Nobuyuki Nagai

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.

Highly field sensitive (150 Oe) quadri-valued magnetooptical media for high-speed overwriting

For high-density and high-speed magnetooptical (MO) recording, the use of magnetic multi-valued (MMV) MO media has been proposed. [rf:1] A quadri-valued recording has been achieved using this media and a field modulation recording method. For practical use of this media, it is important to reduce the critical magnetic field to minimize the applied field for realizing the quadri-valued recording. We have achieved reduction of the critical magnetic field down to 150 Oe using a new coupled film, TbFeCo/GdTbFeCo.

Magnetic parameter control for high‐density quadrivalued MO recording (invited) (abstract)

To increase recording density of MO media, several schemes have been proposed. Among them, magnetic multivalued (MMV) recording is one of the most promising methods. We have first realized the quadrivalued MMV media using a field modulation method. Such media is composed of an exchange coupled TbFeCo/PtCo bilayer. By switching the external field in four levels, the separated signal corresponding to the each field is obtained as a four leveled output. For the acutal device application for high‐density and high‐speed recording, it is necessary to reduce the external field as small as possible. In the previous experiment, about ±900 Oe was necessary to record the whole levels. For such MMV media, the quadrivalued signal response depends on the magnetic characteristics of the TbFeCo/PtCo bilayer, which is so called dual write state. The higher field level on the MMV media is defined by the threshold field of the dual write state. It is found that the threshold field is controllable to tune the magnetic parame...

Edge Shift Of Written Domain In Magnetic Field Modulation Method For Magneto-Optical Disk

We have investigated the edge shift of written domain in magnetic field modulation recording for magneto-optical disk. The edge shift between the timing for the recording and reproducing signal edges is inevitable. We have proposed an edge shift compensation method for the purpose of applying the magnetic field modulation method to embedded clock system.