JPS61105746A - Thermal magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To largely increase the recording density by rotating a recording medium, moving it in the direction of the radius of the rotation and focusing magnetic flux given to the recording medium by an auxiliary magnetic pole. CONSTITUTION:The laser beam from a beam source 4 focuses on a magnetic thin film 2 of a recording medium through a light modulating equipment 5 and a lens 7, heats the medium partially and reduces its magnetic resistance. A magnetic field is generated by a coil 10 in response to a recording signal, and its magnetic flux magnetizes a thin film 2 in the heated spot to record certain information. A magnetic field generating equipment 11 consists of a nonmagnetic material 121 and a ferromagnetic material 13 joined together, and the surfaces are formed into a ferromagnetic material 14 of 1mu thickness. As the magnetized area is limited to a very small area of the ferromagnetic material 14 of the magnetic field generating equipment 11 although the heated area is rather large, the recording density of a spiral-type magnetic track formed by the rotation of a base 1 with a motor 3 can be largely increased.

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, as this type of thermomagnetic recording/reproducing means, for example, Mn
Using B + as a recording medium, the temperature dependence of the coercive force of the thin film is used to irradiate a light beam, such as a laser beam, and the heat generated by the spot causes magnetization reversal to record information, and to reproduce information, which causes magnetization reversal. There is a device in which the recorded area is irradiated with a spot of laser light that is small enough to cause the recording area to read out information using the Kerr effect.

In other words, to be more specific, such a method can be applied to Mn.
A magnetic thin film such as B1 or rare earth-iron amorphous alloy is formed on the base by vapor deposition or sputtering, and a bias magnetic field is applied so that the thin film is magnetized in a certain direction perpendicular to the film surface. 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 an objective lens to increase 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 field becomes smaller than the magnetic field.

In addition, the laser beam is focused on the medium to locally heat the medium and reduce the coercive force.

In this state, the medium is magnetized by a magnetic field that changes according to the recording signal to perform recording. There are five methods.

In all of these 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 centered on the center 0 of the spot, and the magnetized region will expand accordingly and the recording density will drop significantly.

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 provides a thermomagnetic recording and reproducing device that can dramatically increase recording density by converging magnetic flux applied to a recording medium using an auxiliary magnetic pole. The purpose is to

An embodiment of the present invention will be described below with reference to the drawings. Second
The figure shows the principle of thermomagnetic recording according to the present invention, and shows an example of application 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 1
1 is a disk-shaped base, and a magnetic thin film 2 of MnB1 or the like is deposited on this base 1 by vaporization 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, 4 is a light source that generates a laser beam, and the laser beam from this light source 4 is transmitted through a light modulator 5 and a polarizer 51.
-7 Mirror 6-Here, the light is applied to the surface of the magnetic thin film 2 via the reflecting lens 7. 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 through the mirrors . These analyzer 8 and photoelectric conversion element 9 are connected to the reproduction time sensitive thin film 2.
Laser light reflected from a surface is detected 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 according to a recording signal, for example, a digital signal.
The resulting magnetic flux is applied to the thin film 2 portion heated by the laser beam.

The generator 11 converges the magnetic flux of the coil 10, and is disposed in contact with the base 1 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 magnetic field generating device 11 is configured as shown in FIG.
3 are joined, and then the abutted end surfaces are optically polished, and a ferromagnetic material 14 with a relatively high saturation magnetic flux density such as Perm 2 or Sendust is attached to this surface with a thickness of about 1 μm by sputtering, and the abutted end faces are further abutted in advance. It is obtained by butt-joining another non-magnetic material 122 whose surface has been polished, and then forming an R end surface.In order to improve the convergence of magnetic flux, the ferromagnetic material 13 is extended very close to the R end surface. Thus, the resistance of the magnetic circuit to the magnetic flux entering from the ferromagnetic material 14 on the R end face is reduced.

In addition, in such a configuration, by 10 rotations of the base, the focal position A of the laser beam and the magnetic field generation pattern 1 are changed as shown in FIG.
1 is moved in the direction B shown in the figure, that is, in the radial direction of the base 1, so that a spiral magnetic ratio track C is drawn on the surface of the magnetic thin film 2.

In this case, the magnetic field generating device 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.

Explain the action of the arrow. 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 transmitted to the optical modulator 5 (which does not perform a modulation operation).
, is applied to the half mirror 6 via the polarizer 51, reflected there, and applied to the magnetic thin film 2 via the lens 7. 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 # film 2 portion heated by the spot, thereby recording predetermined information. In this case, the magnetic flux generated by the coil 10 is molecularly focused on the extremely narrow (approximately 1 μm) ferromagnetic material 14 of the magnetic field generating device 11 and is applied to the heated portion of the thin film 2 from the perpendicular direction. Therefore, even if the heated part of the laser beam spot focused on one thin film 2 spreads, the delivery area is the magnetic field generator】1
Since the recording density is limited to an extremely narrow portion of the ferromagnetic material 14, the recording density can be dramatically increased.

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

Therefore, with this configuration, the recording density on the recording medium can be dramatically increased, so information can be recorded extremely efficiently.In addition, since the magnetic flux is converged and used efficiently, it is possible to dramatically increase the recording density on the recording medium. It is also possible to reduce the energy required to generate magnetic flux.

An embodiment of this invention will be described with reference to FIG.
2 is provided, thereby moving the entire recording medium including the motor 3, making it unnecessary to move the laser spot or the magnetic field generator 11. The rest is the same as in FIG. 2, and the same parts are given the same reference numerals.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be modified and applied as appropriate without changing the gist. For example, in the above description, a method was described in which recording is performed by arsenizing the medium using a magnetic field that changes depending on the recording signal intensity. However, a magnetic field generator, that is, a coil 10, generates a constant magnetic field as a bias magnetic field and modulates 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 generated by the bias magnetic field into an extremely narrow area using the magnetic field generator and limiting the spread of the recording area. Furthermore, although a disk-shaped medium is used in the above description, a drum-shaped medium may also be used.

As described above, according to the present invention, it is possible to provide a thermomagnetic recording and reproducing apparatus that can dramatically increase the recording density by providing a magnetic field generating device and focusing 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 figures are a partial diagram for explaining the same embodiment, and a fifth diagram is a schematic structural diagram showing a different embodiment of the present invention. 1...Base 2...Thin film 3.12...
Motor 4...Light source 5...Light modulation device
6...--7 Mirror 7-Lens 8.
・Analyzer 9...Photoelectric conversion element 10...Coil 11...
magnetic field generator

Claims (1)

[Claims] A recording medium, a means for generating a laser beam that locally heats the medium, and a magnetic field that generates a magnetic field in at least a heated portion of the medium, the magnetic field being disposed on the front side and/or the back side of the recording medium. 1. A thermomagnetic recording and reproducing apparatus comprising: a generating means; and a driving means for rotating the recording medium and moving the recording medium in a radial direction of rotation.