JP2661532B2 - Method of manufacturing magneto-optical recording medium and magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium, and more particularly to an optical disk comprising MnBi which is used for a rewritable magneto-optical disk or the like and can read out a magneto-optical effect such as a magnetic Kerr effect or a magnetic Faraday effect. The present invention relates to a magnetic recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art The material of a magneto-optical recording medium mainly requires the following conditions. (A) A perpendicular magnetization film. (B) have a large coercive force; (C) The car rotation angle is large.

[0003] Heavy rare earth elements such as Tb, Gd, etc.
A 3d transition metal amorphous alloy thin film satisfies the above conditions, is suitable for mass production, and is considered to be promising because of its low readout noise. In particular, TbFeCb is promising and has become a practical material.

As a means for increasing the density of magneto-optical recording, there is a method of miniaturizing a recording area by narrowing a laser beam diameter. Objective lens N. of recording / reproducing head A. In order to narrow the beam diameter without changing the wavelength, it is necessary to shorten the wavelength of the laser light source. For this reason, development of a short wavelength light source using a non-linear optical element and the like has been advanced. However, it is known that a heavy rare earth-3d transition metal amorphous alloy film currently in practical use has a smaller Kerr rotation angle as the wavelength becomes shorter. Further, the quantum conversion efficiency of the photodetector also decreases due to the decrease in wavelength. Therefore, when reproduction is performed using a short-wavelength laser, the reproduction output is greatly reduced, and it is difficult to achieve a high recording density. Therefore, a new magneto-optical recording material having a large Kerr rotation angle in a short wavelength region is required.

[0005] Garnet, Pt / Co, and light rare earth-3d transition metal amorphous alloy films have been studied as magneto-optical recording materials for short wavelengths. However, these materials have the following disadvantages.

[0006] Garnet has a large Faraday rotation angle so that a large reproduction output can be obtained. However, in order to grow a crystal during or after film formation, heating at 600 ° C or higher is required, and a garnet must be heated on a normal glass substrate. It is difficult to create. Therefore, it is necessary to use heat-resistant glass as the substrate, and there is a disadvantage that the medium is expensive.

Pt / Co is heavy rare earth-3d in a short wavelength region.
It has a Kerr rotation angle larger than that of the transition metal amorphous alloy, but is not large enough to compensate for a decrease in the conversion efficiency of the photodetector. In addition, since it is crystalline, medium noise is large, and there is a disadvantage that the reproduction output in a short wavelength range is reduced (Japanese Patent Laid-Open No. Hei 3-162739).

In the case of the light rare earth-3d transition metal amorphous alloy thin film, similarly to the case of Pt / Co, there is a drawback that a sufficiently large Kerr rotation angle cannot be obtained in a composition range where recording and reproduction are possible.

Therefore, it is necessary to use a new material instead of these recording materials.

The MnBi compound is formed by heating and reacting a Mn—Bi laminated film in which Bi and Mn are sequentially formed on a substrate.
The C-axis orientation of Bi is preserved, resulting in a C-axis oriented MnBi compound. Since this MnBi compound has strong magnetic anisotropy in the C axis, it becomes a perpendicular magnetization film. Further, MnB
The i-compound is promising as a short-wavelength magneto-optical recording material because the Kerr rotation angle is as large as 1 degree or more from 400 nm to 900 nm.

Mn- is obtained by sequentially forming Bi and Mn on a substrate.
In order to heat the Bi laminated film and synthesize the compound, 3
It is necessary to hold the laminated film in an atmosphere at a temperature of 00 ° C. or higher (for example, in 1976, Journal of Applied Physics, 47, p. 3609 (J. Appl.
Phys. , 47 (1976) 3609). For this reason,
A glass substrate having high heat resistance is used as the substrate.
When a thin film is formed on a normal tempered glass substrate, a dielectric underlayer is used as a barrier layer in order to prevent MnBi from being altered by an alkali metal or the like from the glass substrate.

Next, a method of manufacturing a conventional MnBi magneto-optical recording medium and the recording medium will be described with reference to the drawings.

FIG. 8 is a sectional view showing the structure of a conventional MnBi magneto-optical recording medium before heat treatment. On a glass substrate 1, an underlayer (silicon nitride film formed by sputtering) 2 is formed to a thickness of 100 nm, and a Bi layer 3 is formed to a thickness of 20 nm by an ion cluster beam method.
The Mn layer 4 to a thickness of 10 by ion cluster beam method.
The thickness of the interference layer (SiN by sputtering) 5 is 3
Reflection layer (Al film by sputtering method) with a thickness of 00 nm
6 was sequentially formed into a film having a thickness of 20 nm. The film thickness ratio of Bi and Mn was determined from the value at which the Kerr rotation angle after the heat treatment was maximized. As a result of composition analysis by ICP, it has been confirmed from XPS measurement that the composition ratio of Mn: Bi is excessively close to 80 at%, and that excess Mn is in an oxide state. M
Since n is a substance that is very easily oxidized, the Mn layer contains a high concentration of Mn oxide, and the composition ratio becomes excessively Mn to compensate for this. At this time, the Mn film formation rate is set to 0.1.
05 nm / s, the degree of vacuum during film formation is 3 × 10 ⁻⁶ torr. The film formation speed of Bi is 0.1 nm / s, and the degree of vacuum during film formation is 3 × 10 ⁻⁷ torr. In order to form the SiN interference layer by sputtering, the vacuum is once released after forming the Bi / Mn layer. This disk is heated to 320 ° C, 250 ° C, 180 ° C
For 1 hour to react Mn and Bi.

FIG. 9 shows a conventional MnB after heat treatment for one hour.
3 is an X-ray diffraction pattern of Compound i by the θ-2θ method.
The heat treatment temperature is (a) 180 ° C, (b) 250 ° C,
(C) is 320 ° C. MnBi by heat treatment at 320 ° C
Diffraction from the C plane appears, indicating that MnBi has been synthesized. On the other hand, MnBi was not synthesized in the heat treatments (a) and (b) at 300 ° C. or lower.

[0015]

Since it is necessary to hold the Bi / Mn laminated film in an atmosphere of 300 ° C. or higher for synthesizing the MnBi compound, usable substrates are limited to glass substrates having high heat resistance. There is.

Further, in order to perform a heat treatment at 300 ° C. or more,
In order to record a groove or a preformat signal on a glass substrate, an inexpensive method using a photopolymer cannot be used, and the surface of the glass substrate must be directly etched, resulting in poor productivity and high cost of the substrate.

It is an object of the present invention to provide M
An object of the present invention is to provide a method for producing a magneto-optical recording medium at low cost by synthesizing an nBi compound, and a magneto-optical recording medium obtained by the method.

[0018]

SUMMARY OF THE INVENTION The magneto-optical recording medium of the present invention
Is a method of forming an underlayer made of a dielectric on a substrate,
A method for producing a magneto-optical recording medium, comprising sequentially forming a layer, an Mn layer, and an interference layer comprising a dielectric and synthesizing a MnBi compound by heat treatment, wherein the Mn oxide concentration in the MnBi layer is 20 a
t% or less, and the half width of the rocking curve of Bi (006) of the Bi layer is 3.5 ° or less. Further, the heat treatment is performed at 200 ° C. or lower. Furthermore, the magneto-optical recording medium of the present invention
Substrate made of dielectric, MnBi compound layer, dielectric
Of magneto-optical recording media with stacked interference layers
The Mn oxide concentration in the MnBi compound is 20 at
% Or less.

Further, as the substrate of the present invention, a glass substrate having a groove formed by photopolymer can be used.

[0020]

A glass substrate having a groove formed by a photopolymer is used as a substrate of a normal magneto-optical recording medium because it is inexpensive and has no birefringence. Since the decomposition temperature of the photopolymer is 210 ° C., in an atmosphere at a temperature of 200 ° C. or less, deterioration such as groove deformation does not occur, and a high-quality magneto-optical recording medium can be manufactured.

In order to synthesize an MnBi compound having a high Kerr rotation angle at 200 ° C. or less, the starting material B
The Mn oxide concentration of the Mn layer in the i / Mn laminated film must be 20% or less, and the half width of the rocking curve of the Bi (006) plane of the Bi layer must be 3.5 ° or less.

The reaction of Bi / Mn proceeds by diffusion of Mn atoms into Bi crystals. In order for the MnBi compound to exhibit magnetism, the MnBi microcrystals generated by diffusion must be MnBi microcrystals.
It is necessary to recrystallize while removing the oxide. This Mn
Elimination of the oxide concentration requires a higher temperature than the diffusion of Mn atoms. In order to reduce the synthesis temperature to 200 ° C. or lower, the Mn oxide concentration in the MnBi compound needs to be 20 at% or lower.

The diffusion rate of Mn atoms into the Bi crystal varies depending on the crystal orientation of the Bi layer. The higher the C-axis orientation of the Bi layer, the higher the diffusion rate. Synthetic temperature 200
° C or lower, Bi, which is an index of C-axis orientation, is used.
The half width of the rocking curve of the (006) plane needs to be 3.5 ° or less.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a MnBi magneto-optical recording medium and the recording medium will be described with reference to the drawings. FIG. 1 shows M
FIG. 3 is a cross-sectional view illustrating a configuration of an nBi magneto-optical recording medium before heat treatment.
Glass substrate 1 with grooves formed by photopolymer
An underlayer (silicon nitride film formed by sputtering) 2 is
The Bi layer 3 has a thickness of 20 nm by the ion cluster beam method, the Mn layer 4 has a thickness of 8 nm by the ion cluster beam method, and the interference layer (SiO by the ion cluster beam method) 5 has a thickness of 300 nm. A reflective layer (Al film by sputtering) 6 was sequentially formed to a thickness of 20 nm. The Mn film formation rate is 0.2 nm / s, and the degree of vacuum during the film formation is 1 × 10 ⁻⁶ torr. The film formation rate of Bi is 0.045 nm / s, and the degree of vacuum during film formation is 3.times.10@-7 ton.
rr. The Mn oxide concentration and the crystal orientation of Bi can be changed depending on the film forming conditions. Mn and Bi were reacted under various heat treatment conditions to synthesize a MnBi compound.

FIG. 2 shows Mn after heat treatment at 200 ° C. for 10 hours.
3 is an X-ray diffraction pattern of a Bi compound by a θ-2θ method. (A) has a Mn oxide concentration of 35 at%, and (b) has a Mn oxide concentration of 2 at%.
5 at% and (c) are 20 at%. The Mn oxide concentration was changed by the Mn film formation rate and the vacuum during the film formation.
The film formation rate in (a) is 0.04 nm / s, and the degree of vacuum during the film formation is 1 × 10 ⁻⁴ torr. The film formation rate of (b) is 0.
04 nm / s, and the degree of vacuum during film formation is 1 × 10 ⁻⁶ torr. The film formation speed of (c) is 0.2 nm / s, and the degree of vacuum during the film formation is 1 × 10 ⁻⁶ torr. Mn oxide concentration is 2
In (C) of 0 at%, MnBi (002) (004)
It can be seen that only diffraction from the surface exists, and a C-axis oriented MnBi film is obtained. In (b) of 25 at%,
Since the reaction is not completed, diffraction from Bi crystals is observed. M
In the case of (a) having the largest amount of n-oxide, growth of the MnBi phase is not observed.

FIG. 3 shows MnB after heat treatment at 200 ° C. for 1 hour.
3 is an X-ray diffraction pattern of Compound i by the θ-2θ method.
By shortening the heat treatment time, the influence of the Mn oxide becomes remarkable. (A) has a Mn oxide concentration of 25 at%, (b)
Is 21 at% and (c) is 20 at%. In (C) where the Mn oxide concentration is 20 at%, MnBi (002)
Only diffraction from the (004) plane exists, and C-axis oriented M
It can be seen that an nBi film has been obtained. In the case of (b) of 21 at%, diffraction from the Bi crystal is observed because the reaction is not completed. In (a) where the Mn oxide is the largest, MnBi
Little layer growth is seen. From the results of the above X-ray diffraction, it is understood that the Mn oxide concentration needs to be 20 at% or less in order to synthesize MnBi at a heat treatment temperature of 200 ° C. or less. Since the heat treatment temperature is proportional to the Mn oxide concentration, it is necessary to lower the Mn oxide concentration in order to further lower the heat treatment temperature.

Next, the influence of the crystal orientation of Bi will be described. FIG.
Are Bi of the three types of MnBi magneto-optical recording media before heat treatment.
It is a rocking curve of a (006) plane. The half width of the rocking curve is an index of the crystal orientation of the Bi layer, and the larger the half width, the lower the crystal orientation. The crystal orientation of Bi can be improved by reducing the film formation rate of Bi. In addition, the ionization lowers the C-axis orientation. The respective deposition rates are (a) and (b) 0.29 nm / s, and (c) is 0.045 nm / s. Only (a) is ionized. The respective half widths are (a) and (b) 0.29 nm / s, and (c) is 0.045 nm / s. Only (a) is ionized. Each half width is (a) 5.1 °,
(B) is 4.2 ° and (c) is 3.4 °. MnBi
The Mn oxide concentration of the layer is constant at 20 at%. FIG.
It is an X-ray diffraction pattern by the (theta) -2 (theta) method of the MnBi compound after heat processing at 200 degreeC for 1 hour. (A), (b),
(C) corresponds to FIG. In the case of Bi having a high C-axis orientation (c), only diffraction from the MnBi (002) (004) plane is present, and it can be seen that a M-axis oriented MnBi film is obtained. On the other hand, in (a) and (b), in which the C-axis orientation of Bi is low, diffraction from the Bi crystal is observed because the reaction is not completed.

FIG. 6 shows the half width of the rocking curve of the Bi (006) plane and the Bi (00) after heat treatment at 200 ° C. for 1 hour.
6) and the relationship between the relative intensities of MnBi (004).
200 ° C. by using Bi having a half width of 3.5 ° or less.
MnBi without unreacted Bi can be synthesized by the following heat treatment.

FIG. 7 shows Mn after heat treatment at 150 ° C. for 160 minutes.
3 is an X-ray diffraction pattern of a Bi compound by a θ-2θ method. By lowering the heat treatment temperature, the influence of Bi orientation becomes remarkable, and it can be seen that MnBi is generated only with high orientation (C).

A similar experiment was performed by heat treatment at 210 ° C.
The photopolymer forming the groove was deformed and could not be used as a magneto-optical recording medium.

[0031]

As described above, according to the present invention, Mn is obtained.
A magneto-optical recording medium using a Bi recording layer can be manufactured on a glass substrate on which a groove is formed with a photopolymer, and the present invention has an effect of providing a high-performance and inexpensive magneto-optical recording medium.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a magneto-optical recording medium according to the present invention before heat treatment.

FIG. 2 is a view showing an X-ray diffraction pattern of a MnBi compound after a heat treatment at 200 ° C. for 10 hours by a θ-2θ method.

FIG. 3 shows the θ of the MnBi compound after heat treatment at 200 ° C. for 1 hour.
It is a figure which shows the X-ray diffraction pattern by the 2 (theta) method.

FIG. 4 is a diagram showing rocking curves of a Bi (006) plane of three types of MnBi magneto-optical recording media before heat treatment.

FIG. 5 shows θ of MnBi compound after heat treatment at 200 ° C. for 1 hour.
It is a figure which shows the X-ray diffraction pattern by the 2 (theta) method.

FIG. 6 shows the half width of the rocking curve of Bi (006) plane and Bi (006) and MnBi after heat treatment at 200 ° C. for 1 hour.
It is a figure which shows the relationship of the relative intensity of (004).

FIG. 7 is a view showing an X-ray diffraction pattern of a MnBi compound after a heat treatment at 150 ° C. for 160 minutes by a θ-2θ method.

FIG. 8 is a partial cross-sectional view of a conventional magneto-optical recording medium before heat treatment.

FIG. 9 shows the θ of the conventional MnBi compound after heat treatment for 1 hour.
It is a figure which shows the X-ray diffraction pattern by the 2 (theta) method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 SiN underlayer 3 Bi layer 4 Mn layer 5 SiN protective layer 6 Al reflection film

Claims (4)

(57) [Claims] An underlayer made of a dielectric material on a substrate, Bi
A Mn layer, an Mn layer, and an interference layer composed of a dielectric material. The MnBi compound is synthesized by heat treatment.
at% or less and the heat treatment at 200 ° C. or less. 2. An underlayer made of a dielectric material on a substrate, Bi
A method of manufacturing a magneto-optical recording medium in which an MnBi compound is synthesized by heat treatment by sequentially forming an interference layer comprising a layer, a Mn layer, and a dielectric, wherein the half width of the rocking curve of the Bi (006) plane of the Bi layer is 3.5 ° or less;
Production of a magneto-optical recording medium characterized in that the temperature is not higher than 00 ° C.
Construction method . 3. An underlayer made of a dielectric, MnB, on a substrate.
In a magneto-optical recording medium having an i-compound layer and an interference layer formed of a dielectric layer, a Mn oxide concentration in the MnBi compound is 20 at% or less. 4. An underlayer made of a dielectric material on a substrate, MnB
i compound layer, in the magneto-optical recording medium in which the interference layer is laminated to a dielectric, wherein the substrate is characterized in that it is a glass substrate formed with grooves by photopolymer 請
The magneto-optical recording medium according to claim 3 .