JPH05120607A - Thermomagnetic recorder - Google Patents

Abstract

PURPOSE:To provide the thermomagnetic recorder having conditions of adequate values of auxiliary magnetic fields which do not generate the unstable phenomenon of recorded information when the thin film of an amorphous alloy magnetic material consisting of a rare earth-transition metal system is used as a recording medium. CONSTITUTION:A rotatable permanent magnet 10 for erasing and permanent magnet 11 for recording for supplying the auxiliary magnetic fields to a magneto-optical disk 8 constituted by forming the thin film of the amorphous alloy magnetic material consisting of the rare earth-transition metal system having the axis of easy magnetization perpendicular to the film plane on a protective plate. The magnitude of the magnetic fields is switched by rotating the permanent magnets at the time of recording and erasing to and from the magneto-optical disk 8. The recording and erasing of the information are executed by heating with a laser beam to the recording medium. The permanent magnets 10, 11 have a bar shape longer than the effective radius of the recording medium and the magnitude of the magnetic fields supplied by the above-mentioned permanent magnets to the above-mentioned recording medium at the time of erasing the information is <=1/3 the coercive force of the recording medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermomagnetic recording device for recording and erasing information by the heat of laser light irradiation.

[0002]

2. Description of the Related Art In recent years, research and development of an optical memory device capable of satisfying demands for high density, large capacity, high speed access, etc. have been actively promoted. Among them, a magneto-optical disk memory that can record, reproduce, and erase information using a semiconductor laser is an image,
It is particularly noted because it can be applied to a file memory for characters and the like or a video disk memory.

Recording on the magneto-optical disk memory is classified into Curie point recording, compensation point recording, and recording utilizing the change in coercive force with temperature. In any of these methods, the temperature of the recording medium (magnetic thin film) is locally raised by using a laser beam or the like with an appropriate external magnetic field applied, and the magnetization of that portion is changed to the direction of the external magnetic field. Recording is so-called thermomagnetic recording.

As shown in FIG. 3 or 4, this thermomagnetic recording method is applied to a magneto-optical disk memory in which a recording magnetic thin film 2 is formed on a transparent substrate 1 such as glass and a protective plate 3 is further provided. When recording, reproducing, and erasing by irradiating the laser beam 4 with the condenser lens 5 for condensing, as shown in FIG.
Alternatively, as shown in FIG. 4, a magnetic field is supplied to the recording magnetic thin film by the permanent magnet 7.

In the case of using the coil 6 as shown in FIG. 3, the required magnetic field can be easily obtained by changing the direction or magnitude of the current flowing through the coil, so that the mechanism is simple. become. However, the recording magnetic thin film 2
In order to supply a magnetic field to the transparent substrate 1, it is necessary to supply a magnetic field to the transparent substrate 1. Therefore, the coil 6 should be as close to the transparent substrate 1 as possible so that the magnetic field supplied to the recording magnetic thin film 2 of the coil 6 is sufficient. It needs to be However, since a very large magnetic field of 100 Oe (Oersted) or more is required on the recording magnetic thin film at the time of recording or erasing in the recording magnetic thin film, the current flowing through the coil 6 is increased or the coil 6 is enlarged. It is necessary to take such measures.

On the other hand, in the case of the system using the permanent magnet 7 as shown in FIG. 4, unlike the system of FIG. 3, the recording magnetic thin film 2 is sandwiched in place of the coil 6 and the side opposite to the condenser lens 5. The permanent magnet 7 is arranged in the magnetic field, and the magnetic field is supplied to the recording magnetic thin film 2 by the permanent magnet 7. Since the permanent magnet can obtain a strong magnetic field even with a relatively small one, the apparatus can be downsized by this method. However, when a permanent magnet is used, a magnetic field is always applied to the recording magnetic thin film, so that the magnitude of the magnetic field of the permanent magnet 7 must be carefully considered.

[0007]

When the material of the recording magnetic thin film 2 is a medium such as MnCuBi, which has a large residual magnetization, the stray magnetic field from the peripheral portion of the recording portion is large, so that an external magnetic field is not required during recording. .. Therefore, a method may be considered in which the permanent magnet 7 is moved away from the recording magnetic substance thin film 2 at the time of recording and the permanent magnet 7 is brought close to the recording magnetic substance thin film 2 only at the time of erasing.

However, the recording magnetic thin film 2 is GdTbF.
e, GdTbDyFe, TbDyFe, GdDyFe,
When a rare earth-iron-based amorphous magnetic material such as TbFe is used, the stray magnetic field from the peripheral portion of the recording portion is small, so that it is necessary to apply external magnetic fields in opposite directions during recording and erasing. Taking a case where a GdTbDyFe film is used as the recording magnetic thin film 2, the GdTbDyFe film has a coercive force of 0.6 kOe to 1.5 kOe and a Curie point of 12
Although the temperature is 0 ° C., an external magnetic field of 100 Oe to 200 Oe is required for recording and 200 Oe to 300 Oe for erasing.
Required an external magnetic field.

When the recording magnetic substance thin film 2 is made of a rare earth-iron type amorphous magnetic substance, an external magnetic field is applied to the recording magnetic substance thin film 2.
It has been found that even if the coercive force is smaller than the coercive force of the above, if it is applied to the recording magnetic thin film 2 for a long time, the recorded information deteriorates at room temperature. For example, when a magnetic field of 300 Oe is applied to the GdTbDyFe film having a coercive force of 0.6 kOe in the direction of magnetization of the recording bit and left for 48 to 72 hours, the recording bit diameter becomes large. On the contrary, the inventors found that the diameter of the recording bit becomes smaller when a magnetic field of 300 Oe is applied in the direction opposite to the magnetization of the recording bit and left standing. The instability phenomenon of the recorded information is caused by the fact that the magnetization of the micro-defects of the magnetic thin film is reversed even in the reverse magnetic field smaller than the coercive force of the magnetic thin film, and the reversal magnetization part gradually expands by the domain wall movement with it as the nucleus. is doing.

The present inventors have confirmed that the recorded information is stable for a long time if the external magnetic field applied to the magnetic thin film is 1/3 or less of the coercive force of the magnetic thin film.

The coercive force of the magnetic thin film changes with temperature, and the rare earth-iron-based amorphous magnetic thin film has the characteristics shown in FIG. In the figure, T _comp is the compensation point, T _comp
c is the Curie point. As shown in the figure, the coercive force of the magnetic thin film changes greatly depending on the temperature. For example, when the room temperature rises by about 10 ° C., the coercive force may drop to about half. Therefore, it has been found that it is necessary to pay attention to the room temperature when the recording medium is composed of the rare earth-iron-based amorphous magnetic thin film.

In summary of the above points, when a rare earth-iron based amorphous magnetic thin film is used as a recording medium, the recording and erasing magnetic fields must be designed with attention to the following points.

To generate a recording magnetic field and an erasing magnetic field in mutually opposite directions.

The recording magnetic field is smaller than the erasing magnetic field.

The erasing magnetic field is 1/3 of the coercive force of the recording medium.
Being below.

The present invention has been made in consideration of the above points, and provides a thermomagnetic recording apparatus capable of applying an optimum external magnetic field when a rare earth-iron-based amorphous magnetic thin film is used as a recording medium. An object of the present invention is to provide a thermomagnetic recording device which is not affected by the permanent magnet for applying an external magnetic field when the device temperature exceeds the stable range of the recording medium or when the power is turned off.

[0017]

In order to achieve the above object, the present invention provides a recording medium by forming a rare earth-iron based amorphous magnetic thin film having an easy axis of magnetization perpendicular to the film surface on a protective plate. The recording medium is provided with a rotatable permanent magnet for supplying an auxiliary magnetic field, and the magnetic field is switched by rotating the permanent magnet at the time of recording and erasing on the recording medium. In a thermomagnetic recording device for recording and erasing information by heating, the permanent magnet has a rod-like body longer than the effective radius of the recording medium, and
In the thermomagnetic recording apparatus, the magnitude of the magnetic field supplied to the recording medium by the permanent magnet when erasing information is 1/3 or less of the coercive force of the recording medium.

[0018]

As described above, the magnitude of the external magnetic field applied to the recording medium at the time of recording and erasing information is set to 1 of the coercive force of the recording medium.
When it is / 3 or less, the recorded information is not affected by the external magnetic field and does not change with time.

[0019]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is an explanatory view of essential parts of an embodiment of a thermomagnetic recording apparatus according to the present invention. In the figure, reference numeral 8 is a magneto-optical disk in which a rare earth-iron based amorphous magnetic thin film is formed on a substrate, and 9 is a motor for rotationally driving the magneto-optical disk 8. The rare earth-iron-based amorphous magnetic thin film is formed in the portion between A and B in the figure (the length of the portion is referred to as the effective radius). Reference numeral 10 is an erasing permanent magnet that generates a strong magnetic field, and 11 is a recording permanent magnet that generates a weak magnetic field.
The erasing permanent magnet 10 is provided on the front side of the magnet holder 12,
The recording permanent magnet 11 is provided on the back side. However, the magnet holder 12 can be rotated by the stepping motor 13, and the erasing permanent magnet 10 and the recording permanent magnet 11 can reverse their positions. Reference numeral 14 is a disk fixed to the magnet holder 12, and holes are formed at appropriate positions on the disk. Reference numeral 15 is a position sensor having a photocoupler therein, which reads the above-mentioned hole by the photocoupler of the position sensor when the disk 14 rotates.
By this reading, the positions of the erasing permanent magnet 10 and the recording permanent magnet 11 are recognized. Since the erasing permanent magnet 10 and the recording permanent magnet 11 form a rod-shaped body having a longer effective radius than the magnetic thin film of the magneto-optical disk 8, the optical head (not shown) moves in the radial direction of the magneto-optical disk. At the same time, it is not necessary to interlock the erasing permanent magnet 10 and the recording permanent magnet 11, and therefore the mechanism for applying the external magnetic field is simple. In the figure, C indicates the laser light irradiation direction of the optical head. 16 is a support plate,
The stepping motor 13 is supported via the shaft 17. The stepping motor 13 has a mechanism capable of rotating about the shaft 17 in the direction of arrow D, and automatically rotates in the direction of arrow D when the temperature of the apparatus exceeds the stable range of the recording medium or when the power is turned off. The erasing permanent magnet 10 and the recording permanent magnet 11 are kept away from the recording medium. Thus, the mechanism is such that the information recorded on the recording medium is not disturbed by the erasing permanent magnet 10 and the recording permanent magnet 11.

[0021]

As described above, according to the present invention, it is possible to apply an optimum external magnetic field when a rare earth-iron-based amorphous magnetic thin film is used as a recording medium, and the information recording state Not only can a stable thermo-magnetic recording device be provided, but the recording medium is not affected by the permanent magnet for applying an external magnetic field when the temperature of the device exceeds the stable range of the recording medium or when the power is turned off. A magnetic recording device can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an embodiment of a thermomagnetic recording device according to the present invention.

FIG. 2 is a diagram showing temperature-coercive force characteristics of a rare earth-iron-based amorphous magnetic thin film.

FIG. 3 is a diagram illustrating an example of a thermomagnetic recording method.

FIG. 4 is a diagram illustrating another example of the thermomagnetic recording method.

[Explanation of symbols]

 1 transparent substrate 2 recording magnetic thin film 3 protective plate 4 laser beam 5 condenser lens 6 coil 7 permanent magnet 8 magneto-optical disk 9 motor 10 erasing permanent magnet 11 recording permanent magnet 12 magnet holder 13 stepping motor 14 disc 15 position Sensor 16 Support plate 17 Axis

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takao Hinata 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Hideka Yamaoka 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Yap Co., Ltd.

Claims (1)

[Claims] 1. A recording medium having a rare earth-iron-based amorphous magnetic thin film having an easy axis of magnetization perpendicular to the film surface formed on a protective plate to provide a rotatable permanent magnetic field for supplying an auxiliary magnetic field to the recording medium. A thermo-magnetic recording apparatus comprising a magnet, wherein the permanent magnet is rotated during recording and erasing on the recording medium to switch the magnitude of the magnetic field, and information is recorded and erased by heating the recording medium with a laser beam. The permanent magnet forms a rod-shaped body longer than the effective radius of the recording medium, and the magnitude of the magnetic field supplied to the recording medium by the permanent magnet at the time of erasing information is 1/100 of the coercive force of the recording medium. A thermomagnetic recording device characterized by being 3 or less.