JP3128232B2 - Magneto-optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium in which a rare earth-transition metal-based amorphous alloy film is supported as a magneto-optical recording film on a substrate, and more particularly to a rare earth element. -It relates to the composition of the transition metal based amorphous alloy film.

[Prior Art] Conventionally, as a magneto-optical recording film, a magneto-optical recording medium in which a rare earth-transition metal based amorphous alloy film is formed on one surface of a substrate has been known.

In the formation of the magneto-optical recording film, a film-forming material gasified in a vacuum or a low-pressure atmosphere, such as sputtering, ion plating, and vacuum deposition, is attached to the substrate surface and grown into a film. However, if the evacuation (vacuum evacuation) in the vacuum vessel before the start of film formation is insufficient, the film reacts with nitrogen and oxygen in the air remaining in the vacuum vessel to form a light. Active rare earths in the magnetic recording film are easily nitrided and oxidized, and if the reaction proceeds excessively, the Kerr rotation angle decreases and the output of the read signal decreases, or the perpendicular magnetic anisotropy energy decreases and the perpendicular magnetic anisotropy decreases. A phenomenon occurs in which recording cannot be performed.

Due to such inconvenience, nitrogen and oxygen mixed in the magneto-optical recording film have conventionally been recognized as impurities, and technical studies have been conducted in the direction of preventing nitrogen and oxygen from being mixed in the magneto-optical recording film. Has been done. As an example, to minimize the amount of air remaining in the vacuum vessel,
Although as much as possible evacuation be performed highly has been studied, since the higher the productivity for advanced vacuuming is deteriorated, and balanced against the recording / reproducing characteristics and productivity, for example, 10 ^{- A} method has been proposed in which evacuation is performed to the order of ⁵ [Pa].

[Problems to be Solved by the Invention] However, a rare earth-transition metal based amorphous alloy film produced by the above-described method and in which the mixing ratio of nitrogen or oxygen is adjusted to a low level is inversely perpendicular magnetic anisotropy. The energy becomes too high, and thus the domain wall energy becomes too high, so that a large external magnetic field (for example,
Coil) is required.

When a large external magnetic field is provided, (1) power consumption increases, (2) a space for setting the external magnetic field increases, and a recording / reproducing apparatus becomes large. Due to various inconveniences such as deterioration of the dynamic characteristics of the read / write head, a magneto-optical recording medium capable of recording and erasing information with a small external magnetic field has been demanded in designing a recording / reproducing apparatus.

The inventors of the present invention have a relationship between the mixing ratio of nitrogen and oxygen mixed into the rare earth-transition metal based amorphous alloy film and the residual Kerr rotation angle, a relationship between the mixing ratio and the perpendicular magnetic anisotropy constant,
As a result of studying the relationship between the mixing ratio and the C / N ratio,
We have learned that there is a region where only the perpendicular magnetic anisotropy energy can be reduced without reducing the Kerr rotation angle.

The present invention has been made based on the above-described findings, and has a high Kerr rotation angle by adjusting the mixing ratio of nitrogen and oxygen mixed in a rare earth-transition metal-based amorphous alloy film. It is another object of the present invention to provide a magneto-optical recording medium having a small perpendicular magnetic anisotropy energy.

Means for Solving the Problems In order to achieve the above object, the present invention firstly comprises a rare earth-transition metal based amorphous alloy to which chromium, titanium or niobium is added on a substrate. In a magneto-optical recording medium comprising a magneto-optical recording film and an inorganic dielectric film made of a nitride or oxide of silicon, aluminum, zirconium, titanium or tantalum, The alloy was configured to contain 0.1 to 5.0 [atomic%] of nitrogen and oxygen in total with respect to the alloy.

Second, a magneto-optical recording film made of a rare earth-transition metal based amorphous alloy to which chromium, titanium, or niobium is added, and a nitride of silicon, aluminum, zirconium, titanium, or tantalum or In a magneto-optical recording medium carrying an inorganic dielectric film made of an oxide, the magneto-optical recording film contains nitrogen and oxygen in a total amount of 0.1 to 5.0 [atomic%] with respect to the amorphous alloy. And
The saturation recording magnetic field and / or the erasing magnetic field of the magneto-optical recording medium is set to 200 [Oe] or less.

[Action] According to the study of the present inventors, nitrogen and oxygen are contained in the rare earth-transition metal based amorphous alloy film in an amount of 0.1 to 5.0 [atomic%].
When contained, only the perpendicular magnetic anisotropy energy can be reduced without reducing the Kerr rotation angle. Therefore, the external magnetic field can be reduced in size and weight, and power consumption can be reduced, the size of the recording / reproducing device can be reduced, and the speed of recording and erasing operations can be increased.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of a film structure of a magneto-optical recording medium according to the present invention, wherein a first multiple interference film 3 and a magneto-optical recording film are formed on a signal pattern forming surface 2 of a transparent substrate 1. 4 and
The second multiple interference film 5 and the thermal diffusion film 6 are sequentially laminated.

The transparent substrate 1 is formed of a plastic material such as polycarbonate, polymethyl methacrylate, polyolefin, or epoxy, or a transparent material such as glass into a desired shape such as a disk shape or a card shape.

A signal pattern such as a guide groove for guiding a recording / reproducing light beam spot and a bribit string representing a header signal is formed on the signal pattern surface 2 in a fine uneven shape. In FIG. 1, a signal pattern is directly formed on one surface of the transparent substrate 1. However, a photocurable resin layer having a refractive index similar to that of the transparent substrate is formed on one surface of the transparent substrate formed in a plate shape. And the signal pattern can be transferred to the surface of the photocurable resin layer.

The first multiple interference film 3 includes a magneto-optical recording film 4 and a transparent substrate 1.
Is provided in order to cause a reproduction light beam to cause multiple interference between them and increase an apparent Kerr rotation angle,
It is made of an inorganic dielectric material such as silicon, aluminum, zirconium, titanium, or tantalum nitride or oxide having a refractive index larger than that of the transparent substrate 1, and is formed to a thickness of 600 to 1000 °. As a means for forming the film 3, sputtering is particularly preferable.

The magneto-optical recording film 4 has a total amount of both nitrogen and oxygen in the film.
It is composed of a rare earth-transition metal based amorphous alloy film mixed with 0.1 to 5.0 [at%], and is formed to a thickness of 200 to 500 °. As the rare earth-transition metal based amorphous alloy film, rare earth (for example, terbium, gadolinium, neodymium, dysprosium). , Transition metals (eg, iron, cobalt, nickel) and additional elements (eg, chromium, titanium, niobium)
Particularly, a ternary alloy system containing

 The method of forming the magneto-optical recording film 4 will be described below.

(1) After forming the first multiple interference film 3, the rare earth
A transition metal-based amorphous alloy film is formed by an appropriate method, and then, before the second multiple interference film 5 is laminated on the rare earth-transition metal-based amorphous alloy film, the rare earth-transition metal System amorphous alloy film, the degree of vacuum is 1.0 × 10 ^{−5 to} 1.0 × 10 ⁻³ (Pa)
In a vacuum vessel adjusted to 5 to 90 minutes, 20 to 120
While maintaining the temperature at [° C.], the rare earth-transition metal based amorphous alloy film is nitrided or oxidized to obtain a desired magneto-optical recording film 4.

(2) After forming the first multiple interference film 3, the rare earth
A transition metal-based amorphous alloy film is formed in an atmosphere containing a mixed gas of nitrogen and oxygen at a partial pressure of 0.1 to 5.0 [%], and a rare earth-transition metal-based amorphous alloy film is formed in this film forming process. The desired magneto-optical recording film 4 is obtained by nitriding and oxidizing.

As a method for creating an atmosphere containing a mixed gas of nitrogen and oxygen at a partial pressure of 0.1 to 5.0% described in the above (2), the following method is available.

(A) After evacuating the vacuum container to a high degree of vacuum of the order of 10 ^-5 [Pa], a mixed gas of nitrogen and oxygen is supplied into the vacuum container, and nitrogen and oxygen in the vacuum container during the film forming process are supplied. Is adjusted to 0.1-5.0%.

(B) The degree of vacuum in the vacuum vessel is reduced to 1.0 × 10 5 by evacuation performed before the formation of the rare earth-transition metal amorphous alloy film.
^{-4 to} 5.0 × 10 ^-4 (Pa), and 0.1 to 5.0 in a vacuum vessel
[%] Partial pressure of air is left.

In addition, as a method of forming a rare earth-transition metal based amorphous alloy film, sputtering, ion plating,
Any vacuum film formation method such as vacuum evaporation can be applied.

The second multiple interference film 5 is made of the same inorganic dielectric as the first multiple interference film 3, and is formed to a thickness of 50 to 500 °. Regarding the forming method, the same method as that of the first multiple interference film 3 is used.

The thermal diffusion film 6 is made of a metal material such as gold, silver, steel, or aluminum, or an alloy obtained by adding an additional element such as titanium, nickel, or tantalum, and is formed to a thickness of 300 to 1000 mm. This thermal diffusion film 6 is formed by sputtering,
Ion plating, vacuum deposition, etc., can be formed by any vacuum film forming method, but in order to simplify the manufacturing process, it can be formed by the same vacuum film forming method as the films 3, 4, 5 described above. Particularly preferred.

FIG. 2 shows the relationship between the nitrogen mixing ratio and oxygen mixing ratio in the magneto-optical recording film 4 and the perpendicular magnetic anisotropy constant, and FIG. 3 shows the nitrogen mixing ratio and oxygen mixing ratio in the magneto-optical recording film 4. This shows the relationship with the remaining Kerr rotation angle.

As shown in FIG. 2, the perpendicular magnetic anisotropy constant Ku of the magneto-optical recording film decreases sensitively with the incorporation of nitrogen or oxygen, and gradually decreases as the incorporation rate of nitrogen or oxygen increases. When the mixing ratio of nitrogen or oxygen exceeds 5.0 [atomic%], the magnetic field becomes equal to or less than the demagnetizing field, and the magnetic moment tilts in the plane.

On the other hand, as shown in FIG. 3, the residual Kerr rotation angle is relatively stable against the mixing of nitrogen and oxygen, and the mixing rate is 0%.
In the range of -5.0 [atomic%], it hardly decreases. When the mixing ratio exceeds 5.0 [atomic%], the residual Kerr rotation angle sharply decreases, which is due to the disappearance of the perpendicular magnetic anisotropy shown in FIG. The degree of decrease in the residual Kerr rotation angle occurs more rapidly when the oxygen mixing rate is increased than when the nitrogen mixing rate is increased.

From FIGS. 2 and 3, it can be seen that by adjusting the nitrogen mixing ratio and oxygen mixing ratio in the magneto-optical recording film to 0 to 5.0 [atomic%], recording and erasing of information can be performed without lowering the signal output level. It can be understood that the external magnetic field required for (1) can be reduced.

FIGS. 5, 6, and 7 show the nitrogen mixing ratio and oxygen mixing ratio in the magneto-optical recording film 4, the C / N of the reproduction output signal, the saturation recording magnetic field, and the external magnetic field at which the erasure ratio becomes -40 dB. , Ie, the relationship with the erasing magnetic field. However, a disk-shaped magneto-optical recording medium having the film structure shown in FIG. 4 was used as a sample.

As shown in FIG. 5, in the relationship between the nitrogen mixing ratio and C / N, the C / N hardly changes even if the mixing ratio is changed within the range of 0 to 5.0 [at. ], The C / N gradually decreases when the amount exceeds 6.0 [atomic%]. On the other hand, in the relationship between the oxygen mixing ratio and C / N, even if the mixing ratio is changed in the range of 0 to 3.5 [at%], the C / N hardly changes, but from around 3.5 [at%]. C / N gradually decreases, and when it exceeds 5.5 [atomic%], C / N decreases rapidly.

As shown in FIG. 6, the erosion recording magnetic field, that is, the minimum magnetic field at which the carrier and the noise reach a level when a sufficiently large external magnetic field is applied, is obtained by changing the nitrogen mixing rate and the oxygen mixing rate. It shows the same tendency even when it is changed. The saturation recording magnetic field can be reduced by increasing the nitrogen mixing rate and the oxygen mixing rate. If nitrogen or oxygen of 0.1 atomic% or more is mixed, the saturation recording magnetic field can be reduced by 200 [Oe ] Can be as follows. At present, the target is to set the saturation recording magnetic field to 225 [Oe] or lower, as specified in the ISO standard. By setting the nitrogen mixing rate or oxygen mixing rate to 0.1 [at. You can clear your goals.

Also, as shown in FIG. 7, the nitrogen mixing rate of the erasing magnetic field (in this example, the erasing ratio, that is, the external magnetic field where the noise level after erasing was −40 dB with respect to the carrier level at the time of recording) was changed. The same tendency is exhibited in both cases where the oxygen concentration is changed and when the oxygen mixing ratio is changed. The erasing magnetic field can be lowered as the nitrogen mixing rate increases and the oxygen mixing rate increases. If nitrogen or oxygen of 0.1 atomic% or more is mixed, the erasing magnetic field can be reduced to 200 Oe or less. Can be

Thus, the data in FIGS. 5, 6 and 7 are
This corresponds to the data shown in FIGS.

Hereinafter, experimental examples and comparative examples of the present invention will be described, and the C / N, erosion recording magnetic field, erasing magnetic field, and nitrogen mixing rate and oxygen mixing rate in the magneto-optical recording film 4 of each example of the magneto-optical recording medium will be described. Show.

<Experimental example 1> After sputtering AlSiON to a thickness of 800 mm as a first multiple interference film on the signal pattern surface of a polycarbonate substrate, the inside of a vacuum vessel containing the substrate was 5x10.
^-5 [Pa], and then supply pure argon gas as a sputtering gas into the vacuum vessel to adjust the gas pressure in the vacuum vessel to a predetermined value.
The TbFeCo film was sputtered to a thickness of 250 mm.

After the formation of the TbFeCo film, the inside of the vacuum vessel was again filled with 5 × 10 ⁻⁵ [P
a), and the TbFeCo film was heated to 80 ° C. for 15 minutes in this.

After heating, a second multiple interference film is formed on this TbFeCo film.
AlSiON is sputtered to a thickness of 800 mm, and this A
On the lSiON film, AlCr was sputtered to a thickness of 750 mm as a thermal diffusion film to obtain a disk-shaped magneto-optical recording medium.

<Experimental Example 2> AlSiON was sputtered to a thickness of 800 mm as a first multiple interference film on the signal pattern surface of a polycarbonate substrate, and then the inside of a vacuum vessel containing the substrate was 2 × 10 4.
^-5 [Pa], and a gas mixture of 99 [at%] of argon and 1 [at%] of nitrogen is supplied as a sputtering gas into the vacuum vessel to adjust the gas pressure in the vacuum vessel to a predetermined value. The TbFeCo film was adjusted to 250 ガ ス under this gas pressure condition.
Was sputtered to a thickness of

Immediately after forming the TbFeCo film, without performing heat treatment,
A second multiple interference film and a heat diffusion film were formed on the TbFeCo film to obtain a disk-shaped magneto-optical recording medium. The composition, film thickness, and film forming method of the second multiple interference film and the thermal diffusion film are the same as those in Experimental Example 1.

<Experimental Example 3> After a sputtered AlSiON layer having a thickness of 800 mm was formed as a first multiple interference film on the signal pattern surface of a polycarbonate substrate, the inside of a vacuum vessel containing the substrate was 2 × 10 4.
^-4 (Pa), and then supply pure argon gas as a sputtering gas into the vacuum vessel to adjust the gas pressure in the vacuum vessel to a predetermined value.
The TbFeCo film was sputtered to a thickness of 250 mm.

After forming the TbFeCo film, the degree of vacuum in the vacuum vessel is reduced to 3 × 10 ^-4
５5 × 10 ⁻⁵ [Pa], and the TbFeCo film was 30
[Minute] Left. At this time, the temperature of the TbFeCo film is 40
[° C].

After the standing, a second multiple interference film and a heat diffusion film were formed on the TbFeCo film to obtain a disk-shaped magneto-optical recording medium. The composition, film thickness, and film forming method of the second multiple interference film and the thermal diffusion film are the same as those in Experimental Example 1.

<Experimental Example 4> After sputtering AlSiON to a thickness of 800 mm as a first multiple interference film on the signal pattern surface of a polycarbonate substrate, the inside of a vacuum vessel containing the substrate was 2 × 10 4.
^-5 [Pa] and then 99.5 [at.%] Of argon and 0.5
[Atomic%] gas mixture is supplied to adjust the gas pressure in the vacuum vessel to a predetermined value, and the TbFeCo film is formed under the gas pressure conditions.
Sputtered to a thickness of 250 mm.

Immediately after forming the TbFeCo film, without performing heat treatment,
A second multiple interference film and a heat diffusion film were formed on the TbFeCo film to obtain a disk-shaped magneto-optical recording medium. The composition, film thickness, and film forming method of the second multiple interference film and the thermal diffusion film are the same as those in Experimental Example 1.

<Experimental Example 5> AlSiON was sputtered to a thickness of 800 ° as a first multiple interference film on the signal pattern surface of a polycarbonate substrate, and then the inside of a vacuum vessel containing the substrate was 2 × 10 4.
^-5 [Pa] and then 99.5 [at.%] Of argon and 0.4
A gas mixture of [atomic%] and oxygen 0.1 [atomic%] was supplied to adjust the gas pressure in the vacuum vessel to a predetermined value. Under this gas pressure condition, a TbFeCo film was formed on the AlSiON film by 250 ° C. Sputtered to thickness.

Immediately after forming the TbFeCo film, without performing heat treatment,
On this TbFeCo film, a second multiple interference film and a heat diffusion film were sequentially laminated to obtain a disk-shaped magneto-optical recording medium. The composition, film thickness, and film forming method of the second multiple interference film and the thermal diffusion film are the same as those in Experimental Example 1.

<Comparative Example> After sputtering AlSiON to a thickness of 800 mm as a first multiple interference film on the signal pattern surface of a polycarbonate substrate, the inside of a vacuum vessel containing the substrate was 5x10.
^-5 [Pa], and then pure argon gas was supplied as a sputtering gas into the vacuum vessel to adjust the gas pressure in the vacuum vessel to a predetermined value. A TbFeCo film was sputtered to a thickness of 250 mm on the film.

Immediately after forming the TbFeCo film, without performing heat treatment,
On this TbFeCo film, a second multiple interference film and a heat diffusion film were sequentially laminated to obtain a disk-shaped magneto-optical recording medium. The composition, film thickness, and film forming method of the second multiple interference film and the thermal diffusion film are the same as those in Experimental Example 1.

FIG. 8 shows the outline of the method of manufacturing the magneto-optical recording medium according to each of the experimental examples and the comparative examples, the C / N, the saturation recording magnetic field, the erasing magnetic field, and the magneto-optical properties of the magneto-optical recording medium manufactured by each method. The nitrogen mixing rate and the oxygen mixing rate in the recording film 4 are shown.

As is clear from this figure, the magneto-optical recording media of Experimental Examples 1 to 5 have the same C / N of the reproduction output signal as the magneto-optical recording media of the comparative example (conventional example), but The recorded magnetic field is reduced to about 50% of the conventional example, and the erase magnetic field is reduced to 40% of the conventional example. Therefore, the external magnetic field required for recording and erasing information can be reduced in size and weight, and the magnet power supply unit can be simplified, the power consumption can be reduced, the recording / reproducing device can be downsized, and the recording and erasing operations can be performed. Higher speed can be achieved. Further, when viewed from the medium side, a large margin can be provided for the fluctuation in the distance between the external magnetic field and the magneto-optical recording medium and the fluctuation in the magnetic field due to heat generation, and a highly reliable magneto-optical recording medium can be obtained. .

In the above embodiment, a magneto-optical recording medium in which a first multiple interference film, a magneto-optical recording film, a second multiple interference film, and a heat diffusion film are laminated on a signal pattern surface of a substrate is taken as an example. However, the gist of the present invention is not limited to this, and the invention can be applied to a magneto-optical recording medium having an arbitrary film structure as long as it has at least a magneto-optical recording film.

[Effects of the Invention] As described above, the magneto-optical recording medium of the present invention has a magneto-optical recording film made of a rare earth-transition metal based amorphous alloy to which chromium, titanium, or niobium is added. ,
In a magneto-optical recording medium carrying an inorganic dielectric film made of silicon, aluminum, zirconium, titanium or tantalum nitride or oxide, the magneto-optical recording film contains a total amount of the amorphous alloy. Since the composition contains 0.1 to 5.0 [atomic%] of nitrogen and oxygen, it is possible to reduce the external magnetic field required for recording and erasing information without lowering the output level of the reproduction signal.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a principal part schematically showing an example of a film structure of a magneto-optical recording medium, FIG. 2 is a graph showing a relationship between a nitrogen mixing ratio and an oxygen mixing ratio and a perpendicular magnetic anisotropy constant, FIG. 3 is a graph showing the relationship between the nitrogen mixing ratio and oxygen mixing ratio and the residual Kerr rotation angle. FIG. 4 is a table showing an example of the composition and thickness of each film laminated on the magneto-optical recording medium. FIG. 5 is a graph showing the relationship between the nitrogen mixing ratio and oxygen mixing ratio measured using the magneto-optical recording medium of FIG. 4 and the C / N of the reproduced output signal, and FIG. 6 is the magneto-optical recording of FIG. FIG. 7 is a graph showing the relationship between the nitrogen mixing rate and oxygen mixing rate measured using the medium and the saturation recording magnetic field. FIG. 7 shows the nitrogen mixing rate and oxygen mixing rate measured using the magneto-optical recording medium of FIG. FIG. 8 is a graph showing a relationship with an erasing magnetic field, and FIG. 8 is a method for manufacturing a magneto-optical recording medium according to an experimental example and a comparative example. Is a table showing a C / N and saturated recording magnetic field and the erasing magnetic field and the nitrogen incorporation rate and oxygen mixture ratio. 1 ... transparent substrate, 2 ... signal pattern surface, 3 ... first multiple interference film, 4 ... magneto-optical recording film, 5 ... second multiple interference film, 6 ... thermal diffusion film.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoru Onuki 1-1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell Co., Ltd. (72) Noriyuki Ogihara 1-1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell (56) References JP-A-2-302949 (JP, A) JP-A-3-66048 (JP, A) JP-A-1-208749 (JP, A) JP-A-1-133240 (JP, A A) JP-A 1-311438 (JP, A) JP-A 62-132254 (JP, A) JP-A 61-87306 (JP, A) JP-A 61-84803 (JP, A) JP-A 61 -144743 (JP, A) JP-A-63-66746 (JP, A)

Claims (2)

(57) [Claims] 1. A magneto-optical recording film comprising a rare earth-transition metal based amorphous alloy to which chromium, titanium or niobium is added, and a nitride or oxide of silicon, aluminum, zirconium, titanium or tantalum on a substrate. In the magneto-optical recording medium carrying an inorganic dielectric film made of a material, the magneto-optical recording film contained nitrogen and oxygen in a total amount of 0.1 to 5.0 [atomic%] with respect to the amorphous alloy. A magneto-optical recording medium characterized by the above-mentioned. 2. A magneto-optical recording film comprising a rare earth-transition metal based amorphous alloy to which chromium, titanium or niobium is added, and a nitride or oxide of silicon, aluminum, zirconium, titanium or tantalum on a substrate. In a magneto-optical recording medium carrying an inorganic dielectric film made of a material, the magneto-optical recording film contains nitrogen and oxygen in a total amount of 0.1 to 5.0 [atomic%] with respect to the amorphous alloy. A magneto-optical recording medium, wherein a saturation recording magnetic field and / or an erasing magnetic field of the magneto-optical recording medium is set to 200 [Oe] or less.