JPS61229247A - Photomagnetic medium - Google Patents

Abstract

PURPOSE:To record a high-frequency signal and to perform overlapped write by providing in advance a track generating an external magnetic field of different magnetizing directions to both sides of the recording track. CONSTITUTION:The external magnetic field generation tracks 7, 8, 9 on which vertical magnetic fields of different directions is recorded in advance are provided to both sides of the recording track. It is possible to record a binary signal on the recording track by irradiating selectively an elliptic spot irradiated on the external magnetic field generation tracks 7, 8 provided at both sides of the recording track 5. That is, the irradiation of two laser beams is controlled to control the direction of a floating magnetic field at high speed and high speed magnetic field modulation is applied, then overlapped write of the high frequency signal is applied to the optomagnetic medium.

Description

[Detailed Description of the Invention] (Background of the Invention) Optical modulation methods and magnetic modulation methods are known for writing signals on magneto-optical media, and the former method is used to record high-frequency signals of data (high-speed data rate). However, since overwriting is not possible, it takes time to switch between writing and erasing, and erasing a recorded medium requires the same amount of time as the writing time, so it takes time.

On the other hand, the latter allows overwriting, but the perpendicular magnetization film and the electromagnetic coil are structurally separated by more than 2III11, so in order to obtain the magnetic field required by the medium, the number of turns of the electromagnetic coil must be increased or a large current must be passed. , this degrades the transient response,
This increases the time required to obtain a predetermined magnetic field, lowers the upper limit of the recording frequency, and increases the size of the device.

(Objective of the Invention) An object of the present invention is to solve these drawbacks and to make it possible to record high-frequency signals on a magneto-optical medium and to enable overwriting.

(Summary of the Invention) The present invention provides external magnetic field generating tracks with different magnetization directions on both sides of a recording track of a magneto-optical medium, and when recording, the magnetic field of either of the external magnetic field generating tracks is applied. The technical point is to use it selectively.

(Embodiment) FIG. 1 shows an embodiment of the present invention, and (a) is a partial plan view of a grooved disk-shaped magneto-optical disk (hereinafter simply referred to as magneto-optical disk) having concentric recording tracks. , (b) are partial cross-sectional views of the magneto-optical disk according to the present invention, which are cross-sectional views taken along the line A--A in FIG.

In FIGS. 1(a) and (b), 1, 2.3 are spots irradiated with the laser output onto the recording surface of the magneto-optical medium, 1 is a circular laser spot, 2.3 is an elliptical laser spot, These are obtained by three semiconductor lasers and one objective lens. Reference numeral 4 denotes a disk substrate in which concentric grooves for setting concentric recording tracks are provided in advance, and is manufactured by injection, casting, or the like.

Perpendicular magnetization films 5 to 9 made of TbFe or the like having high saturation magnetization are formed on the surface of the disk substrate 4 on which the grooves are provided.

The perpendicular magnetization film 5.6 is a recording track, ? , 8.9 is a track for generating an external magnetic field, and the track for generating an external magnetic field? , 8
．． 9.・−・−−−1−− is magnetized in advance prior to signal recording so that the magnetization direction is sequentially reversed.

In FIG. 1, the track 7.9 for generating an external magnetic field is directed upward, and
is magnetized downward.

In pre-magnetization, which is carried out in advance before signal recording, the entire magneto-optical medium is first placed in a strong upward external magnetic field to magnetize all the perpendicularly magnetized films 5 to 9 upward.

Next, every other external magnetic field generation track is magnetized downward using a weak downward external magnetic field and a laser spot lit with direct current.

The arrow in FIG. 1(b) indicates the magnetization direction of the perpendicularly magnetized film.

Signal recording and overwriting on the magneto-optical medium of the present invention produced in this manner will be explained below.

Here, upward magnetization is assumed to be 1'', and downward magnetization is assumed to be O''.

2 and 3 are partial sectional views for explaining the principle of signal recording and overwriting of the magneto-optical medium of the present invention. The figure is for explaining the principle when recording 0''.

(a) Recording of "■" In FIG. 2, the circular laser spot 1 is traced by lighting the laser with direct current and heating the recording track to a temperature above one Curie.

On the other hand, when recording 111'', the elliptical laser spot 3 is irradiated onto the external magnetic field generation track 7 on which the upward magnetic field has been recorded, and the irradiated portion rises to around the Curie temperature, and the saturation magnetization decreases.Then, the circular laser spot 3 The floating magnetic field 13 of the external magnetic field generating track 8 on which the downward magnetic field was recorded is dominant in the irradiated part of 1, and the circular laser beam 1 of the recording track 5 heated to above Curie temperature is irradiated with Magnetized upward.

In other words, 1" is recorded.

(b) O” record whistle 9ml?
The laser is turned on with direct current, and the recording track is traced while being heated to a temperature above one Curtain temperature.

On the other hand, when recording 0'', the elliptical laser spot 2 is irradiated onto the external magnetic field generation track 8 on which the downward magnetic field has been recorded, and the irradiated portion rises to around the Curie temperature, and the saturation magnetization decreases.Then, the circular laser spot 2 The irradiated portion of 1 is dominated by the floating magnetic field 15 of the external magnetic field generating track 7 in which an upward magnetic field is recorded, and the circular laser spot 1 of the recording track 5 is heated to a temperature of one Curie or higher.
The irradiated part is magnetized downward.

In other words, 10'' has been recorded.

As described above, a binary signal can be recorded on the recording track by selectively irradiating the elliptical spot onto the external magnetic field generating tracks 7.8 provided on both sides of the recording track 5.

Here, the selective irradiation of the elliptical spot can be controlled at high speed, making it possible to record high-frequency signals and high-speed data rates.Also, the external magnetic field generation track and the recording track can be placed adjacent to each other. Since the magnetic field exerted by the floating magnetic field of the external magnetic field generation track on the recording track is strong, the recording track is magnetized regardless of the signal on the recording track, that is, overwriting is possible.

In addition, when recording a signal on the recording track 6, the magnetization direction of the external magnetic field generating tracks provided on both sides is opposite to that of the recording track 5, but this is because, for example, The address number, which is a continuous number, is read during recording, and it is determined whether it is odd or even, and the lighting control of the elliptical spot 2.3 is switched to determine the correspondence between 0 and 1 and the direction of the magnetic field of the write signal to the recording track, regardless of the recording track. It is assumed to be constant.

■Read the address number during playback, determine whether it is odd or even, and switch the polarity of the playback signal.

■Oval spots 2.3 and 110" are placed on the recording track in advance.
11'', that is, the magnetization direction of the external magnetic field generating tracks on both sides, is written in advance, and this information is read during recording, and the direction of the magnetic field of the write signal to the recording track and 110'', 1 are written.
1'' is constant regardless of the recording track.

■Oval spots 2.3, 0″, 1″ on the recording track in advance
That is, the magnetization directions of the external magnetic field generation tracks on both sides are written in advance, and this information is not used during recording but is read during reproduction to switch the polarity of the reproduced signal.

This can be solved by methods such as

In the above embodiment, concentric tracks were explained, but it is also applicable to spiral tracks. In that case, as shown in FIG.
7 in Figure 5.
8 (indicated by a dotted line) indicates an upward magnetic field, and 8 (indicated by a dotted FA line) indicates an external magnetic field generation track in which a downward magnetic field is written in advance.

Further, the outer shape of the medium is not limited to a disk shape, and for example, a card-shaped medium may be driven back and forth.

Further, in this embodiment, the laser beam directed to the external magnetic field generating track is elliptical, but the laser beam is not limited to this.

Furthermore, although binary recording has been described in this embodiment, multi-value recording is also possible as explained below.

Further, in the embodiment, tracks are divided by providing unevenness, but if a three-beam method is used, which allows tracking of the bit string of a signal track, for example, the uneven track is not necessarily necessary.

FIG. 4 is a partial sectional view of the magneto-optical disk of the present invention.
The same symbols as in Figure 2.3 indicate the same effective members.

As shown in Fig. 4, when the circular laser spot 1 is irradiated onto the non-recording rack 5 without irradiating the elliptical laser spot, the left and right sides of the recording track 5 are magnetized in different magnetization directions. ” can be recorded.

In addition, by controlling the power of the laser beam irradiated to the external magnetic field generating track 7.8 and controlling the temperature of the medium,
Multi-level recording is possible by controlling the magnetized area in the vertical direction on the recording track.

(Effects of the Invention) As described above, according to the present invention, high-speed magnetic field modulation can be performed by controlling the irradiation of two laser beams and controlling the direction of the floating magnetic field at high speed, so that high-frequency signals can be overwritten on the magneto-optical medium. It becomes possible.

Furthermore, the irradiation of two laser beams is controlled.
- multivalue recording is also possible.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a magneto-optical disk according to the present invention, FIGS. 2 and 3 are explanatory diagrams showing the recording principle of the magneto-optical disk according to the present invention, and FIG. 4 is a diagram showing the recording principle in the case of multilevel recording. The explanatory diagram, FIG. 5, is an example diagram in the case of a spiral track. (Explanation of symbols of main parts) 1.2.3-...--Laser beam 4---------------Disc substrate 5
．． 6-------・------1-- Recording track?
, 8.9...--External magnetic field generation track Figure 1 (Illll) (b) Figure 2 Figure 3 Figure 4 Figure 5 Procedural amendment (self-initiated May 10, 1985, second display) 1985 Rumored Sacrifice No. 69814 3-2-3 Marunouchi, Chiyoda-ku, Tokyo (411) Nippon Kogaku Kogyo Co., Ltd. 4, Agent @ 140 1-6-3 Nishi-Oi, Honbunagawa-ku, Tokyo King's target drawing G4

Claims (4)

[Claims] (1) A magneto-optical medium characterized in that an external magnetic field generating track is provided on both sides of a recording track, on which perpendicular magnetic fields in different directions are recorded in advance. (2) The magneto-optical medium according to claim 1, which has a disk-like outer shape. (3) The recording track and the external magnetic field generating track are arranged concentrically and alternately, and the external magnetic field generating track is prerecorded with an upward and downward vertical magnetic field alternately. 2. The magneto-optical medium according to item 2. (4) The recording track and the external magnetic field generating track are spiral-shaped, and the external magnetic field generating track is provided on one side of the recording track, and an upward and downward vertical magnetic field is recorded in advance alternately every round. Claim No. 2
Magneto-optical medium as described in Section 1.