JPS6217282B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermomagnetic recording and reproducing apparatus for recording and reproducing information on a magnetic medium having perpendicular anisotropy by heating with a laser spot or the like.

Conventionally, this type of thermomagnetic recording/reproducing means uses MnBi as a recording medium, and utilizes the temperature dependence of the coercive force of its thin film to irradiate a light beam, such as a laser beam, to reverse the magnetization by the heat generated by the spot, thereby producing information. There is a device in which information is read out using the Kerr effect by irradiating the recorded portion with a spot of laser light that does not cause magnetization reversal.

To describe this method in more detail, a temperature-dependent magnetic thin film of manganese bismuth (MnBi) rare earth-iron amorphous alloy or the like is formed on a base by vapor deposition or sputtering, and this thin film is applied to the film surface. A bias magnetic field is applied so that the magnet is magnetized in a certain direction perpendicular to the magnet. Then, the laser beam emitted from the light source is modulated with a recording signal, and the laser beam is irradiated as a spot on the recording medium through the objective lens, increasing the temperature of the irradiated area, thereby lowering the coercive force of the medium and biasing the recording medium. Information is recorded by magnetic reversal when the magnetic field becomes smaller.

Another method is to focus a laser beam on the medium and locally heat the medium to lower the coercive force, and in this state magnetize the medium with a magnetic field that changes according to the recording signal to perform recording. be.

In all such means, the medium is locally heated by the energy of the laser beam to lower the coercive force at the spot, and the magnetic field acting thereon performs thermomagnetic writing.

However, when a medium is actually irradiated with a laser beam, the temperature distribution of the medium is spread out around the center 0 of the laser beam spot, as shown in FIG. This means that magnetization may occur in a relatively wide range around the center 0 of the spot, and the magnetized region will expand accordingly, resulting in a significant decrease in recording density.

Therefore, in order to prevent magnetization reversal caused by laser beam irradiation, for example, it has been considered to apply an external magnetic field to limit the range of magnetization reversal and prevent the enlargement of the magnetized region. It is extremely difficult to control magnetization reversal within a delicate range.

This invention was made to solve the above problems, and an object of the present invention is to provide a thermomagnetic recording and reproducing device that can dramatically increase recording density by providing an auxiliary magnetic pole and converging the magnetic flux applied to the recording medium. With the goal.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an example in which the present invention is applied to a device in which recording is performed by magnetizing a medium using a magnetic field that changes according to a recording signal. In the figure, reference numeral 1 denotes a disk-shaped base, and a magnetic thin film 2 of temperature-dependent manganese bismuth or the like is deposited on this base 1 by vapor deposition or sputtering to form a recording medium. Further, the base 1 is held horizontally and rotated by a motor 3 at a predetermined speed.

On the other hand, reference numeral 4 denotes a light source that generates a laser beam. The laser beam from the light source 4 is applied to a half mirror 6 via a light modulator 5 and a polarizer 51, where it is reflected and passed through a lens 7 to the magnetic thin film 2. I try to give it on my face. In this case, the laser beam is focused on two surfaces of the thin film. Further, an analyzer 8 and a photoelectric conversion element 9 are arranged on an extension line of the optical axis passing through the lens 7 via the half mirror. These analyzer 8 and photoelectric conversion element 9 detect laser light reflected from the two surfaces of the magnetic thin film during reproduction using the Kerr effect.

A signal magnetic field generator, for example a coil 10, is provided above the magnetic thin film 2. This coil 10 generates a magnetic field that changes in response to a recording signal, for example, a digital signal, thereby applying magnetic flux to the portion of the thin film 2 that is heated by the laser beam.

A magnetic auxiliary pole 11 is provided opposite the coil 10 with the base 1 in between. This magnetic pole 11 converges the magnetic flux of the coil 10, and is arranged in contact with the base 1 surface so as to be close to the portion of the magnetic thin film 2 on which the laser beam is focused.

In this case, the auxiliary magnetic pole 11 is made by bonding a ferromagnetic material 13 such as ferrite to a non-magnetic material 121 such as ceramic as shown in FIG. A ferromagnetic material 14 having a relatively high saturation magnetic flux density, such as permalloy or sendust, is attached by sputtering or the like with a thickness of about 1 μm, and another non-magnetic material 122 whose abutting surfaces have been polished in advance is butt-joined. This is obtained by forming an R end face, and in order to improve the convergence of magnetic flux, the ferromagnetic material 13 is extended very close to the R end face to form a magnetic circuit for the magnetic flux coming from the ferromagnetic material 14 on the R end face. I'm trying to minimize the resistance.

In this configuration, as the base 1 rotates, the focal position A of the laser beam and the auxiliary magnetic pole 11 are moved to the position B as shown in FIG. 4 by a moving means (not shown).
It moves in the radial direction of the base 1 to draw a spiral magnetization track c on the surface of the magnetic thin film 2. In this case, the auxiliary magnetic pole 11 is arranged so that the ferromagnetic material 14 on the R end face is located in a direction perpendicular to the magnetization track c.

Next, its effect will be explained. In this case, such an embodiment will be described in which the magnetic field is changed in response to a recording signal, and the medium is magnetized by this magnetic field to perform recording. Therefore, it is assumed here that no modulation operation is performed in the optical modulation device 5.

In this way, when a laser beam is generated from the light source 4, the laser beam is applied to the half mirror 6 via the optical modulator 5 (does not perform a modulation operation) and the polarizer 51, and is reflected there and passes through the lens 7. It is applied to two surfaces of the magnetic thin film through the magnetic thin film. When the laser beam is focused on the thin film 2, this spot is locally heated and the coercive force is reduced. In this state, when a magnetic field is generated from the coil 10 in accordance with the recording signal, the resulting magnetic flux magnetizes the portion of the thin film 2 heated by the spot, thereby recording predetermined information. In this case, the magnetic flux generated by the coil 10 is focused on the extremely narrow (approximately 1 μm) ferromagnetic material 14 portion of the auxiliary magnetic pole 11 and applied to the heated portion of the thin film 2 from the perpendicular direction. Therefore, even if the heated portion of the laser beam spot focused on the thin film 2 spreads, the magnetized region remains the same as the ferromagnetic material 1 of the auxiliary magnetic pole 11.
4, the recording density can be dramatically increased.

Thereby, information is recorded at high density along the magnetization track C as shown in FIG. 4 by rotating the base 1 by the motor 3 in the same manner.

Therefore, with this configuration, the recording density on the recording medium can be dramatically increased, allowing extremely efficient information recording, and since the magnetic flux is converged and used efficiently, the magnetic flux in the coil can be reduced. It is also possible to reduce the energy required for generation.

Next, another embodiment of the invention will be described with reference to FIG. The one shown in FIG. 5 is relatively suitable when, for example, a flexible one with a thin base is used to prevent the magnetic flux density from decreasing due to the magnetic resistance of the base. In this case, the auxiliary magnetic pole 1 was moved as the laser spot moved.
1 in the radial direction of the base 1, and this magnetic pole 11
The ferromagnetic portion of the magnet extends over the entire length of the magnetizable range. As a result, the auxiliary magnetic pole 1
1 movement is unnecessary. The rest is the same as in FIG. 2, and the same parts are given the same reference numerals.

However, even if this method is used, the same effect as described above can be expected.

Further, another different embodiment of the present invention will be described with reference to FIG. 6. The one shown in FIG. 6 is equipped with a motor 12, which moves the entire recording medium including the motor 3, making it unnecessary to move the laser spot or the auxiliary magnetic pole 11. This is what I did. The rest is the same as in FIG. 2, and the same parts are given the same reference numerals.

Even with this arrangement, the same effects as described above can be expected.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications within the scope without changing the gist.
For example, in the above description, recording is performed by magnetizing the medium using a magnetic field that changes according to the recording signal, but a magnetic field generator, that is, a coil 10, generates a constant magnetic field as a bias magnetic field to modulate the laser beam. Even in the system in which the device 5 performs recording and reproduction by modulating the recording signal, high-density recording is possible by converging the magnetic flux caused by the bias magnetic field into an extremely narrow area using the auxiliary magnetic pole and limiting the expansion of the recording area.

As described above, according to the present invention, it is possible to provide a thermomagnetic recording/reproducing device that can dramatically increase the recording density by providing an auxiliary magnetic pole and converging the magnetic flux applied to the recording medium.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the temperature distribution of a laser beam spot, Fig. 2 is a schematic configuration diagram showing an embodiment of the present invention, Fig. 3 is a perspective view of an auxiliary magnetic pole used in the embodiment, and Fig. 4 is a diagram for explaining the temperature distribution of a laser beam spot. The figure is a diagram for explaining the same embodiment, and FIGS. 5 and 6 are schematic configuration diagrams showing different embodiments of the present invention. 1... Base, 2... Thin film, 3, 12... Motor, 4... Light source, 5... Light modulator, 6... Half mirror, 7... Lens, 8... Analyzer, 9...
Photoelectric conversion element, 10... coil, 11... auxiliary magnetic pole.

Claims (1)

[Claims] 1. A disk-shaped recording medium having a magnetic thin film of manganese bismuth, rare earth-iron amorphous alloy, etc., and locally heating this recording medium to reduce the coercive force of the heated portion. means for generating laser light; moving means for moving the laser light generating means in the radial direction of the recording medium; a magnetic field generating device for generating a magnetic field in at least a heated portion of the recording medium; and a scanning direction of the recording medium. an auxiliary magnetic pole having a magnetic thin film thinner than the spot diameter of the laser beam disposed perpendicularly to the magnetic field, and converging the magnetic flux from the magnetic field generator onto the heated portion of the recording medium with the recording medium in between; A thermomagnetic recording and reproducing device comprising: 2. Claims characterized in that the laser beam lowers the coercive force of the heated portion of the medium, and predetermined information is recorded on the medium by a magnetic field according to the recording signal of the magnetic field generator. 2. The thermomagnetic recording and reproducing device according to item 1. 3. Thermomagnetic recording according to claim 1, wherein the magnetic field generating device generates a bias magnetic field and records predetermined information on the medium using a laser beam modulated by a recording signal. playback device.