JPH0679392B2 - Magneto-optical erasing method - Google Patents

Description

The present invention relates to a magneto-optical erasing method used for initializing a magneto-optical recording medium for recording / reproducing with a light beam and erasing information.

[Conventional technology]

Conventionally, polycrystalline thin films such as MnBi, MnCuBi, GdCo, GdFe, T
The following three methods are used as a method for aligning the magnetization direction of a magneto-optical recording medium having an easy axis of magnetization perpendicular to the film surface such as an amorphous thin film of bFe, TbFeCo, etc. in one direction to perform medium initialization and information erasure. It has been known.

One is a method of applying a magnetic field higher than the coercive force of the medium to the medium at room temperature to align the magnetization direction of the medium in one direction, that is, upward or downward with respect to the medium surface.

The second method is to apply a supplemental magnetic field of several hundred Oe to the medium in the same manner as in the case of performing magneto-optical recording in a magneto-optical recording device for recording with a light beam, and focus it on the medium. This is the method of irradiating the laser beam. For example, FIG. 3 is a sectional view of a portion related to the erasing operation in the conventional magneto-optical recording / reproducing apparatus disclosed in JP-A-57-18038, in which (1) is a magneto-optical recording. A disk, (5) a motor for rotating the disk,
(6) is a spindle, (7) is a magneto-optical head, (8) is a laser device, (9) is a polarized beam splitter, (10)
Is a condenser lens, and (11) is an exciting coil. Next, the erase operation will be described. First, laser beams are emitted from two laser devices (8), and both laser beams are combined by a polarized beam splitter (9), and a condenser lens (1
It is focused on the magneto-optical recording disk (1) which is rotated by the motor (5) via (0). As a result, the magnetic thin film corresponding to the converging point on the circular plate (1) rapidly rises in temperature and its coercive force sharply decreases. Therefore, if a magnetic field of several hundred Oe is applied to the disk (1) by the exciting coil (11), the magnetization of the magnetic thin film is aligned in one direction, and an erasing operation is performed. Erasing is performed in a ring shape, but if the magneto-optical head (7) is moved in the radial direction of the disc (1), it is erased in a spiral shape.

A third method is to install the magneto-optical recording medium in a constant temperature bath or the like, hold it at about 200 ° C. to reduce the holding power, and then apply a magnetic field of about several hundred Oe.

[Problems to be solved by the invention]

However, in the case of the first method, the coercive force of the magneto-optical recording medium is several KOe or more, and when a rare earth transition metal alloy amorphous thin film in the vicinity of the magnetically compensating composition is used, the coercive force is several tens of KOe. More than that. Therefore, in order to apply a magnetic field higher than the coercive force of the medium, an electromagnet capable of flowing a large current must be used, which has a drawback of increasing the size of the device.

The second method has a drawback that it takes a long time to erase all the recording tracks on the disk. For example,
The radius of the disk (1) is 65 mm, the recording track is at intervals of 1.6 μm from the radius of 30 mm to the radius of 55 mm, and the disk rotation speed is 1800 rpm.
In this case, it takes about 9 minutes to erase all tracks.

Further, in the third method, when a resin such as polycarbonate or polymethylmethacrylate is used as the substrate of the magneto-optical recording medium, there is a problem that the substrate is deformed by heat. This invention has the above problems. This is done to solve the problem, and it is possible to erase the entire magneto-optical recording medium in a short time, and it is possible to erase while preventing deformation of the magneto-optical recording medium. The purpose is to obtain an effective magneto-optical erasing method.

[Means for solving problems]

The magneto-optical erasing method of the present invention includes a temperature raising step of irradiating the entire magneto-optical recording medium having an easy axis of magnetization in a direction perpendicular to the film surface with a flash light source to raise the temperature, and a temperature raising step. A magnetic field is applied to the magneto-optical recording medium by applying a magnetic field having a coercive force or more in the direction perpendicular to the medium surface so that the magnetization direction of the magneto-optical recording medium is aligned in one direction.

[Action]

In the present invention, the entire magneto-optical recording medium is irradiated with light by a flash light source to raise the temperature of the medium magnetic thin film for a very short time to reduce the coercive force, and the magnetic field above the reduced coercive force reduces the magnetic force of the medium magnetic thin film. Since the erasing operation is performed by aligning the magnetizations in one direction, the erasing and especially the initialization of the magneto-optical recording medium can be performed in a short time, and the temperature rise of the magnetic thin film is short, so the temperature rise of the substrate is small and the softening temperature is low. It is possible to use a substrate having a low power consumption.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a characteristic diagram showing the temperature change of the coercive force typical for the magneto-optical recording medium used in the examples. Coercive force at room temperature is 9KOe
At about 180 ° C, the coercive force is about 400 Oe.

FIG. 1 is a sectional view of a magneto-optical erasing device to which an embodiment of the present invention is applied. (1) is a magneto-optical recording medium, (2) is a reflecting mirror, (3) is a flash light source, and (4) is It is an electromagnet.

The erase operation starts with 500 Oe on the entire surface of the magneto-optical recording medium (1).
A current is passed through the electromagnet (4) so that the above vertical magnetic field is applied. Next, the entire surface of the magneto-optical recording medium is irradiated with light from the light source (3). The temperature of the medium magnetic thin film
By increasing the temperature to 180 ° C or higher, the coercive force of the medium decreases to 500 Oe or less, and the magnetization of the medium magnetic thin film is aligned in the direction of the applied magnetic field. Information recorded as a magnetization pattern on the magneto-optical recording medium (1) is erased. It

As described above, according to the present invention, since the flash light source (3) capable of instantly emitting a large amount of light energy is used as the light source, the light irradiation time required to raise the temperature of the entire magnetic thin film of the medium can be shortened. It is possible to prevent the temperature rise of the substrate of the magnetic recording medium.

Further, the applied magnetic field can achieve the intended purpose if it is applied only during the irradiation of light.

Further, in the above embodiment, the electromagnet (4) is used to apply the magnetic field.
However, a permanent magnet may be used instead of the electromagnet.

In the above embodiment, the case where the recorded information is erased is explained, but the magnetization of the magneto-optical recording medium in the demagnetized state immediately after being formed by the vapor deposition method is aligned in one direction for initialization. It goes without saying that the case can be performed by the same procedure as in the above embodiment and is particularly efficient.

The magnitude of the applied magnetic field, the light irradiation intensity, and the light irradiation time can be appropriately selected by the user according to the temperature characteristics of the coercive force of the magneto-optical recording medium to be erased.

〔The invention's effect〕

As described above, the present invention provides a temperature raising step of irradiating the entire magneto-optical recording medium having an easy axis of magnetization in a direction perpendicular to the film surface with a flash light source to raise the temperature, and a temperature raising step. The entire magneto-optical recording medium is subjected to a magnetic field applying step of applying a magnetic field in the direction perpendicular to the medium surface, which is not less than the coercive force, to the magneto-optical recording medium so that the magnetization directions of the magneto-optical recording medium are aligned in one direction. Can be erased in a short time and can be erased while preventing deformation of the magneto-optical recording medium, and in particular, a magneto-optical erasing method effective for initializing the magneto-optical recording medium can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a magneto-optical erasing device to which an embodiment of the present invention is applied, and FIG. 2 is a characteristic diagram showing temperature change of coercive force of a magneto-optical recording medium according to an embodiment of the present invention. FIG. 1 is a sectional view of a portion related to an erasing operation of a conventional magneto-optical recording / reproducing device. In the figure, (1) is a magneto-optical recording medium, (2) is a reflecting mirror, (3) is a flash light source, and (4) is an electromagnet. In the drawings, the same reference numerals indicate the same or responsible parts.

Claims (1)

[Claims] 1. A heating step of irradiating a whole of a magneto-optical recording medium having an easy axis of magnetization in a direction perpendicular to a film surface with a flash light source to raise the temperature, and a coercive force equal to or higher than a coercive force at the elevated temperature. A magneto-optical erasing method in which a magnetic field in a direction perpendicular to the medium surface is applied to the magneto-optical recording medium to align the magnetization direction of the magneto-optical recording medium in one direction.