquely oriented medium whose easy magnetization direction is in the neither perpendicular nor longitudinal direction. It has been shown that the magnetization direction in the inside of the medium is fixed by the leading head field but the magnetization transition is formed around the trailing edge. The demagnetizing field in the obliquely oriented medium is weak not only at a low density but also at a high density, because the anti-parallel magnetization mode is formed. Besides, the distribution of the oblique component of a ring head field is sharper than those of the longitudinal and perpendicular components. Therefore the much better recording performances are obtained comparison with longitudinal magnetic recording.

抄録全体を表示

  In preparing Ba-ferrite tapes with perpendicular, longitudinal or random orientation from the same magnetic paint, this paper investigates experimentally how the magnetic properties for the tapes, especially the orientation, the resultant switching field distribution(SFD), and a perpendicular-to-longitudinal coercivity ratio, affect their recording performance characteristics at high densities. The appropriate applications for Ba-ferrite tapes, depending on their orientation, are also discussed, referring to perpendicularly oriented tapes used for DAT magnetic contact duplication, and longitudinally oriented tapes for an 8mm VCR and a DAT.

抄録全体を表示

  In order to record two different signals on the same area of tape, overwrite recording is applied in video tape recording, but the principle is not clear. Two different orientation tapes (one is perpendicular and the other is longitudinal orientation) are used for overwrite recording, changing the signal frequency and the azimuth angle between two signals. Perpendicular orientation tape is also useful for short wavelength recording and overwrite recording, but not useful for overwrite erasing. The azimuth angle is influenced only for playback as azimuth loss and not for recording process as far as 0∼+14 degree.

抄録全体を表示

  Perpendicular orientation effects on overwrite characteristics in Ba-ferrite floppy disks (FDs) were investigated with three different heads (MTE, FTE and DS-MIG heads). The principal results are as follows. (1) The relationship between overwrite modulation and overwritten signal density depends both on head type and media orientation. (2) The effect of overwrite on bit shift cannot be judged by the OWM value for a particular density. (3) For both a 20kFRPI and a 35kFRPI signals overwritten on pre-recorded random pattern signal, in the 1-7 coding system, the total bit shift for Ba-ferrite FD is smaller than that for metal FD.

抄録全体を表示

  An experimental high-speed magnetic recording channel using a new metal alloy composite head with 150 MHz bandwidth capability and metal particle tape has been constructed. At the linear density of 4 kfr/mm (95 to 100 kfr/in) and Nyquist frequency of 150 MHz, the measured 300 kHz slot SNR was greater than 32 dB. Using a DC-free 11-12 code at a data rate of 250 Mbit/s and density of 3.35 kfr/mm (85 kfr/in), error rates of 1x10^-5 were measured. Under these conditions, a 300 kHz slot SNR of 37.5 dB at 125 MHz was measured.

抄録全体を表示

  Based on the 4MB 3.5" Perpendicular Recording/Longitudinal Recording Floppy Disk Drive with a track density of 270 TPI, we further developed a 3.5" Perpendicular Recording Floppy Disk Drive demonstrating the potential to realize a capacity of more than 8MB capacity. The key technology included: (1) a Perpendicular Recording/Longitudinal Recording Floppy Head which was without erase element and helped realize the capacity of 4MB-8MB under the condition of without using servo system for tracking. (2) The GAL Technology to expand the Application-Specific Integrated Circuits. (3) The improvements of the read write channel.

抄録全体を表示

  The characteristics of high density FM perpendicular magnetic recording using a Co-Cr medium and a MIG-type ring head were investigated. The Co-Cr medium showed little tendency for the lower sideband enhancement and higher sideband suppression expected with a particulate medium. Even if the carrier wavelength is 0.4 μm, the combination of the Co-Cr medium and the MIG type ring head performs well. The Co-Cr medium, however, is not suitable for dual-frequency recording because of its high level cross modulation caused by the rapid inversion of the recorded magnetization in the medium. We made a high-resolution video test recording using a 2" Co-Cr disk. Even though the wavelength at the white peak was as short as 0.3 μm, a resolution of more than 480 lines was obtained and no inversion noise was observed. We confirmed that the combination of the Co-Cr medium and the MIG-type ring head is suitable for a high density analog FM video recording system.

抄録全体を表示

  Read/Write characteristics are studied using a newly developed 1 micron trackwidth inductive-write/MR-read dual-element head and a Co-Cr-Pt/Co-Cr-Pt-Si dual-layered low noise medium. The 8/9 block coding, extended class IV partial response signalling and Viterbi detection are applied to the read/write data channel. A linear density of 120 kBPI with a bit error rate of 10^-8 is achieved from ontrack measurements at a magnetic spacing of 0.08 μm. The possibility of a 1.5 μm track pitch(16.9 kTPI) is discussed based on offtrack measurements. The present head-medium system showed a sufficient track density resolution of 16.9 kTPI.

抄録全体を表示