Kiyokazu Tohma

Printed Media technology for an effective and inexpensive servo track writing of HDDs

As an alternative method for the servo track writing of hard disk drives (HDDs), a magnetic contact duplication method by using a lithographically patterned master disk has been proposed and investigated. On the master disk, magnetic film pattern according to the information signal to be printed on slave disks is provided by a lithography technique. In this method, unlike the anhysteretic process of the conventional contact duplication method for magnetic tapes, the master information never disappears when a large external field is applied to the master while printing. This duplication method, as we call the Printed Media technology, can provide a very effective and inexpensive lump-sum servo track writing method for HDDs.

Incident angle dependence of recording characteristics of vacuum deposited Co-Cr films

The authors report on an investigation of the relation between the incidence angle of evaporated atoms onto a substrate and the magnetic properties, microstructure, and recording characteristics of Co-Cr films. The Co-Cr films deposited at an oblique incidence angle have an easy axis of magnetization which tilts from the film normal and consist of columnar grains which tilt from the film normal. For films deposited at an incidence angle from 55 degrees to 20 degrees , the isolated pulse waveform is not a double pulse, but a single-peak-like pulse with narrow pulse width. An eye pattern for moving-picture digital recording was clearly observed using the Co-Cr tapes. The compensation amplitude in the short wavelength region was very small, and equalization such as a Hilbert transform was unnecessary for films deposited at an incidence angle from 55 degrees to 20 degrees . >

More than 1 Gb/in/sup 2/ recording on obliquely oriented thin film tape

We discuss the possibility of attaining more than 1 Gb/in/sup 2/ recording in helical scanning tape storage system based on obliquely oriented metal evaporated tapes. A demonstration of 1 Gb/in/sup 2/ recording using an inductive MIG type head is described. Other experimental results show that the obliquely oriented Co-O tapes are endowed with recording resolution potential beyond several Gb/in/sup 2/, but playback signal-to-noise challenges still remain. Applying more sensitive magneto-resistive heads in the helical scanning tape system requires significant innovation in the system to overcome crucial issues of contact recording as well as re-optimization of the magnetic properties of the tape.

Vacuum deposition of Co-Cr perpendicular anisotropy films on polymer substrates treated with ion beam

The author investigated the effect of ion-beam treatment of polymer substrate surfaces on magnetic properties, microstructure, adhesive force, and recording performances of vacuum-deposited Co-Cr films. Films which are deposited on the ion-beam-treated substrates have higher H/sub c perpendicular to / than that of the films on untreated substrates without the treatment and have H/sub keff/ values high enough for perpendicular magnetic recording applications. With ion-beam treatment the adhesive force of the Co-Cr films is considerably improved, becoming of practical strength. The films deposited on the treated substrates reproduced voltage as high as that of Co-Cr films with Ti underlayer. Ion-beam treatment of the polymer substrates therefore makes both glow discharge treatment and the use of a Ti underlayer unnecessary and promises high manufacturing productivity. >

Effects of Incident Angle on Recording Properties of Vacuum Deposited Co-Cr Films

The recording characteristics of Co-Cr films were investigated with respect to the angle at which evaporated atoms are incident on the substrate during film deposition. The recording characteristics of Co-Cr films deposited at angles of incidence of 55° to 20° depend on the head scan direction. In the normal direction, the magnetization in the film is recorded mainly by the magnetic field near the leading edge of the head, while in the reverse direction it is written mainly by the field near the trailing edge. The single-peak-like isolated waveform in the normal head scanning direction is explained as the super-positioning of the waveform reproduced from the magnetization recorded by the head field near the leading edge, and the waveform from magnetization reversals at the film surface which are written by the field near the trailing edge. The reproduced voltage from the film medium decreases with increasing azimuth angle, owing to the magnetic anisotropy existing in the film plane, while Co-Cr films deposited at incident angles of 20° to ¿20° have almost the same density response at different azimuth angles.

Method for providing a perpendicular recording medium for use with a ring-shaped recording and reproducing head

A perpendicular magnetic recording method uses a perpendicular magnetic recording medium. This medium comprises a perpendicular anisotropy film having perpendicular remanent magnetization Mr and longitudinal remanent magnetization Mr.sub.∥, wherein the value of the ratio Mr.sub.⊥ /Mr.sub.∥ is not less than 0.2, but is less than 1.

Incident angle dependence of the magnetic properties of vacuum deposited Co-Cr films

Abstract The incident angle and the substrate temperature dependence of the magnetic properties of continuously vacuum deposited Co-Cr films was investigated. The inclination of the easy axis form the film normal toward the film plane in the incidence plane became large with increasing incident angle. The magnetic anisotropy field of the films deposited at oblique incidence decreased with increasing substrate temperature. X-ray analysis and TEM observation showed that the magnetocrystalline anisotropy was dominant at low incident angle and the shape magnetic anisotropy was dominant at high incident angle. Also investigated was the effect of an initial layer on the magnetic properties and the crystal orientation of a Co-Cr film. The easy axis of the film was titled by the Co-Cr initial layer deposited at high incident angle, because the c -axis tilted as a cinsequence of epitaxial growth on the initial layer.

Spacing Loss of Vacuum-Deposited Co-Cr Tapes

In the fabrication of Co-Cr films using a continuous vacuum-deposition system, the incident angle of the vapor beam on the substrate affects the recording characteristics of the film with respect to the spacing loss. The spacing loss factor rises with increasing film anisotropy field Hkefr when signals are recorded and reproduced with a ring head. For Co-Cr films deposited with the angle of incidence varying from 20° to ¿20° the spacing loss is large, loss factor of 140 dB, while for films deposited at incident angles varying from 55° to 20° and from 70° to 20°, the loss factors are estimated to be 110 dB and 85 dB respectively. The head-medium spacing of 40 nm is made up of protrusions and a protective layer indispensable for ensuring the durability and playability of VCR tapes. Films deposited with the incident angle varying between 55° and 20° are advantageous for high-density recording.

Improvement of Performance in Continuously Vacuum Deposited Co-Cr Film by Substrate Treatment

Dependence of the perpendicular anisotropy of continuously vacuum deposited Co-Cr films on glow discharge treatment of the polymer base film surface, and on the thickness of a Ti underlayer, was investigated. The relation between the film microstructure and the recording characteristics of the Co-Cr film media was also studied. When the polymer film surface was pretreated by glow discharge with Ar gas, the Hkeff of the Co-Cr films decreased, but when H2 gas was used instead of argon, the deterioration of the Hkeff was negligible. Co-Cr films deposited on a Ti underlayer had a high Hkeff regardless of the glow discharge treatment conditions. The Ti underlayers had to be more than 40 Å thick in order for the Co-Cr films to have a small ¿¿50, around 5 or 6°. The Co-Cr films showed a columnar structure when the Ti underlayer thickness was in the range from 100 to 2000 Å Co-Cr films with a columnar structure yielded a high reproduced voltage.

Composition control for evaporated CoCr thin films

Composition control was achieved in fabrication of CoCr thin films by evaporation onto tape-shaped polymer substrates. The vapor composition during deposition was determined by an atomic absorption type of detectors and a composition calculator. The gradual change of composition during deposition due to the difference in vapor pressure between Co and Cr was compensated by supplying Cr into the evaporator. As a result, the desirable composition was obtained to within an accuracy of 0.4 wt.%. This composition control system was shown to be suitable for the preparation of CoCr perpendicular magnetic recording media. >