Osamu Ishizaki

Direct overwriting capability of magnetic multivalued MO media

As one of the most promising schemes for high density MO recording, a new media for magnetic multivalued recording has been proposed. By switching the external field on four levels, the quadri-valued signal was obtained. On the MMV media, field sensitivity is improved by controlling composition of PtCo capping layer coupled to TbFeCo. The external filed for recording four levels is reduced down to 350 Oe and direct overwriting capability is confirmed on 0.8micrometers mark length recording.

Zero-Field Magnetic Amplifying Magnetooptical System Applied to Next Generation “iD PHOTO” System

We investigated very high-density recording performance of the zero-field magnetic amplifying magnetooptical system (MAMMOS) with a 635 nm laser diode and a 0.60 N.A. objective lens. It was shown that the linear bit length of 0.13 µm was successfully reproduced with sufficient readout margins. The recording density up to 7.1 Gbit/in2 was demonstrated by combining the zero-field (ZF)-MAMMOS with an in-groove disk structure.

Plastic substrate preembossed 100 kbpi, 3.4 μm track width magnetic disk (abstract)

To achieve higher areal recording density and at the same time very low cost magnetic media, a preembossed disk is proposed in which servo marks, header signals, and ROM data are formed on a plastic substrate by an injection method. Those media give very attractive features to reduce track pitch comparable to optical disks. A very expensive and low throughput servo writer is not necessary by using such preembossed servo marks. To realize the preembossed disk, a magnetic layer should be prepared by low‐temperature deposition. In this paper, we studied the sputtering process and suitable magnetic materials such as CoCrPt/Cr film on plastic substrate. Plastic substrate was made by amorphous polyolefin (APO). The under layer (Cr), magnetic layer (CoCrPt), protective layer (C) are formed by magnetron sputtering without substrate heating. Effects of Pt content, thicknesses of magnetic layer, and under layer were investigated. Results showed that coercivity was achieved to 1900 Oe at Pt about 20 at. %, 30‐nm‐thi...