JPH05234160A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To provide the overwritable magneto-optical recording medium with which high C/N is obtainable even if recording is executed by a short- wavelength laser. CONSTITUTION:The magneto-optical recording medium which executes magneto- optical recording, reproducing and erasing of information by using the laser beam and can be overwritten by using a preceding auxiliary magnetic field has the constitution consisting of a substrate 7/optical interference layer 6/MnBi layer 5/TbFe layer or TbFeCo layer 4/control layer 3/auxiliary recording layer 2/optical interference layer 1. The medium is so constituted that the film thickness of the MnBi layer 5 is smaller than the film thickness of the TbFe layer or TbFeCo layer 4. The overwritable exchange bond medium with which C/N of a high level is obtainable is produced even if reproducing is executed by the short-wavelength laser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overwritable magneto-optical recording medium.

[0002]

2. Description of the Related Art In recent years, a magneto-optical recording system that enables overwriting of information by using an initial auxiliary magnetic field and a magnetic multilayer film has been receiving attention. This system uses (a) a multilayer magneto-optical recording medium having a first layer having perpendicular anisotropy as a recording / reproducing layer and a second layer having vertical anisotropy as a recording auxiliary layer as (a) a recording medium. (B) moving the recording medium, and (c) applying only an initial auxiliary magnetic field so that only the magnetization of the auxiliary recording layer is aligned upward or downward before recording, (d) ) Irradiating the recording medium with a laser beam, (e) modulating the intensity of the laser beam on a pulse according to the binary information to be recorded, and (f) applying a recording magnetic field to the recording medium portion irradiated with the laser beam. (G) When the intensity of the pulse-modulated laser beam is at a high level, one of the bits having the upward magnetization and the bit having the downward magnetization is formed, and the intensity of the beam is at a low level. Sometimes possible to form the other beam, which is over-writable recording method comprising (e.g., JP 62-1759
48). A method has also been proposed in which a control layer is provided between the recording layer and the recording auxiliary layer to control the exchange coupling between the recording layer and the recording auxiliary layer.

On the other hand, although not a medium that can be overwritten, a medium using a MnBi-based material has also been proposed.

[0004]

In the prior art, only the medium using the transition metal in the recording layer was used. However, when the transition metal is used in the reproducing layer as described above, recording is performed with a laser having a short wavelength. In this case, since the Kerr rotation angle was small, the C / N obtained when recording and reproducing was limited.

An object of the present invention is to provide a medium in which MnBi and TbFe or TbFeCo are exchange-coupled with each other as a recording layer so that a high C / N ratio can be obtained even when recording with a short wavelength laser.
Another object of the present invention is to provide an overwritable magneto-optical recording medium.

[0006]

SUMMARY OF THE INVENTION The present invention is a magneto-optical recording medium for recording, reproducing and erasing information by using a laser beam, in which a medium which can be overwritten by using a preceding auxiliary magnetic field is a substrate. / Optical interference layer / MnBi layer / T
bFe layer or TbFeCo layer / control layer / recording auxiliary layer /
It is characterized by having a structure called an optical interference layer.

Further, according to the present invention, the thickness of the MnBi layer is TbF.
It is characterized in that it is thinner than the film thickness of the e layer or the TbFeCo layer.

[0008]

The function of MnBi is that the Kerr rotation angle is large even for a short wavelength laser. Further, since TbFe or TbFeCo has a large coercive force at room temperature, it is easy to write a stable recording bit, and since the Curie temperature is low, the magnetization information can be transferred from the recording auxiliary layer with a relatively low level laser power. Is. Therefore, by producing an overwrite exchange coupling medium using an exchange coupling two-layer film composed of MnBi and TbFe as a recording layer, it is possible to transfer the magnetization information from the recording auxiliary layer to the recording layer with a low level laser power, and It becomes a medium which can obtain a high C / N even when reproduced by a laser having a short wavelength.

[0009]

FIG. 1 is a schematic view of a magneto-optical recording two-layer film medium showing an example of the present invention. The medium structure is as follows: substrate 7 / optical interference layer 6 / MnBi layer 5 / TbFe or TbFeCo layer 4 /
Control layer 3 / recording auxiliary layer 2 / optical interference layer 1. Here, as the substrate 7, a substrate made of polycarbonate resin, epoxy resin, or glass is used. It may be one in which a groove is formed on the glass with an ultraviolet curable resin or the like. As the optical interference layers 6 and 1, silicon nitride,
Silicon oxide, tantalum oxide, aluminum nitride, aluminum oxide, etc. can be used. As the recording auxiliary layer 2 and the control layer 3, one or several kinds of rare earth metals such as Tb, Gd, Nd, Ho and Dy, and Fe, Co and Ni are used.
One kind or a combination of several kinds of transition metals can be used. A specific example is shown below.

Example 1 Polycarbonate (with groove) substrate / SiN (80 nm) / MnBi (10n)
m) / TbFe alloy (20 nm) / GdFe (5 nm)
/ GdTbFeCo (60 nm) / SiN (80 nm)
A medium having a film structure was produced. The film formation is all performed by continuous sputtering with an RF magnetron sputtering device.

With respect to the above medium, the recording wavelength is 680 nm, the linear velocity is 11.3 m / s, the recording frequency is 3.7 MHz, and the Dut is
Under the conditions of y ratio of 50%, recording magnetic field of 350 Oe, low laser beam power of 3 mW, and high level laser power of 11 mW, the same track was overwritten 10 times and reproduced, and C / N of 60 dB was obtained. Error rate is 10 ^-6
It was below.

(Example 2) Polycarbonate (with groove) substrate / SiN (74 nm) / MnBi (15n)
m) / TbFe alloy (10 nm) / GdNdFeCo
(3.5 nm) / GdDyTbFeCo (80 nm) /
A medium having a film structure of SiN (80 nm) was produced. The film formation is all performed by continuous sputtering with an RF magnetron sputtering device.

With respect to the above medium, the recording wavelength is 680 nm, the linear velocity is 11.3 m / s, the recording frequency is 3.7 MHz, and the Dut is
Under the conditions of y ratio of 50%, recording magnetic field of 300 Oe, low laser beam power of 3 mW, and high level laser power of 10 mW, the same track was overwritten 10 times and reproduced, and C / N 59 dB was obtained. Error rate is 10 ^-6
It was below.

(Example 3) Polycarbonate (with groove) substrate / SiN (74 nm) / MnBi (15n)
m) / TbFe alloy (20 nm) / NdFeCo (4.
0 nm) / GdDyFeCo (50 nm) / SiN (8
A medium having a film structure of 0 nm) was produced. The film formation is all performed by continuous sputtering with an RF magnetron sputtering device.

With respect to the above medium, recording wavelength 415 nm, linear velocity 11.3 m / s, recording frequency 3.7 MHz, Dut
Under the conditions of y ratio of 50%, recording magnetic field of 400 Oe, low laser beam power of 3 mW, and high level laser power of 10 mW, the same track was overwritten 10 times and reproduced, and C / N 54 dB was obtained. Error rate is 10 ^-6
It was below.

Example 4 Glass (with groove) substrate / ZnS (60 nm) / MnBi (20 nm) TbFe
Alloy (20nm) / GdFeCo (10nm) / GdF
A medium having a film structure of eCo (60 nm) / SiN (80 nm) was produced. The film formation is all performed by continuous sputtering with an RF magnetron sputtering device.

With respect to the above medium, recording wavelength 415 nm, linear velocity 11.3 m / s, recording frequency 3.7 MHz, Dut
Under the conditions of y ratio of 50%, recording magnetic field of 300 Oe, low laser beam power of 3 mW, and high level laser power of 12 mW, the same track was overwritten 10 times and reproduced, and C / N 56 dB was obtained. Error rate is 10 ^-6
It was below.

Example 5 Glass (with groove) substrate / ZnS (60 nm) / MnBi (20 nm) TbFe
Co alloy (20 nm) / GdFeCo (10 nm) / G
A medium having a film structure of dFeCo (60 nm) / SiN (80 nm) was produced. The film formation is all performed by continuous sputtering with an RF magnetron sputtering device.

With respect to the above medium, recording wavelength 415 nm, linear velocity 11.3 m / s, recording frequency 3.7 MHz, Dut
Under the conditions of y ratio of 50%, recording magnetic field of 350 Oe, low laser beam power of 3 mW, and high level laser power of 13 mW, the same track was overwritten 10 times and reproduced, and C / N 62 dB was obtained. Error rate is 10 ^-6
It was below.

[0020]

According to the present invention, it is possible to manufacture an overwritable exchange-coupling medium that can obtain a high level of C / N even when reproduced by a laser having a short wavelength.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a magneto-optical recording medium of the present invention.

[Explanation of symbols]

 1 Optical Interference Layer 2 Recording Auxiliary Layer 3 Control Layer 4 TbFe or TbFeCo Layer 5 MnBi Layer 6 Optical Interference Layer 7 Substrate

Claims (2)

[Claims] 1. In a magneto-optical recording medium for recording, reproducing and erasing information by using a laser beam, a medium which can be overwritten by using a preceding auxiliary magnetic field is a substrate / optical interference layer / MnBi layer / TbFe layer or TbFeCo
A magneto-optical recording medium having a structure of layer / control layer / recording auxiliary layer / optical interference layer. 2. The thickness of the MnBi layer is TbFe layer or Tb.
2. The FeCo layer is thinner than the film thickness of the FeCo layer.
The magneto-optical recording medium described.