Tatsuaki Ishida

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.

A novel magnetic printing technique for perpendicular recording media

A novel magnetic printing technique designed for perpendicular hard-disk media using a lithographically formed master disk was satisfactorily demonstrated. In this paper, optimum conditions for the magnetic printing process are discussed by analyzing the waveforms of signals experimentally retrieved from the printed media and by numerical simulation using a finite element method.

Magnetic printing technology - application to HDD

As the recording density of hard disk drives is being rapidly increased, the current servo track writing method using a conventional servo track writer has become more costly and technically difficult. In order to solve the problem, the authors propose a new magnetic contact duplication technology using a lithographically patterned master disk and discuss the printing process reliability for practical implementation to the product drives, in particular, from the viewpoint of master-slave contact issues. The air channel structure provided on the master disk surface allows close surface contact between the master and the slave disks, yielding very small amplitude modulation of the printed signal. The master disk was found durable over 1 million printing shots without giving any serious damage to the lithographically patterned ferromagnetic film. Moreover, organic and inorganic contamination tests show that the contact printing operation does not increase contamination on the printed disks. The magnetic printing technique can also be successfully applied to perpendicular recording media using the same master disk as for longitudinal media.

Demodulation of servo tracking signals printed with a lithographically patterned master disk

Demodulation of the servo tracking signals magnetically printed on hard disks by using a lithographically patterned master disk has been studied. Position signal decoded from the printed servo pattern was successfully demonstrated on a spin stand. Position error evaluated in a prototype drive was 30% track pitch. Pulse timing shift control by compensating the pattern dimension, and introduction of a more sophisticated servo control system for actively controlling the printed pattern eccentricity would be key issues for further improvements.

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.

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.

A novel magnetic printing technique for perpendicular media

Summary form only given. A magnetic printing technique for longitudinal media using a lithographically formed master disk has been proposed and satisfactorily demonstrated (W. Bernard and W. Buslik, 1975; T. Ishida et al., 2001; A. Saito et al., 2001). However, promising printing techniques for perpendicular media have not yet been proposed. We report a satisfactory implementation of a novel magnetic printing technique designed for perpendicular media.

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.

In-Plane Anisotropy and Recording Characteristics of Vacuum Deposited Co-Cr Films

In fabricating Co-Cr films using a continuous vacuum deposition system, the angle at which the vapor beam is incident on the substrate affects the magnetic properties and recording characteristics of the resulting film. Co-Cr films deposited at incident angles from 55° to 20° and from 70° to 20° are anisotropic, while films deposited at incident angles from 20° to ¿20° are isotropic in the film plane. The azimuth angle dependence of the reproduced output in these films correlates fairly well with the angular dependence of Mr in the film plane. The isolated playback wave-form from films deposited with the angle of incidence ranging from 55° to 20° has a MMF dependence in the normal head scanning direction, whereas that of films deposited from 70° to 20° is independent of the MMF in both the normal and the reverse head scanning directions.

Co-Cr Thin Films Deposited on Substrates with Island Structure

The effect of substrate morphology on the perpendicular anisotropy of Co-Cr films was studied. Co-Cr layers were deposited on top of Al-3 wt% Cu underlayers; the latter were of thickness 1.5 to 40 nm and were deposited at a substrate temperature of from 25 to 300°C. SEM photographs revealed an island structure for the Al-Cu films deposited at 300°C, while those deposited at 25°C had a flat surface. The ¿ ¿50 and Hkeff of Co-Cr films on Al-Cu underlayers deposited at 300°C were about 15° and 2 kOe respectively, while the figures when the Al-Cu layer was deposited at 25°C were under 10° and about 3 kOe respectively. The morphology of the Al-Cu underlayer thus greatly influenced the perpendicular anisotropy of the Co-Cr film.