JPH0439726B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides a method for reducing the coercive force by irradiating light onto the surface of a magnetic medium and increasing the temperature of the light irradiated portion of the medium. The present invention relates to a thermomagnetic recording method in which a magnetic field is applied to a portion and the magnetization direction of the light irradiated portion is set in the direction of the applied magnetic field.

[Technical Background and Problems of the Invention] The thermomagnetic recording method has been attracting attention as a means of obtaining a large-capacity information storage device. This thermomagnetic recording method applies a magnetic field smaller than the coercive force (Hc) of the medium at room temperature to a flat magnetic medium, and irradiates the medium with light focused on a minute diameter, thereby increasing the temperature of the light-irradiated portion of the medium. This method uses the decrease in the coercive force of the medium due to the temperature rise to align the magnetization direction of the light irradiated portion with the direction of the applied magnetic field, and is also called a magneto-optical recording method.

There are two types of thermomagnetic recording methods: vertical thermomagnetic recording, in which the axis of easy magnetization of the medium is perpendicular to the surface of the medium, and magnetization remains in the direction perpendicular to the surface of the medium, and horizontal thermomagnetic recording, in which magnetization remains in the plane of the medium. There is a magnetic recording method. Furthermore, depending on the characteristics of coercive force change due to temperature rise of the medium material, it can be divided into the Kuyuri temperature recording method and the compensated temperature recording method. For example, recording using Tb-Fe material is based on the Currie temperature recording vertical thermomagnetic recording method, recording using Gd-Co material is using the compensated temperature recording type vertical thermomagnetic recording method, and recording using CrO ₂ is using the Cuyuri temperature recording type horizontal thermal recording method. It is a magnetic recording method.

By the way, in any of these methods,
Since recording is performed by focusing the light onto a tiny spot and raising the temperature of the medium, it is characterized by a higher track density than normal magnetic recording, but as a result of recording information in a tiny area, Conventionally, there has been a problem that small defects in media tend to cause errors. In addition, since it is necessary to accurately position in a minute area to perform recording and playback, the optical positioning device becomes complex, requiring a large number of parts and circuit configurations.
There has also been the problem of high prices. Furthermore,
Since the minimum diameter that can be focused is theoretically limited by the wavelength of the light, there is also the drawback that it is difficult to further increase the density.

In terms of recording methods, there are two types: magnetic field bias type, which performs recording by instantaneously irradiating light while applying a constant magnetic field; There is a thermal bias type in which recording is performed using a magnetic field, but the magnetic field bias type requires erasing before new information can be recorded, and the thermal bias type has the disadvantage that it is not possible to increase the recording density.

[Object of the Invention] This invention has been made in view of the above, and its purpose is to provide a thermomagnetic recording method that allows information to be recorded with high density and high reliability. It is about providing.

[Summary of the Invention] In order to achieve the above object, the present invention provides a magnetic medium having a polycrystalline structure with isotropic in-plane magnetization characteristics, and a magnetic medium having a predetermined size at a desired position on the surface of the magnetic medium. A light irradiation means for irradiating condensed light, and magnetization in a desired direction remaining in the plane of the desired position irradiated with light by the light irradiation means, and information is stored according to the direction of the magnetization. In order to achieve this, the present invention includes a magnetic field applying means for applying a magnetic field corresponding to the direction of magnetization at least within the plane of the desired position.

[Embodiments of the Invention] Examples of the invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, a flat quadrilateral magnetic medium 1 is made of an isotropic magnetic material having isotropic magnetization characteristics in the in-plane direction of the medium, such as a polycrystalline γFe ₂ O ₃ thin film, Co-
It is formed of a P-based alloy thin film or the like. Near each side of the magnetic medium 1, rod-shaped orthogonal magnetic field generators 3, 5, 7, and 9 are arranged parallel to each side. Further, the surface of the magnetic medium 1 is irradiated with light from the light source 11 that is deflected by the optical deflector 13 and focused by the condenser 15, and the temperature of the irradiated portion of the magnetic medium 1 is increased. It's summery. As this temperature approaches the Curie temperature of the medium, the coercive force of that portion of the magnetic medium 1 decreases.

The orthogonal magnetic field generators 3, 5, 7, and 9 are each designed to generate a magnetic field in a predetermined direction within the plane of the magnetic medium 1, that is, within the XY plane of the XYZ axes shown in FIG. More specifically, for example, the orthogonal magnetic field generator 3 generates a magnetic field oriented in the positive direction of the Y-axis, the orthogonal magnetic field generator 5 generates a magnetic field oriented in the positive direction of the X-axis, and the orthogonal magnetic field generator 7 generates a magnetic field oriented in the negative direction of the Y-axis. The orthogonal magnetic field generator 9 is designed to generate a magnetic field directed in the negative direction of the X-axis. Then, one of the orthogonal magnetic field generators 3, 5, 7, and 9 is operated under the control of a control device (not shown), and a magnetic field in a predetermined direction is generated in the plane of the magnetic medium 1 by the operated orthogonal magnetic field generator. It is starting to be applied. Further, in this case, two or more orthogonal magnetic field generators may be operated simultaneously to apply a magnetic field to the magnetic medium 1 in a direction formed by combining the magnetic fields generated by both orthogonal magnetic field generators.

In the device configured as described above, in order to store desired magnetic information at a desired position within the plane of the magnetic medium 1, the light from the light source 11 is directed to the optical deflector 13.
and irradiates the surface of the magnetic medium 1 at a desired position by controlling the light condensing device 15, and drives any of the orthogonal magnetic field generators 3, 5, 7, and 9 to generate the driven orthogonal magnetic field generator. A magnetic field generated in a desired direction is applied to the light irradiated portion. Then, the temperature of the portion irradiated with the light rises and the coercive force of the magnetic medium 1 in that portion decreases.
The magnetization of the magnetic medium 1 in this portion is aligned in the direction of the magnetic field applied from the orthogonal magnetic field generator. After arranging the direction of magnetization of the portion in a desired direction in this manner, if light irradiation is stopped, information based on the direction of magnetization will be stored in the portion.

That is, in the thermomagnetic recording device of the present invention, information is stored according to the direction of magnetization. This is because conventional devices store binary information (i.e., 1 bit) using reversal of magnetization in one direction in one unit storage area, that is, a unit storage area that stores one piece of information. On the other hand, in the thermomagnetic recording device of the present invention, information is stored according to the direction of magnetization in one unit storage area, and a large amount of information corresponding to the number of directions of magnetization is stored in one unit storage area. It can be stored in an area, and the storage capacity can be dramatically increased.

More specifically, if the in-plane magnetization direction of the magnetic medium 1 is controlled to be divided into, for example, 16 directions, that is, divided into 16 directions at equal angular intervals of 22.5 degrees and stored, one unit can be stored. The storage area, for example, the smallest unit storage area that is irradiated with the focused light, can store 16 pieces of information, that is, information equivalent to 4 bits, and can store information in 64 directions at equal angular intervals of 5.5 degrees. By dividing it, it is possible to store information equivalent to 6 bits.

Furthermore, in conventional thermomagnetic recording methods, the presence or absence of information was determined based on the strength of magnetization.
Errors could easily occur if there was a local change in the magnetization of the medium, but in the present invention, information is stored in the direction of magnetization, so errors can occur even if there is a change in the magnetization of the medium. It is designed not to cause this. Since the magnetization change of the medium is a type of fluctuation, it is a principle of statistical mechanics that the smaller the target area, the larger the fluctuation.In contrast to conventional methods, errors increase as the density increases. In the present invention, information is stored according to the magnetization direction so that a large amount of information can be stored in one unit storage area.
Errors caused by changes in magnetization of the medium can be reduced.

Next, a method of reading information stored on the magnetic medium 1 in the direction of magnetization as described above will be explained.

There are various methods for this reading, but the apparatus shown in FIG. Analyzers 25 and 27 are analyzers that each correspond to linear polarization, and the rotation of the plane of deflection of light due to the magnetization of the region generated by the magneto-optic effect.
This is detected as an electrical output by light receiving elements 29 and 31 made of, for example, phototransistors, and the angle, that is, the direction of magnetization in the region, is detected from both outputs. Now, for example, if the directions of irradiation with two linear polarizations A and B are orthogonal, and these directions are the X and Y directions, and the magnetization direction of the magnetization M is the θ direction when viewed from the X direction, then the magnetization in the X direction is Rotation of the deflection plane similar to that when the magnetization in the Y direction is M·sinθ and M·cosθ occurs in the linear polarizations A and B, and the light receiving elements 31 and 29
It can be detected as X output and Y output. Therefore,
If the outputs of the linear deflections A and B are expressed orthogonally, the magnetization direction can be determined. Furthermore, although the individual electrical outputs themselves are affected by fluctuations in magnetization M, the magnitude of magnetization can be determined by the following equation, so it can be standardized.

M = [(M・sinθ) ² + (M・cosθ) ² ] ^1/2 = [(A output) ² + (B output) ² ] ^1/2 In the end, even if there are fluctuations in magnetization, the A output and The magnetization direction can be completely detected from the B output. In the above embodiment, the case where the two independent linear deflections are orthogonal was explained, but unless the two linear deflections are parallel, the two outputs can be processed by post-processing such as circuit processing. It is possible to detect the magnetization direction.

Furthermore, in order to store desired information, that is, magnetization in a desired direction, at a desired storage position of the magnetic medium 1,
As shown in FIG. 1, a magnetic field in an arbitrary direction is generated using a Helmholtz coil or the like disposed outside the magnetic medium 1, and a suitable optical deflection device such as a galvanometer mirror or an ultrasonic deflector is used. Alternatively, the orthogonal magnetic field generator and the optical system may be integrated and formed smaller than the medium, and this may be positioned to irradiate the magnetic medium 1 with light at a desired position using a device. The storage position may be determined by relative movement.

FIG. 3 shows another embodiment of the present invention constructed in this manner. In the figure, a disk-shaped magnetic medium 33 is used, and this disk-shaped magnetic medium 33 is rotated by a spindle motor 35. And this magnetic medium 3
A device 37 that integrally combines the above-described orthogonal magnetic field generator and an optical system is disposed adjacent to the lower side of the lower surface of 3. It is configured to be able to move in the radial direction of the medium 33. As a result, as in a normal magnetic disk device, the actuator 39 determines the position of the device 37 with respect to the radial track of the magnetic medium 33, and the rotation of the magnetic medium 33 by the spindle motor 35 determines the position with respect to the sector in the circumferential direction. If the storage position on the magnetic medium 33 is determined by the following steps, information can be read and written at relatively high speed even in the case of a large capacity.

The orthogonal magnetic field generator housed in the device 37 described above includes a pair of magnetic poles 43 and 45 disposed close to one side of the magnetic medium 33 as shown in FIG. A pair of magnetic poles 43, 4
The magnetic pole 4 is configured to generate a magnetic field in a direction perpendicular to the direction of the magnetic field 5 in the plane of the magnetic medium 33, for example.
For example, another pair of magnetic poles are arranged perpendicularly to the magnetic poles 43 and 45, and magnetic field generating windings 47 and 49 are wound around the magnetic poles 43 and 45, and magnetic field generating coils 47 and 49 are similarly wound around the magnetic poles (not shown). It is configured by winding a winding so that a composite magnetic field is applied to the magnetic medium 33 from one side of the magnetic medium 33. In this case, a complete in-plane magnetic field is not generated for the magnetic medium 33, but since it is approximately parallel to the plane of the magnetic medium 33 on the center line 51 of the magnetic field generator, this portion can be used to All you have to do is irradiate the area with light. As mentioned above, a large amount of information can be stored in one unit storage area, and the area to be stored at one time may be large, so positioning does not require much precision and the configuration of the positioning device is simple. be.

Further, since the orthogonal magnetic field generator only needs to be able to generate a magnetic field of a predetermined magnitude in any direction within the plane of the magnetic medium 33, it does not need to have a symmetrical structure. It should be generated from the gap corresponding to the gap in the head. Then, this gap, that is, the magnetic pole 43,
If the gap between 45 and 45 is configured to be several hundred μ or less, and the magnetic poles 43 and 45 at the tips of the gap are placed close to the surface of the magnetic medium 33 at about half the gap length, a magnetic field of about 1000 Oe can be generated. However, similar to magnetic heads, this magnetic field can be reversed at high frequencies. Then, by controlling the current flowing through the magnetic field generating windings 47 and 49 while continuously irradiating light toward the magnetic medium 33 from the gap between the magnetic poles 43 and 45, the direction of magnetization can be determined. This makes bias type recording possible. In this case, the conventional thermal bias type had the disadvantage of not being able to achieve high recording density as described above, but in the present invention, the recording density can be increased by increasing the number of magnetization directions without reducing the unit recording area. High-density recording is now possible. Therefore, the optical system is simple, and even if there is already recorded information, new information can be stored thereon.

Note that the method of determining the direction of the magnetic pole is not limited to the method of combining magnetic fields as in the above embodiment; for example, it is also possible to rotate a magnetic field generator to direct the magnetic field in an arbitrary direction. can.

[Effects of the Invention] As explained above, according to the present invention, a magnetic medium having a polycrystalline structure with isotropic in-plane magnetization characteristics is used, and information is generated by the direction of the in-plane residual magnetization of this magnetic medium. By simply increasing the direction of magnetization in the unit storage area, high-density recording can be performed without reducing the unit storage area, and there is no need to make the unit storage area smaller. Therefore, the configuration of peripheral devices such as an optical system and a positioning device can be simplified. In addition, there is no need to reduce the unit storage area, and information is stored based on the direction of magnetization, rather than using magnetization reversal or strength as in the past, so errors can occur even if magnetization changes. First, a highly reliable storage device is possible.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a thermomagnetic recording device showing an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a reproducing device for the thermomagnetic recording storage shown in FIG. 1, and FIG. Fig. 4 is a partial block diagram of an orthogonal magnetic field generator used in the apparatus of Fig. 3; DESCRIPTION OF SYMBOLS 1... Magnetic medium, 3, 5, 7, 9... Orthogonal magnetic field generator, 11... Light source, 13... Optical deflector, 15... Light condensing device.

Claims (1)

[Claims] 1. A magnetic medium having a polycrystalline structure with isotropic in-plane magnetization characteristics, a light irradiation means for irradiating light focused to a predetermined size onto a desired position on the surface of the magnetic medium, and the light irradiation means. causing magnetization in a desired direction to remain in the plane of the desired position irradiated with light by the means;
A thermomagnetic recording system comprising a magnetic field applying means for applying a magnetic field corresponding to the direction of magnetization within a plane at least at the desired position in order to store information according to the direction of magnetization.