JPS5923014B2 - Magneto-optical recording and reproducing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a magneto-optical recording and reproducing method, and in particular, a magnetic layer made of a magnetic material with high coercive force and a magnetic thin film made of a magnetic material with low coercive force are brought into close contact with each other. The present invention relates to an improvement in a magneto-optical recording and reproducing method in which high-density recording is performed by applying an external magnetic field to a combined magnetic recording layer and irradiating a light beam.

This type of magneto-optical recording method originally uses an extremely small spot of a light beam such as a laser beam to locally change the temperature of a minute area in the magnetic layer, and modulates the applied magnetic field or the intensity of the irradiated light beam using an information signal. This system is designed to perform high-density thermomagnetic recording in a pattern corresponding to an information signal.

On the other hand, magnetic powder-coated magnetic layers with high coercive force, which are suitable for high-density magnetic recording because it is easy to obtain a homogeneous magnetic layer, scatter light beams due to their powdery nature. As a result, the irradiation spot becomes blurred, making it difficult to perform high-density recording and reproduction, especially reproduction, with sufficiently satisfactory performance using a light beam. However, the conventional magneto-optical recording method for a magnetic recording medium in which such a magnetic powder-coated magnetic layer is provided on a transparent base in the form of a film or sheet is as shown in FIGS. 1 to 3. However, due to the different configurations and arrangements used, fully satisfactory results could not be obtained in either case.

That is, in the magneto-optical recording and reproducing method having the configuration shown in FIG. At the same time, a magnetic field is applied to the magnetic layer 2.
The laser beam 3 is converged and irradiated by a lens 9 onto the magnetic field application area of The structure is the same as that shown in FIG. 1, except that the direction of beam irradiation is changed and reproduction is carried out magnetically only by another magnetic head 5.

However, in the conventional magneto-optical recording and reproducing method shown in FIG. 1, at least the application of a magnetic field and the irradiation of a light beam during recording are performed separately on both the front and back surfaces of the magnetic recording medium. Since this involves loss, it is difficult to perform high-density recording, and since the conventional methods shown in FIGS. 1 and 2 both use contact-type magnetic heads, the above-mentioned Not only is it necessary to separate the magnetic field application from the light beam irradiation, as in the case of Ta. Furthermore, in these magneto-optical recording and reproducing methods, since the magnetic powder-coated magnetic layer 2 is directly irradiated with a light beam, the irradiated spot is blurred due to the aforementioned scattering of the light beam, which poses a problem especially during reproduction. Therefore, as shown in the example shown in the second figure, there is a drawback that magnetic reproduction must be performed only by a magnetic head. In order to solve the problem of light beam scattering caused by the magnetic layer 2 coated with magnetic powder, in the conventional magneto-optical recording and reproducing method configured and arranged as shown in FIG. A magnetic powder-coated magnetic layer 2 is provided on a low coercive force magnetic thin film 6 formed by vapor deposition or the like with good granularity.
Recording is performed by applying an external magnetic field with the magnetic head 4 in contact with the magnetic layer 2, and a minute area of the magnetic thin film 6 magnetized corresponding to the magnetized area of the magnetic layer 2 is irradiated with the laser beam 3. The resulting reflected light beam is extracted through a lens 9 for magneto-optical reproduction.

In the conventional magneto-optical recording and reproducing method shown in FIG. 3, since the magnetic powder-coated magnetic layer 2 is not directly irradiated with the light beam 3, the above-mentioned problem due to scattering of the light beam does not occur. Since the external magnetic field is applied by a magnetic head, similar to the conventional method shown in Figs. In addition, the above-mentioned light beam scattering caused by the incident light beam transmitted through the magnetic thin film 6 reaching the magnetic layer 2 cannot be avoided. However, it has been difficult to perform high-density magneto-optical recording and reproduction with sufficient performance. The object of the present invention is to eliminate the above-mentioned drawbacks and difficulties of the prior art, and to fully satisfy the problem without deterioration in performance due to separation loss between magnetic field application and light beam irradiation or contact between magnetic heads. The object of the present invention is to provide a magneto-optical recording and reproducing method that enables high-density recording and reproducing with the performance that is possible.

That is, the magneto-optical recording and reproducing method of the present invention uses a hollow annular magnetic head to apply an external magnetic field to eliminate separation loss from light beam irradiation, and uses a magnetic powder-coated magnetic layer with high coercive force and a low coercive force. A metal thin film is interposed between the magnetic thin film to prevent the light beam transmitted through the magnetic thin film from reaching the magnetic powder coated layer to prevent the light beam from scattering, and to reflect the incident light beam to prevent light from the magnetic thin film. It is designed to improve the performance of magnetic reproduction, and a magnetic layer made of a magnetic material with high coercive force is provided on the substrate, a thin metal film serving as a reflecting mirror is provided on the magnetic layer, and the above-mentioned A magnetic field is applied to a magnetic recording medium provided with a low coercive magnetic thin film having a higher temperature diffusivity than the magnetic layer and a light beam is applied to at least the magnetic thin film from the side where the magnetic thin film is provided. By conducting the generated heat to the magnetic layer through the metal thin film, the intensity of at least one of the magnetic field and the light beam is changed according to the information signal, and the information signal is recorded in the magnetic layer, and the reflected light is The present invention is characterized in that the information signal is reproduced by detecting changes in the intensity of the beam.

Hereinafter, the present invention will be explained in detail with reference to embodiments with reference to the drawings.

In the embodiment of the magneto-optical recording and reproducing method of the present invention having the configuration shown in FIG. 4, a magnetic thin film 6 made of a magnetic material with low coercive force, such as iron, is formed by vapor deposition or the like on a transparent substrate 7 made of a glass plate or the like. A metal thin film 8 of, for example, silver is deposited on the magnetic thin film 6.

On the other hand, a magnetic powder-coated magnetic layer 2 of chromium oxide CrO2 or the like is applied to a base 1 made of a polymeric synthetic resin material, etc., so that the magnetic layer 2 and the metal thin film 8 mentioned above are in contact with each other. The magnetic thin film 6 and the magnetic powder-coated magnetic layer 2 are disposed facing each other and brought into close contact with each other by well-known and commonly used means to form a magnetic recording medium having a structure in which the magnetic thin film 6 and the magnetic powder-coated magnetic layer 2 are in close contact with each other with the metal thin film 8 interposed therebetween.
In a magnetic recording medium having such a structure, the magnetic thin film 6 and the magnetic layer 2 are in close contact with each other over a wide area with extremely small uniform intervals, and because the thin film 6 and the magnetic layer 2 are formed extremely thinly by vapor deposition or the like between them, the thickness is small. It conducts heat well in the horizontal direction, but makes it difficult to conduct heat in the area direction, and has a structure in which a metal thin film that forms a good reflective surface is closely interposed on both sides. For a magnetic recording medium having such a configuration, a magnetic head 4 configured in a hollow annular shape as shown in the figure is arranged close to and spaced apart from the transparent substrate 7 side, and a magnetic field is generated over a wide range and sufficiently reaches the magnetic layer 2. At the same time, the same transparent substrate 1
A laser beam 3 is incident from the above-mentioned side through the hollow part of the magnetic head 4 so as to be focused by a lens 9 on the interface between the magnetic thin film 6 and the metal thin film 8 located at the center of the applied magnetic field. let In the configuration shown in FIG. 4, the incident laser beam 3 causes the temperature of a small area of the magnetic thin film 6 and the metal thin film 8 in close contact with the magnetic thin film 6 to locally rise rapidly, and the metal is heated by heat conduction from the heated area. The temperature of the minute area of the magnetic layer 2 coated with magnetic powder that is in close contact with the thin film 8 also increases.

Since the magnetic layer 2 is made of a magnetic material with high coercive force that can be easily magnetized even in a relatively weak magnetic field due to such a temperature increase, the laser beam in the magnetic field from the magnetic head 4 described above can be easily magnetized even in a relatively weak magnetic field. High-density thermomagnetic recording of information signals can be performed in a minute area comparable to the convergence spot diameter of the beam 3 by modulating the applied magnetic field intensity or the incident light intensity. When the magnetic layer 2 is magnetized in a pattern according to the information signal as described above, the magnetization pattern is transferred to the magnetic thin film 6 that is in close contact with the magnetic layer 2 through the extremely thin non-magnetic metal film 8. Therefore, when reproducing a recorded signal from a magnetic recording medium on which thermomagnetic recording has been performed as described above, the metal is irradiated with the laser beam 3 in the same manner as during recording. thin film 8
Magneto-optical reproduction is performed by the magneto-optic effect produced by the transfer magnetization of the magnetic thin film 6 of the specularly reflected light from the magnetic field, that is, the magnetic Kerr effect or Farade effect.

In such magneto-optical reproduction, the metal thin film 8 acts as a reflecting mirror for the readout light beam, not only increasing the magneto-optic effect for reproduction and improving reproduction efficiency, but also preventing the magnetic powder from being applied to the layer coated with magnetic powder. The special effect of blocking the transmission of the light beam and preventing the performance deterioration due to the above-mentioned light beam scattering can be obtained. As the magnetic layer 2 in the above-described configuration shown in the fourth figure, a magnetic powder-coated magnetic layer having a high coercive force and a relatively low Curing temperature, such as chromium oxide CrO2 having a Curing temperature of 130° C., is used, and a magnetic thin film is used. As the magnetic layer 6, a magnetic thin film having a thickness of about 500λ, for example, made of a magnetic material such as iron, which has a higher Curing temperature than the magnetic layer 2 and has a low coercive force of about 50 oersted or less, is used; When an extremely thin metal film with good reflectance, for example a silver thin film with a film thickness of 300λ, was used as the metal thin film 8, high density recording with a bit diameter of about 10 μm or less could be performed.

In addition, only the magnetic thin film 6 has a different structure from the above-described structure, and is made of a magnetic thin film that is transparent to the wavelength of the irradiated laser beam 3 during recording and has an extremely low coercive force of about 10 oersted or less, for example, Even when a magnetic garnet thin film of 1 μm was used, high-density recording and reproduction similar to that described above could be performed. As is clear from the above description, according to the present invention, recording and reproducing information signals on a high coercive force magnetic recording medium having a magnetic layer coated with magnetic powder are both performed magneto-optically using a laser beam. Not only can it achieve high-density recording and playback with sufficient performance, it can also perform completely contactless recording and playback, so it can be applied to improving the reliability of memory systems. .

Furthermore, in a recording method that utilizes a temperature change in the magnetic properties of a magnetic recording medium, generally speaking, the steeper the temperature change of the magnetic recording medium, the higher the recording speed is possible. Magnetic powder coated magnetic layer 2 in configuration arrangement
Comparing the thermal diffusivity of the magnetic thin film 6 made of a vapor-deposited film or the like, the former has a thermal diffusivity of about 10-3 cd/S, while the latter has a thermal diffusivity of about 10-1 cd/S. The latter, that is, the magnetic thin film 6
Since the temperature changes much more rapidly in the magnetic thin film 6, as mentioned above, if the temperature change is first caused in the magnetic thin film 6 very efficiently through the intervention of the metal thin film 8, the temperature change due to the laser beam irradiation can be caused extremely rapidly. Thermomagnetic recording can be performed. Therefore, the magneto-optical recording and reproducing method of the present invention provides high speed,
The present invention realizes a highly reliable recording and reproducing device that is capable of high-density magnetic recording and high-speed access, and can be applied to a wide range of technical fields, such as image recording and reproducing devices for editing. can.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing the arrangement of a conventional magneto-optical recording and reproducing method, respectively, and FIG. 4 is a cross-sectional view showing an example of the arrangement of the magneto-optical recording and reproducing method of the present invention. 1...Base, 2...Magnetic layer, 3...
... Laser light beam, 4, 5 ... Magnetic head, 6 ... Magnetic thin film, 7 ... Transparent substrate, 8 ... Metal thin film, 9,9/...Lens.

Claims (1)

[Claims] 1 A magnetic layer made of a magnetic material with high coercive force is provided on a substrate, a thin metal film forming a reflecting mirror is provided on the magnetic layer, and a thin metal film with a low coercive force having a higher temperature diffusivity than the magnetic layer is provided on the thin metal film. A magnetic field is applied to a magnetic recording medium provided with a magnetic thin film from the side on which the magnetic thin film is provided, and a light beam is irradiated to transfer the heat generated in at least the magnetic thin film to the magnetic layer through the metal thin film. By conduction, the intensity of at least one of the magnetic field and the light beam is changed according to the information signal, the information signal is recorded in the magnetic layer, and the information signal is reproduced by detecting the change in the intensity of the reflected light beam. A magneto-optical recording and reproducing method characterized by: