JP2829321B2 - 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 recording and
More specifically, the present invention relates to a specific metal nitride magnetic thin film which has good perpendicular magnetic anisotropy and has a large Faraday rotation angle and is suitable for magneto-optical recording. .

[0002]

2. Description of the Related Art A magnetic thin film is applied to a suitable substrate (non-magnetic support).
The one formed above is used as a recording medium (magnetic recording medium, magneto-optical recording medium). In particular, the recording medium employed in the magneto-optical recording method (hereinafter referred to as the "magneto-optical recording medium") has a high recording sensitivity, a large magneto-optical effect (Faraday effect, Kerr effect), and a large area. It is required that the product can be manufactured homogeneously and inexpensively, and that it has excellent stability. In addition, the magnitude of the magneto-optical effect is greatest when the direction of magnetization is parallel to the direction in which light travels, and the condition of magnetization perpendicular to the plane also satisfies the requirements for perpendicular magnetic recording. Also suitable for density recording. Therefore, a material having magnetization perpendicular to the plane of the medium must be selected.

[0003] From such demands, as a magnetic material of a magneto-optical recording medium, (1) a magnetic material employed in a perpendicular magnetic recording medium (typically, a magnetoplumbite-type Ba ferrite having a hexagonal close-packed (hcp) structure); )
(2) MnBi, MnCuBi, MnGaGe, MnA
lGe, PtCo (polycrystalline above), (YBi) ₃ (Fe
Ga) ₅ O ₁₂ (single crystal), GdCo, GdFe, TbF
e, GdTbFe, TbDyFe (above amorphous)
Are used.

However, it is difficult to form the Ba ferrite magnetic material (1) at a low substrate temperature, and the wavelength range of a semiconductor laser (for example, 780 nm or 830 nm).
However, there is a disadvantage that a large magneto-optical effect cannot be obtained. However, attempts have been made to increase the Faraday effect by replacing, for example, trivalent iron ions with divalent Co and tetravalent Ti, but in this case, the film forming temperature is further increased, and the selection of the substrate material is increased. Will be greatly restricted. This tendency can be similarly applied to other oxide magnetic thin films such as garnet thin films.

On the other hand, in the magneto-optical recording medium using the polycrystalline material of the above (2), noise of light scattering due to grain boundaries becomes a problem, and a high S / N ratio cannot be obtained. Compared to the polycrystalline material, the magneto-optical recording medium using the amorphous material of the above (2) does not cause such inconveniences, and thus forms the mainstream of the magneto-optical recording medium. Has the disadvantage of being uneasy.

[0006] As a result of the progress of the development of magnetic materials having excellent stability without oxidization, the iron nitride has recently attracted attention.
This iron nitride does not rust, is a ferromagnetic material, and has magnetic anisotropy in the direction perpendicular to the substrate. Therefore, high-density magnetic recording media such as recording tapes, video tapes, and large-capacity storage devices for computers. (JP-A-55-33093 and JP-A-59-2287).
No. 05, No. 60-76021, No. 61-110328
And JP-A-62-103821.

However, the nitride magnetic materials proposed so far are mainly for perpendicular magnetic recording media focusing on perpendicular magnetic anisotropy, and their application to magneto-optical recording media has been postponed. That is the fact.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical recording medium capable of performing high-density recording and reproduction. Another object of the present invention is to provide a magneto-optical recording medium having improved reproduction efficiency particularly by the Faraday effect.

[0009]

According to the present invention, in order to solve the above-mentioned problems, at least one kind of a nitride of a metal selected from Co, Fe and Ni is provided on a non-magnetic support. A magneto-optical recording medium is provided, wherein a thin magnetic layer having perpendicular magnetic anisotropy containing the metal oxide is formed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magneto-optical recording medium of the present invention will be described below in detail. The magneto-optical recording medium of the present invention has a perpendicular magnetic anisotropy comprising, as a main component, a nitride of at least one metal selected from Co, Fe and Ni on a non-magnetic support, and further containing an oxide of the metal. Characterized in that a magnetic thin layer having the following characteristics is formed. In this magneto-optical recording medium, the amount of metal oxide in the magnetic thin film is preferably about 20% by weight or less.

In the magneto-optical recording medium, a reflective layer may be provided between the magnetic thin film and the non-magnetic support, or an amorphous rare earth / transition element alloy may be used instead of the reflective layer. A thin film can also be formed.

In this magneto-optical recording medium, it is also preferable that the magnetic thin film contains a fluoride of a metal selected from the group consisting of Fe, Co and Ni (in this case, the magnetic thin film of metal fluoride is preferred). Preferably, the amount thereof is about 40% by weight or less.

In this magneto-optical recording medium, it is preferable that the magnetic thin film contains an amorphous metal of any one of Fe, Co and Ni (in this case, the amorphous magnetic thin film of the metal is preferable). Preferably, the amount thereof is about 40% by weight or less.

Further, in this magneto-optical recording medium, the magnetic thin film may have the following ratio: 50 atomic% ≦ Fe, Co and / or Ni ≦ 80.
Atomic% 10 atomic% ≦ N ≦ 40 atomic% 2 atomic% ≦ C ≦ 45 atomic% 2 atomic% ≦ O ≦ 25 atomic% and containing carbon and oxygen are also preferable.

The method for producing a magneto-optical recording medium according to the present invention is characterized in that at least one type of metal atom selected from Fe, Co and Ni is provided directly on a nonmagnetic support or via a reflective layer or an amorphous rare earth / transition element alloy thin film. And nitrogen atoms are reacted and deposited in a magnetic field to form a metal nitride [M _x N (x = 2 to
3)] is characterized by forming a magnetic thin film having as a main component.

In this method of manufacturing a magneto-optical recording medium, a metal fluoride can be contained in the magnetic thin film by reacting a fluorine atom together with a nitrogen atom in a magnetic field.

In the method for manufacturing a magneto-optical recording medium, at least one selected from Fe, Co and Ni is used.
It is also preferable that a target is a kind of metal atom, an alloy thereof, a nitride and / or a fluoride thereof, and the target is bombarded with nitrogen which is made into plasma.

In the method of manufacturing a magneto-optical recording medium, it is also preferable that plasma-converted argon is used together with the plasma-converted nitrogen.

In the method for manufacturing a magneto-optical recording medium, carbon and oxygen atoms are reacted in a magnetic field together with the metal atoms (Fe, Ni, Co) and nitrogen atoms to thereby remove carbon and oxygen from the magnetic thin film. It is also preferable to make it contained.

In the method of manufacturing a magneto-optical recording medium, at least one metal selected from Fe, Co and Ni, an alloy thereof, a nitride and / or a fluoride thereof is used as a target, and plasma is applied to the target. It is also preferable to make the magnetic thin film contain carbon and oxygen by colliding nitrogen, carbon, and oxygen (in this case, the plasma-formed nitrogen, carbon, and oxygen are combined with argon to form a plasma). It is preferable to use).

Furthermore, in this method of manufacturing a magneto-optical recording medium, the magnetic field is mainly composed of a magnetic flux which is directed perpendicular to the surface of the non-magnetic support by a magnet disposed on the back side of the non-magnetic support. It is also preferable to use

Incidentally, the present invention has been studied and studied from various angles with respect to the iron nitride magnetic material. As a result, by forming Fe nitride using various film forming methods, particularly ion beam sputtering, it is possible to obtain a large perpendicular magnetic difference. Isotropic magnetic field ( _HA
≧ 4 KOe) and a magnetic thin film having excellent C-axis orientation and a Fadeler rotation angle (θ _FR ) of 0.3 deg / μm or more could be formed. In particular, it has been found that by improving the C-axis orientation, the translucency and the Faraday rotation angle are improved, which is suitable for a magneto-optical recording medium. Further, such a magnetic thin film is made of another iron group element (C
o, Ni) and Fe, Ni, Co
It was confirmed that it was also observed in nitrides containing two or more of the following.
The present invention has been made based on these.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. 1 and 2 show two typical examples of a magneto-optical recording medium according to the present invention.
1 is a non-magnetic support, 12 is a magnetic thin film, and 13 is a reflective layer.

A magneto-optical recording medium of the type shown in FIG.
The recording / reproducing laser beam is irradiated from the nonmagnetic support 11 side, and therefore, the nonmagnetic support 11 here must be transparent to light. On the other hand, in the magneto-optical recording medium of the type shown in FIG. 2, the recording / reproducing laser beam is irradiated from the side of the magnetic thin film 12, so that the non-magnetic support 11 here is transparent to light. Or opaque.

In these magneto-optical recording media,
If necessary, a protective layer or a lubricating layer may be provided on the reflective layer 13 forming the surface layer (in the case of FIG. 1) or on the magnetic thin film 12 (in the case of FIG. 2). Even if a dielectric layer for enhancing the magneto-optical effect is provided between the non-magnetic support 11 and the magnetic thin film 12 or between the magnetic thin film 12 and the reflective layer 13 in the example of FIG. Good.

As the nonmagnetic support 11, an appropriate nonmagnetic material such as a plastic film, ceramic, metal, or glass is used. As the plastic for the support 11, not only heat-resistant plastics such as polyimide, polyamide and polyethersulfone but also plastics such as polyethylene terephthalate, polyvinyl chloride, cellulose triacetate, polycarbonate and polymethyl methacrylate can be used. The support 11 may have any shape such as a sheet, a card, a disk, a drum, and a long tape.

The magnetic thin film 12 is represented by the general formula M _x N (where M is at least one kind of metal selected from Fe, Co and Ni, and x = 2 to 3). The main component is a nitride magnetic material having specific properties as described in (1). These nitride magnetic materials have a Curie point roughly determined by the value of x. Also, depending on the value of x, for example, if F _x N, bcc, f
It has a crystal structure such as cc, hcp, orth. The physical properties such as the magnetic properties also differ depending on these crystal structures. Among the crystal structures, f is useful as a recording medium (magnetic recording medium, magneto-optical recording medium).
Those having a cc structure and a hcp structure (ε phase) —especially those having an hcp structure (ε phase) are desirable—therefore, the M _x N magnetic thin film of the present invention is ε-M _x N and the vertical magnetic film is C
It is a polycrystalline thin film oriented in the axial direction.

As mentioned above, conventionally, M _x
When the N magnetic thin film is formed of polycrystal, unlike the amorphous magnetic thin film, there is a grain boundary, which causes noise at the time of light transmission and low light transmittance (10 to 2).
0%) It was considered that the Faraday rotation angle (θ _FR ) could not be large. However, according to the magnetic thin film of the present invention, such a concern does not become a problem, and it becomes possible to improve the repetition stability and the θ _FR value for photothermal writing, which is of practical interest.

According to observations made by the present inventors, the particle diameter of a polycrystal is several tens of degrees (about 50 degrees in Fe _x N).
Is small, has little effect on the wavelength of light, and has a large θ _FR value (about 0.7 deg / μ in Fe _x N).
m) Therefore, it was found that the S / N ratio can be increased.

Further, the present inventor has proposed that N (nitrogen) be replaced by Fe
If a large amount is contained in (iron), the laser light transmittance is improved and 4
It has been confirmed that it reaches as high as 0% (when λ = 800 nm). In the case of photothermal recording (Curie point recording), the magnetic thin film must absorb light to some extent and be used for heating.

The higher the N content in the iron nitride, the higher the light transmittance, but the magnetic thin film has a Curie temperature (T
c) Since heating must be performed close to this point, the Tc value is lower at this point (however, if the Tc value is lower than 50 ° C., it will hinder recording maintenance, so the limit is about 50 ° C.). The sensitivity is good. The value of x in Fe _x N should be brought close to 2-in other words, N
The Curie point (Tc) decreases as you add more. For practical use, Tc is desirably in the range of 100 to 200 ° C., but in the case of Fe ₃ N, Tc ℃ 290 ° C., which is the upper limit of the value of x. In the case of a nitride magnetic thin film, writing can be performed by utilizing a decrease in coercive force due to heating.

Although the conventional film made of iron nitride is called a perpendicular magnetization film, the perpendicular magnetic anisotropy is not always good. The magnetic thin film is not sufficient for perpendicular magnetic anisotropy not suitable bit diameter below the high density recording 1 [mu] m, perpendicular magnetic anisotropy field (H _A) is as small as 1 KOe, it now is to increase the theta _FR value Can not.

After all, the magnetic thin film of the present invention uses iron nitride Fe _x N (x is 2-3) as a magnetic material, the Faraday rotation angle is 0.3 deg / μm or more, and hc
It has a p-structure, is C-axis oriented (crystals are deposited in the C-axis direction), and has a perpendicular magnetic anisotropic magnetic field ( _HA ) of 4 KOe or more, preferably 5 KOe or more (generally, (About 6 to 7 KOe).

Such large values for the perpendicular magnetic anisotropy magnetic field (H _A ) and Faraday rotation angle (θ _FR ) are obtained because the Fe _x N magnetic thin film contains Fe ₄ N, α-Fe, etc. And the hexagonal ε-phase Fe _x N (2
This is because <x ≦ 3) is C-axis oriented. The present inventor has found that the light transmittance is improved according to the degree of C-axis orientation and that θ _FR −
It has been confirmed that the squareness ratio is improved in the H curve.
The degree of C-axis orientation can be evaluated using the half width (Δθ ₅₀ ) obtained from the rocking curve of the C plane in the X-ray diffraction method.
According to the present invention, Δθ ₅₀ obtained from (002) is 1 degree or less, and when it is 1 degree or more, the perpendicular anisotropic magnetic field becomes 5 KOe or less, and the light transmittance and the Faraday rotation angle are insufficient. Have also confirmed. As mentioned above, the ion beam sputtering method is particularly suitable for forming such a magnetic thin film.

Japanese Patent Application Laid-Open No. 61-20078 describes a magnetic material composed of ε-phase iron nitride Fe _x N (x = 2 to 3). This Fe _x N is a magnetic powder. In order to form the magnetic layer on the support, it is necessary to apply a binder or the like. Therefore, the sensitivity of the magnetic layer tends to be low, and recording is insufficient with the light heat of a semiconductor laser or the like. -Hc) is considered to be limited to the case where thermal transfer is performed by overlapping with -Hc).

JP-A-60-25204 describes a magnetic recording medium having a magnetic layer mainly composed of amorphous iron nitride Fe _1-x N _x (X ≧ 0.4).
-Iron nitride (amorphous iron nitride) and x ≧ 0.4
And many N components—outside the scope of the present invention—cannot achieve what is intended by the present invention (polycrystalline thin film).

Japanese Patent Application Laid-Open No. 62-232101 describes a method for producing an iron nitride magnetic material, and also describes C-axis orientation and perpendicular magnetic anisotropy. However, the iron nitride here has a perpendicular magnetic anisotropy magnetic field as low as about 1 KOe as shown in FIG.

The iron nitride forming the magnetic thin film according to the present invention has a perpendicular magnetic anisotropic magnetic field of about 4 KOe or more, preferably about 5 KOe or more (usually about 6 to 7 KOe or more).
It is what becomes.

The magnetic thin film of the present invention is not limited to a thin film made of iron nitride. In the above formula (M _× N), M is C
o, Ni or a combination of at least two kinds selected from Fe, Co and Ni may be used. However, also in these, x = 2 to 3 mentioned above, θ _FR is 0.3d
eg / μm or more, hcp structure, C-axis orientation, and perpendicular magnetic anisotropy magnetic field ( _HA ) are 4 KOe or more, preferably 5 KOe or more.
Needless to say, the condition above e must be satisfied.

The thickness of the magnetic thin film 12 is 0.05 to 0.5
μm, preferably about 0.05 to 0.2 μm is appropriate. In the magnetic thin film 12 of the present invention, since the perpendicular component of the nitride magnetic material is greatly increased, a large Faraday rotation angle can be obtained even with a thin film.

The material of the reflection layer 13 is Au, Al,
Ag, Pt, Cr, Nd, Ge, Rh, Cu, TiN, etc. are used, and various vapor deposition methods such as an electron beam (EB) vapor deposition method, ion plating, sputtering, PVD
It is formed by a thin film forming method such as a CVD method or a CVD method. The thickness of the reflective layer 13 is 1 μm or less, preferably 0.05 to 0.5 μm.
Is appropriate.

The material of the dielectric layer is SiO 2
₂ , TiO ₂ , silicon nitride, aluminum nitride, amorphous Si, etc., and the material of the lubricating layer is carbon, molybdenum dioxide, tungsten disulfide, α-olefin polymer, unsaturated hydrocarbon which is liquid at ordinary temperature ( Compounds in which an n-olefin double bond is bonded to a terminal carbon; about 20 carbon atoms, and fatty acid esters comprising a monobasic fatty acid having 12 to 20 carbon atoms and a monohydric alcohol having 3 to 12 carbon atoms. be able to.

Since the nitride magnetic material of the present invention becomes a good C-axis alignment film from the beginning of film formation without providing an underlayer, a C-axis alignment film can be obtained even at a thickness of 0.1 μm or less, for example, 0.05 μm. Therefore, a perpendicular magnetic anisotropic film having good transparency can be obtained. It is described that a perpendicular magnetic recording medium described in JP-A-59-228705 is difficult to obtain a perpendicular magnetic anisotropic film below 0.1 μm. For this reason, the portion having a thickness of 0.1 μm in the initial stage of film formation is inferior in translucency and perpendicular magnetic anisotropy, and cannot be said to be preferable for a magneto-optical recording medium which transmits and uses light in the entire film. This is clearly different from the above. Accordingly, the nitride magnetic body of the present invention does not require an underlayer, but may be provided. Its thickness is 0.05
About 0.5 μm is appropriate.

The position where the underlayer is provided is between the non-magnetic support 11 and the magnetic thin film 12 in the case of the magneto-optical recording medium shown in FIG.
If a dielectric layer is provided between the magnetic thin film 12 and the dielectric layer. In the case of the magneto-optical recording medium shown in FIG. 2, it is between the reflective layer 13 and the magnetic thin film 12.

The underlayer is selected from non-magnetic materials having a crystal plane whose lattice constant is the same as or close to that of the nitride magnetic thin film 12 formed thereon. Therefore, a vertical alignment film having an hcp structure grows on the nitride magnetic thin film 12 formed on the underlayer. As such an underlayer, it is particularly preferable to use a layer having an hcp structure such as Ti, Zr, or Mg.

In order to further improve the perpendicular magnetic anisotropy of the magnetic thin film 12, a non-magnetic element such as B, Si, P or the like is added to the magnetic thin film in an amount of 20% by weight or less. It is also effective to further improve the perpendicular magnetic anisotropy by lowering the saturation magnetization Ms. Also,
In order to further improve the Faraday rotation angle θ _FR of the magnetic thin film 12, it is also effective that paramagnetic ions such as Eu ²⁺ , Pr ³⁺ , and Tb ³⁺ are added to the magnetic thin film 12 and the underlayer. It is.

As means for reducing the saturation magnetization of the magnetic thin film 12 and improving the perpendicular magnetic anisotropy, it is effective to add oxygen to the magnetic thin film in addition to providing the underlayer.

Putting oxygen into the magnetic thin film 12 is as follows.
As a result, an oxide of Co, Ni and / or Fe (oxide magnetic material) is mixed with a nitride of Co, Ni and / or Fe.
Will coexist. Preferred specific examples of the oxide magnetic material of Co, Ni and / or Fe include FeO,
Fe ₂ O ₃ , Fe ₃ O ₄ , CoO, Co ₂ O ₃ , Co ₃ O ₄ , N
iO, Ni ₂ O _{3 and the} like. Each of these oxide magnetic materials is chemically and thermally stable, similarly to the nitride magnetic material. These oxide magnetic materials and nitride magnetic materials are mixed
When the coexisting nitride oxide mixed magnetic material is used as a magneto-optical recording medium, the light transmittance is improved.

For example, when pure iron is selected as the target material, a nitrogen gas containing oxygen (preferably argon is added) is used as the nitride oxide mixed magnetic thin film.
By irradiating the ionized material and sputtering Fe, a nitride film containing oxygen may be formed on the nonmagnetic support.

It is desirable that these nitride oxide magnetic thin films have a range of 45 atomic% ≦ M ≦ 80 atomic%, 10 atomic% ≦ N ≦ 30 atomic%, 4 atomic% ≦ O ≦ 30 atomic%. These figures indicate that the ratio of the amount of ionized gas is 10 to 80% for N _2, 10 to 80% for Ar,
By adjusting to about 15%, the desired value can be obtained.

In order to reduce the saturation magnetization of the magnetic thin film 12 and to lower the Curie temperature (Tc) of the layer 12 and to improve the light transmission of the laser light, the magnetic thin film 12 has It is effective to add fluorine.

Putting fluorine into the magnetic thin film 12 is as follows.
As a result, the fluoride of Co, Ni and / or Fe becomes Co,
It will be mixed and coexist with the nitride of Ni and / or Fe. Appropriate specific examples of the fluorides of Co, Ni and / or Fe include FeF ₂ , FeF ₃ , Fe ₂ F ₅ , C
oF ₂ , CoF ₃ , NiF _{2 and the} like.

In the magneto-optical recording medium, as described above, the Curie point (Curie temperature: temperature at which magnetization is lost and written) is too low to erase the recording during use, and if too high, the laser light output is increased. There must be. Also,
Among the magneto-optical effects, the method using the Faraday effect is greatly affected by the thickness of the magnetic thin film 12 and is required to have an appropriate light-transmitting property.

When the light transmittance of the magnetic thin film 12 is appropriate, the film is heated by absorbing the laser beam. However, when the light transmittance is poor, the Faraday rotation angle cannot be large and the S / N ratio cannot be obtained.
The ratio does not increase. However, the nitride magnetic material (M
If the N component in _xN ) is increased, the translucency can be improved and the Curie temperature can be lowered. However, if the N component is too large, nitrogen easily escapes from the film with low heating and lacks stability.

From these considerations, the nitride magnetic thin film (M _x
If fluorine is added to N), an ideal magneto-optical recording medium having a good perpendicular magnetization film and a suitable translucency and Curie temperature can be obtained. This is M _x N
(Nitride) is mixed with an appropriate amount of fluorides of Fe, Co and Ni (including amorphous) to form a thin film, so that the N component in the film is prevented from desorbing and chemically and physically stable. Probably because it became. The nitride-fluoride mixed magnetic thin film preferably has a range of 43 atomic% ≦ M ≦ 80 atomic%, 10 atomic% ≦ N ≦ 30 atomic%, 4 atomic% ≦ F ≦ 40 atomic%.

This nitride-fluoride mixed magnetic thin film can be formed by replacing “oxygen” in the ionized gas at the time of forming the nitride oxide mixed magnetic thin film with “fluorine”. This is performed by appropriately adjusting the gas ratio.

As another means for reducing the saturation magnetization of the magnetic thin film 12 and lowering the Curie temperature to improve the light transmittance, a nitride magnetic material (M _x N) is used.
It is also effective to put carbon and oxygen therein. In this case, the range of 50 atomic% ≦ M ≦ 80 atomic% 10 atomic% ≦ N ≦ 40 atomic% 2 atomic% ≦ C ≦ 45 atomic% 2 atomic% ≦ O ≦ 25 atomic% is appropriate.

Carbon not only can be easily mixed into the film, but also contributes to an improvement in light transmission. This is also true for oxygen, as described above. In addition, carbon and oxygen have the effect of not deteriorating the hcp structure and orientation of the crystal.

Carbon and oxygen may be combined with Fe, Co and / or Ni to form a crystal when forming a nitride magnetic material (M _x N), but are incorporated amorphously in the film. Is optically preferred. Depending on the quantitative combination of carbon and oxygen, the light transmittance can be controlled in a wide range of 20 to 60% using a laser beam of 500 to 900 nm when the film thickness is 1000 to 3000 °.

The formation of the nitride magnetic material (nitride carbide oxide mixed magnetic material) thin film mixed with carbon and oxygen is performed by using the “ionized gas” of the ionized gas at the time of forming the nitride oxide mixed magnetic thin film. The “oxygen” may be replaced with “carbon monoxide (CO)”, and the ionization is performed by appropriately adjusting the amount ratio of the ionized gas. As is well known or frequently mentioned, the Faraday rotation angle is proportional to the length of light transmitted through the magnetic thin film, so that the Faraday rotation angle increases as the film thickness increases.

The medium using the "Kerr effect" in the magneto-optical recording method is to reflect light on the surface of the magnetic thin film and read the recording by the rotation angle (Kerr rotation angle) at that time. In the type, an amorphous rare earth / transition metal alloy (a-rare earth / transition metal alloy) is generally used as a magnetic thin film.

The present inventor has confirmed that a magneto-optical recording medium using both the Kerr effect and the Faraday effect of a magnetic thin film described above is also useful for forming an M _x N magnetic material.

Although the magneto-optical recording medium itself simply utilizing the Kerr effect and the Faraday effect may be known in the past, a-rare-earth / transition metal alloys dislike oxygen (oxidize). On the layer, there is a defect that it is difficult to stack an oxide magnetic material (for example, Ba ferrite, Co ferrite, GdFe garnet, Bi-substituted garnet, etc.) which has been energetically studied at present.

In the present invention, it is possible to form an a-rare earth / transition metal alloy layer (amorphous alloy layer) instead of the reflective layer 13 of FIGS. The reflectance of the amorphous alloy layer is about 50% (λ ≒ 800 n
m), and has a function as a reflective layer. Since it is desirable that the a-rare earth / transition metal alloy layer and the magnetic thin film according to the present invention have similar magnetic properties, GdCo, GdFe, TbF is used for the material of the amorphous alloy layer.
e, a material having Fe and Co as main components, such as GdTbFe, TbDyFe, and TbFeCo, is used.

In this type of magneto-optical recording medium, the composition may be somewhat mixed between the a-alloy layer and the magnetic thin film according to the present invention, but both have relatively similar magnetic characteristics. There is no inconvenience due to this. Of course, the Curie temperature and the compensation temperature can be adjusted in both layers. When the a-alloy layer is located on the free surface, a protective layer (AlN, SiN, SiO, TiO, TiN,
Preferably, a thin layer of SiO ₂ or the like is provided. Further, the fact that a dielectric layer may be provided is the same as that described with reference to FIGS.

As mentioned above, the magneto-optical recording medium of the present invention can be manufactured by various film forming methods. Among them, the magnetic thin film is advantageously formed by the ion beam sputtering method.

FIG. 3 schematically shows an example of an apparatus suitable for carrying out the method of the present invention. In this apparatus, the ion gun 3 is disposed so that the tip of the ion gun 3 protrudes inside the vacuum chamber 2. The ion gun 3 is an N ₂ gas (preferably a mixed gas of N ₂ gas and Ar gas) supplied from a gas cylinder 4.
Is applied with a DC voltage of several KV to generate plasma, and the plasma can be emitted toward the target 5 from a hole in the front surface of the tip.

Here, the gas supplied from the gas cylinder 4 is N ₂ gas or a mixed gas of N ₂ gas and Ar gas. (A) The nitride magnetic thin film containing, for example, oxygen (nitride oxide) Oxygen gas is further added to the supply gas in the case of a (compound-containing magnetic thin film), and CO gas or (b) a gas containing oxygen and carbon (nitride carbide oxide-containing magnetic thin film). It is sufficient to add CO ₂ gas. For convenience, the description will proceed assuming that the magnetic thin film is a Fe _x N thin film, but there is an essential difference in the film forming means and the metal or alloy used itself. Not in translation. Now, if the target 5 is made of pure iron (purity: about 99.99%), nitrogen atoms (preferably nitrogen atoms and argon atoms) that are made into plasma sputter iron atoms of the target 5.

The sputtered iron atoms react with the nitrogen atoms in the plasma on the front surface of the target to form Fe _x N (x = 2 to 2).
3) to deposit on the surface of the nonmagnetic support 11 to form a thin film (magnetic thin film).

In this manner, the magnetic thin film 12 intended in the present invention can be formed on the non-magnetic support 11. In this thin film formation, the non-magnetic support It is highly desirable to dispose the magnet 6 so that a magnetic field mainly composed of a magnetic flux which is vertically directed to the surface of the body 11 is present.

The non-magnetic support 11 is moved by the rotating roll 7 which rotates slowly, but the non-magnetic support 11 is maintained at room temperature without being heated or cooled.

In any case, the gas supplied to the ion gun 3 is preferably made to coexist with Ar gas, which is an inert gas.

If the non-magnetic support 11 is not flexible, the holder for the non-magnetic support 11 is used instead of using the rotating roll 7.

The magnet 6 may be either an electromagnet or a permanent magnet, and the number of magnets is arbitrary. In short, as described above, any material can be used as long as it can generate a magnetic field mainly composed of magnetic flux perpendicular to the surface of the nonmagnetic support 11. The magnetic field strength should be between 10 and 5000 Gauss, preferably 1
It is set to 00 to 1000 Gauss. The degree of vacuum (gas pressure) in the vacuum chamber 2 is 1 to 10 × 10 ⁻⁵ Torr, preferably 1 to 5 × 10 ⁻⁵ Torr.

Now, as a “test example”, using this apparatus, the target 5 was made of pure iron (purity: 99.99%),
The internal back pressure was about 2 × 10 ⁻⁶ Torr, and the introduced gas was N ₂
(75%) + Ar (25%) mixed gas, the ion gun voltage is about 8.5 KV, the ion gun current is 5.5 mA, and the plasma target 5 and the plasma 5 radiated from the ion gun 3 are used. The angle of incidence on the non-magnetic support (polyester film having a thickness of about 25 μm) 11 is about 40 °.
When a film is formed, Fe atoms and N atoms in the plasma react with each other to form ε-phase Fe _x N (x = 2 to 3), and this ε-phase Fe _x N (x = 2 to 3) ) Indicates the non-magnetic support 1
Deposited oriented perpendicular to one surface, i.e., crystals ε phase on the non-magnetic support 11 aligned with the C-axis direction Fe _x N _(x = 2~
3) A thin film is formed, and thus this Fe _x N thin film is obtained as having a very large perpendicular magnetic anisotropy.
In fact, when this magnetic thin film was examined by X-ray diffraction,
(00) of ε-phase Fe _x N (x = 2 to 3) having a cp structure
2) A diffraction peak of (004) was observed, and (002)
(004) Single-phase film whose plane is largely oriented (film thickness about 2000
It is recognized is Å), also (002 half width [Delta] [theta] ₅₀ determined from rocking curve of) surface was very good alignment film is 0.5 deg. Further, the magnetic characteristics examined by VSM are as shown in Table 1.

The angle of incidence of the plasma radiated from the ion gun 3 on the target 5 and the non-magnetic support 11 is 40
Although the degree is preferable, it is not necessarily limited. For example, the moving speed of the nonmagnetic support 11 and the thickness of the deposited film [ε phase F _x N (x = 2 to 3) thin film] are considered. Can be selected as appropriate.

The magnetic recording medium having the iron nitride magnetic thin film formed on the non-magnetic support can be effectively used as a high-density magnetic recording medium. Co or Ni or F on target 5
The same applies to the case of using an alloy of two or more metals of e, Co, and Ni, or the case of using a fluoride of these metals.

A cobalt nitride magnetic thin film (thickness of about 2000) was formed under the same conditions as those for forming the iron nitride magnetic film.
Å) and nickel nitride magnetic thin film (about 2000 約 thick)
Table 1 summarizes the magnetic properties of

[0079]

[Table 1] * Approximately 2000 thickness between each nitride thin film and non-magnetic support
Ａｌ was provided with Al (reflection layer) and measured using a semiconductor laser (wavelength 780 nm, output 20 mW).

[0080]

Next, examples and comparative examples will be described. Example 1 Using a vacuum deposition apparatus, a glass substrate (Corning 705) was used.
9) A thickness of about 1000 as an underlayer under the following conditions
A thin film of Ti (underlayer) was formed. Evaporation material Ti support temperature 300 ° C. Back pressure in vacuum chamber 5 × 10 ⁻⁶ Torr Evaporation source-substrate distance 25 cm The obtained Ti thin film was examined by X-ray diffraction.
It was an axis alignment film. On this Ti thin film, using the ion beam sputtering apparatus shown in FIG. 3, the same conditions as those for forming the iron nitride thin film [however, N ₂ (75%) + Ar (25%)]
N ₂ instead of the mixed gas used (100%) gas was about 6KV the ion gun voltage, about 6mA the ion gun current]
To form a magneto-optical recording medium by forming an iron nitride thin film (iron nitride magnetic layer). This magneto-optical recording medium has a maximum of 12 KOe
A semiconductor laser (wavelength 780 n)
m, the output was 20 mW), and the Faraday rotation angle θ _FR was measured. The θ _FR value was 0.86 deg / μm. The measured value of θ _FR did not change even six months after the film formation. In the formation of the iron nitride thin film, only N ₂ gas is sent onto the target, so that it easily reacts with Fe (the same applies to Co and Ni), that is, easily turns into nitride. ₂ gas (10-90%) and Ar
The use of a gas mixture (90 to 10%) is advantageous.
This is because the use of an inert gas (Ar gas) makes it easier to obtain a nitride film having perpendicular magnetic anisotropy.

[0081] on a second embodiment the glass substrate, the same conditions as film formation of the iron nitride thin film using an ion beam sputtering apparatus shown in FIG. 3 [where, N ₂
+ Ar = 1: 1 (volume ratio) mixed gas, ion gun about 9K
V, ion gun current 2 mA, ion incidence angle 45 degrees]
Except for forming iron nitride thin casting (magnetic thin film) in the same way,
Further, an Al vapor deposition layer (reflection layer) of about 1000 ° was provided on the magnetic layer to produce a magneto-optical recording medium.

Example 3 A magneto-optical recording medium was produced by forming a cobalt nitride thin film in exactly the same manner as in Example 2 except that the target was changed from pure iron to pure cobalt (purity: 99.99%). Table 2 summarizes the characteristics of these magneto-optical recording media. Further, no change was observed in the characteristics even when the iron nitride thin film and the cobalt nitride thin film in these magneto-optical recording media were immersed in a 5% NaCl aqueous solution for 200 hours.

Comparative Example 1 Iron-containing gaseous molecules and nitrogen-containing gaseous molecules were introduced into a reduced-pressure reaction vessel, and an electromagnetic wave was applied to these gases to cause a plasma reaction to occur. Was formed on a glass substrate. When this iron nitride thin film was examined by X-ray diffraction for a thin film, F ₃ N (002) and F ₃ N
e ₄ N (001), Fe ₃ N (101) and α-Fe (11
The diffraction peak of 0) was observed. This thin film is considered to have insufficient orientation and to be iron or a mixed nitride of each crystal form. A magneto-optical recording medium was manufactured by providing an Al vapor-deposited layer having a thickness of about 1000 ° on the iron nitride thin film. Table 2 summarizes the characteristics of this product.

[0084]

[Table 2]

Examples 4 to 8 In the above test examples, the magneto-optical recording medium was manufactured in the same manner as in the above test examples except that the nonmagnetic support was a glass plate, the ion incident angle was 45 °, and the conditions were changed as shown in Table 3. I made it.

[0086]

[Table 3]

In these magneto-optical recording media, the magnetic thin film of Example 4 was examined by X-ray diffraction.
C-plane (002) (004) of ε-phase iron nitride having p-structure
Strong diffraction peak was observed. Also, very small diffraction peaks of Fe ₂ O ₃ were observed. The content of iron oxide determined by using XPS (X-ray photoelectron spectroscopy) was 4% by weight. Table 4 summarizes the results of measuring the magnetic properties with the VSM.

When the magnetic thin film (the magnetic thin film mixed with cobalt nitride iron oxide) of Example 5 was examined by X-ray diffraction, it was found that it was a C-axis oriented film of ε-phase Co nitride having an hcp structure. Was. The O (oxygen) content determined using XPS was about 9 atomic%. Table 4 summarizes the measurement results of the magnetic characteristics with the VSM.

When the magnetic thin film of Example 6 (iron nitride nitride-cobalt nitride-iron oxide mixed magnetic thin film) was examined by an X-ray diffraction method, it was found that (002) of ε-phase iron nitride and ε-phase (004) A diffraction peak was observed. However, the intensity of the diffraction peak is not so strong, and it is considered that these amorphous components are contained. Also, a very small diffraction peak of Fe ₂ O ₃ was observed.
The content of O (oxygen) examined using XPS is about 13 at.
omic%. Table 4 summarizes the measurement results of the magnetic characteristics with the VSM.

When the magnetic thin film of Example 7 was examined by an X-ray diffraction method, a diffraction peak of an ε-phase iron nitride having an hcp structure was observed, and it was recognized that the magnetic thin film had a C-axis orientation. Further, a minute peak of FeF ₂ was observed. XP
The F content determined in S was about 16 atomic%. Table 4 summarizes the results of measuring the magnetic properties with the VSM.

Further, when the magnetic thin film of Example 8 was examined by X-ray diffraction, it was confirmed that the magnetic thin film was an ε-phase cobalt nitride having an hcp structure, and that it was C-axis oriented. . When measured by XPS, it was Co 62.5 atomic% N 13.5 atomic% O 11.7 atomic% C 12.5 atomic%. Table 4 summarizes the measurement results of the magnetic characteristics with the VSM.

[0092]

[Table 4]

Example 9 A total gas pressure of 3 was applied onto a glass substrate 11 by RF sputtering.
mtorr, input power 1KW, distance between substrate targets 6
0 mm, deposition rate 1000 ° / min, target Tb
_{20 (Fe 0. 9 Co 0} . 1) was formed amorphous alloy layer about 800Å thick under the conditions of alloy (TbFeCo film). The substrate was water cooled. On this amorphous alloy layer, the same method as in the test example (however, the ionized gas is a mixed gas of N ₂ + Ar = 1: 1, the ion gun voltage is 8 KV, and the ion gun current is 2.5 m
A, the ion incidence angle was 45 degrees), and a magnetic thin film (iron nitride thin film) having a thickness of about 2000 ° was formed to produce a magneto-optical recording medium. The magnetic thin film was an ε-phase iron nitride having an hcp structure, and was found to be C-axis oriented.

A semiconductor laser beam (wavelength 780 nm) is applied to this magneto-optical recording medium while applying a maximum magnetic field of 12 KOe.
The measured magneto-optical effect was 1.4 degrees. This value did not change in the measurement after 6 months.

[0095]

According to the magneto-optical recording medium of the present invention, since the light transmittance is high and the Faraday effect is large, good recording and
Playback is possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of a typical magneto-optical recording medium according to the present invention.

FIG. 2 is a sectional view of another example of a typical magneto-optical recording medium according to the present invention.

FIG. 3 is a schematic view for explaining desirable means for manufacturing the magneto-optical recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical recording medium 2 Vacuum tank 3 Ion gun 4 Gas cylinder 5 Target 6 Magnet 7 Rotating roll 11 Nonmagnetic support 12 Magnetic thin film 13 Reflective layer

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 63-197521 (32) Priority date August 8, 1988 (33) Priority claim country Japan (JP) (31) Priority Claim No. Japanese Patent Application No. 63-281991 (32) Priority date November 7, 1988 (33) Priority claiming country Japan (JP)

Claims (1)

(57) [Claims] 1. Co, Fe and Ni on a non-magnetic support
A magneto-optical recording medium characterized by comprising a magnetic thin layer having a perpendicular magnetic anisotropy and comprising a nitride of at least one metal selected from the group consisting of a main component and an oxide of the metal.