JPH01116945A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To lower only the Curie point of thin amorphous alloy films without changing the magneto-optical characteristics thereof by alternately laminating >=2 layers of the thin amorphous alloy films and metallic films and specifying the film thicknesses thereof to the small thicknesses within a specific dimensional range. CONSTITUTION:This magneto-optical recording medium 10 is constituted by alternately laminating at least >=2 layers of the thin amorphous alloy films 2 contg. a rare earth metal and transition metal and the metallic films 4. Protective films 6 for preventing the oxidation of the thin amorphous alloy films 2 and a substrate 8 for imparting adequate rigidity to the recording medium 10 are provided. The thicknesses of the respective thin amorphous alloy films and the thicknesses of the respective metallic films are specified to 5-200Angstrom . Only the Curie point of the thin amorphous alloy films is thereby lowered without changing the magneto-optical characteristics possessed by said films.

Description

[Detailed Description of the Invention] 1. The present invention relates to an optical recording medium having a multilayer amorphous alloy thin film, and more specifically, the present invention relates to an optical recording medium having a multilayer amorphous alloy thin film, and more specifically, the present invention relates to an optical recording medium having a multilayer amorphous alloy thin film. The present invention relates to a magneto-optical recording medium whose Curie point is lowered.

Technical background of the invention and its problems Transition metals such as iron and cobalt, terbium (Tb),
Amorphous alloy thin films made of alloys with rare earth elements such as gadolinium (Gd) have an axis of easy magnetization perpendicular to the film surface, and light is applied to a part of the film surface that is magnetized in one direction. By focusing the irradiation, a small reversal occurs in the direction opposite to this overall magnetization direction.

It is known that magnetic domains can be formed.

By associating the presence or absence of this inverted magnetic domain with "1" and "0", it becomes possible to record digital signals on the amorphous alloy thin film as described above, so-called magneto-optical recording.

In an optical recording medium that uses an amorphous alloy thin film capable of magneto-optical recording as a recording layer, in order to read information recorded in the recording layer, it is generally necessary to inject light such as a laser beam into the recording layer. This is done by focusing the light and reading the Kerr rotation angle of the light rotated by the Kerr effect. The Kerr rotation angle is an angle determined by the material of the amorphous alloy thin film that makes up the recording layer.The larger the Kerr rotation angle, the more clearly it becomes possible to distinguish information, and the more errors occur when reading information. decreases. Therefore, the amorphous alloy thin film used as the recording layer is required to have a large Kerr rotation angle.

However, in general, amorphous alloy films with a large Kerr rotation angle,
It is known to have a high Curie point (300-450°C) (Materials from the 42nd Japan Society of Applied Magnetics Research Meeting,
42-1.1985. (pages 1-9). It is preferable that the Curie point of the amorphous alloy used as the recording layer is lower.
Generally, 100 to 200°C is considered optimal. this is,
When recording information on such a recording layer, if the recording layer has a high Curie point, the recording laser output must be increased, and in reality, a recording layer with a Curie point of 200"C or higher is required. This is because it was not possible to record and erase information at high speed.

Therefore, there has been a demand for a recording layer of a magneto-optical recording medium that does not lower the Kerr rotation angle and has a low Curie point.

By the way, in order to improve the coercive force of the recording layer, PtM
Magneto-optical recording media in which amorphous magnetic films made of nSb etc. and magnetic films made of Tb1''e etc. are alternately laminated (Journal of the Japan Society of Applied Magnetics 11(2), 173゜1987)
, a recording medium in which magnetic films made of Ni3Fe or the like and magnetic films made of γ-FeMn or the like are alternately laminated in order to improve magnetic properties (10th Japanese Society of Applied Magnetics Academic Lecture Abstracts, p. 409. 1986> etc. However, with such a recording medium, it was not possible to expect the effect of lowering the Curie point without lowering the Kerr rotation angle.

The present invention has been made in view of the above circumstances, and although the Kerr rotation angle in the recording layer is improved, the Curie point of the material constituting the recording layer is lowered. An object of the present invention is to provide a magneto-optical recording medium on which information can be easily written or read.

In order to achieve this object, the magneto-optical recording medium according to the present invention has at least two or more layers of an amorphous alloy thin film containing a rare earth metal and a transition metal and a metal film alternately laminated. , each of the amorphous alloy thin films has a thickness of 5 to 200 layers, and each of the metal films has a thickness of 5 to 200 layers.

According to such a magneto-optical recording medium according to the present invention, two or more layers of amorphous alloy thin films and metal films are alternately laminated, and the thickness of these films is about 5 to 200. It becomes possible to lower only the Curie point of the amorphous alloy thin film without changing its magneto-optical properties. Therefore, even an amorphous alloy thin film that originally has a high Curie point can be made to have a low Curie point while maintaining a large Kerr rotation angle. Therefore, by making an amorphous alloy thin film made of a material with a Curie point TC of 200'C or more, which could not be used until now due to the relationship with the radar output, with the above structure, it can be used as a recording layer in a magneto-optical recording medium. It becomes available for use.

1st row L1 ship relic” Hereinafter, the configuration of the present invention will be explained in more detail.

In the present invention, for example, as shown in FIG. 1, at least two or more amorphous alloy thin films 2 containing rare earth metals and transition metals and metal films 4 are laminated alternately to form a magneto-optical recording medium.
It consists of 0. In FIG. 1, the symbol "6" is a protective film for preventing oxidation of the amorphous alloy thin film 2, and the symbol "8" is a protective film for imparting appropriate rigidity to the magneto-optical recording medium 10. It is a board.

The present invention is not limited to the configuration shown in FIG. 1, but can be modified in various ways. For example, a relatively thick metal film (
It can also be laminated on a non-magnetic layer).

[Substrate] The substrate 8 is preferably transparent, and specifically, in addition to inorganic materials such as glass and aluminum, it is made of polymethyl methacrylate, polycarbonate, a polymer alloy of polycarbonate and polystyrene, and a non-transparent material as shown in US Pat. No. 4,614,77B. Organic materials such as crystalline polyolefins, poly4-methyl-1-pentene, epoxy resins, polyethersulfofones, polysal7ones, polyetherimides, etc. can be used.

[Protective film] The protective film 6 is for protecting the amorphous alloy thin film 2 on the outermost layer side, and is made of a material that is transparent enough to allow recording light to pass through, and that is transparent to the amorphous alloy H film 2. It is required to be non-magnetic so that it does not have any magnetic influence.

As the material for the protective film 6 that can satisfy the above conditions, an inorganic material such as silicon dioxide (Sin2) is preferably used, but other materials may also be used.

[Amorphous Alloy A Film] The amorphous alloy thin film 2 is an optical recording film that can record and reproduce predetermined signals by converging and irradiating light. In the present invention, the recording layer for recording or reproducing information has a multilayer structure made of amorphous alloy 11S12.

The amorphous alloy thin film 2 contains transition metals such as iron and cobalt,
It is an amorphous thin film made of an alloy with rare earth elements such as terbium (Tb) and gadolinium (Gd), or an alloy containing other materials (for example, oxide magnetic materials such as garnet), and the direction perpendicular to the film surface. It has an axis of easy magnetization. In the present invention, the amorphous alloy thin film 2 is made of, for example, the following components, although not particularly limited.

The amorphous alloy thin film 2 according to the present invention consists of (i) at least one element selected from 3D transition metals, (ii) at least one element selected from >rare earths, and (i) other elements. There is.

(i>3dl transfer metals include Fe, Qo, Ti, V,
Cr, Mn, Ni, Cu, Zn, etc. are used, and among these, Fe, Go, or both are preferable.

The 3d transition metal is present in the amorphous alloy thin film 2 in an amount of preferably 5 to 80,000 atomic %, more preferably 5 to 75 atomic %, particularly preferably 5 to 70 atomic %.

In addition to the above (i), the amorphous alloy film 2 includes (i) at least one rare earth element selected from the following group.

Gd, Tb, Dy, Ho, Er, Tm 1Y
b.

lu, La, Ce, Pr SNd 1P
m, 5llI.

l Of these, Gd 1Tb-DV 1HOs Nd -Sm
.

pr is preferably used.

At least one rare earth element selected from the above group is preferably present in the amorphous alloy '7a film 2 in an amount of 5 to 50
It is present in an amount of atomic %, more preferably 8 to 45 atomic %, particularly preferably 10 to 40 atomic %.

In the present invention, in addition to the above (i) and (ii), (if
) as its fractional elements, Nr, T;, pt.

Pd, Nb, Ta, Qr, etc. may be included in the amorphous alloy thin film 2 to improve corrosion resistance.

The amorphous alloy thin film 2 having the above-mentioned composition has an axis of easy magnetization perpendicular to the film surface, and most exhibit a rectangular loop with good Kerr hysteresis and are capable of perpendicular magnetic and magneto-optical recording. It is confirmed by wide-angle X-ray diffraction that it becomes a thin film.

Note that a rectangular loop with good Kerr hysteresis means that the saturated Kerr rotation angle (1 for θ), which is the Kerr rotation angle at the maximum external magnetic field, and the residual Kerr rotation angle (mu, 1), which is the Kerr rotation angle at zero external magnetic field. ) means that the ratio θ to 2/θ to 1 is, for example, 0.8 or more.

Particularly preferably, the amorphous alloy film 2 is Tb FeC0 or Gd-Tb Fe co.

When the amorphous alloy film 2 is TbFeCo, Co
The atomic % of / (Fe 10 Go > is preferably 2o to 8o −, and when it is Gd Tb Fe Go, Go
The atomic % of / (Fe + GO> is preferably 10 to 60.

[Metal film] The materials constituting the metal film 4 include Fe, co, Ni, Cr,
3d transition metals such as Ti or alloys thereof are preferred. In addition to the above-mentioned materials, the material constituting the metal film 4 is Z
r, Ta, Nb, Pd, Pt.

An alloy containing CIJ, A(1, AU, Zn, etc.) may also be used.

[Film Thickness] The film thickness of the @ layer of the magneto-optical recording medium according to the present invention is 5 to 200 layers, preferably 20 to 200 layers for the amorphous alloy thin film 2, and 5 to 200 layers, preferably 20 to 200 layers for the metal l1i4. is 5
~100 people, particularly preferably 5 to 50 people. If the thickness of these films is less than 5 Å, both films are mixed together and a laminated structure is not formed, which is not preferable. In addition, if the thickness of these films is 200 Å or more, the amorphous alloy 1pj42
It is not preferable because it cannot lower the Curie point of 200° C. or lower and requires a high-output laser device for recording, which is not practical.

The thickness of the protective film 6 is not particularly limited, but may be 650 mm.
As good as a human being.

The total film thickness of the magneto-optical recording medium 10 is 50 to 500 mm.
0 people, preferably 50 to 2000 people.

[Lamination method] As a method for alternately laminating two or more layers of the amorphous alloy thin film 2 and the metal film 4, a vacuum steaming method, a sputtering method, etc. are used, an alternate film deposition method by target switching, a substrate A rotation method etc. can be considered.

As described above in detail, according to the magneto-optical recording medium of the present invention, two or more amorphous alloy N films and metal films are alternately laminated, and the thickness of these films is 5 to 200 mm. Since the temperature is about the same as that of a human, it becomes possible to lower only the Curie point of the amorphous alloy thin film without changing its magneto-optical properties.

Therefore, even an amorphous alloy thin film that originally has a high Curie point can be made to have a low Curie point while maintaining a large Kerr rotation angle. Therefore, by making an amorphous alloy thin film made of a material with a Curie point TC of 200°C or higher, which could not be used until now due to the relationship with laser output, with the above structure, it can be used as a recording layer in a magneto-optical recording medium. It becomes available for use.

Therefore, according to the present invention, although the Kerr rotation angle in the recording layer is improved, the Curie point of the material constituting the recording layer is lowered, making it much easier to write or read information than in the past. It exhibits an excellent effect.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Below, the present invention will be roughly explained based on specific examples.

Examples 1 to 4 and t◆(1) In this example, Tb3gFe61 was used as
The present invention relates to a magneto-optical recording medium as shown in FIG. 1 in which a metal thin film is used.

As targets, (1) a composite target in which Tb chips are arranged on a Fe target at a predetermined ratio, and (2) F
(1) and (1) were deposited on a glass substrate using an e-target, the substrate was controlled to a room temperature of 20 to 30°C by water cooling, and the target was alternately switched during film formation by RF magnetron sputtering. A laminated film with 2) was formed.

The thickness of each layer is 30 for the Tb Fe amorphous magnetic layer, and 30 for the Tb Fe amorphous magnetic layer.
The e-tier consisted of 5 to 30 people. The number of lamination cycles was set so that the total lamination thickness was about 2000 layers. The Kerr rotation angle and reflectance were measured from the glass substrate side (λ
=633nm).

The results are shown in Table 1.

In Table 1, θ is the Kerr rotation angle, R is the reflectance, Hc is the coercive force, and TC is the Curie point.

Examples 5 to 8 and Comparative Example 2 Next, Table 2 shows examples in which magneto-optical recording media were formed in the same manner as Examples 1 to 4 except that TI)28Fe50co24 was used as the amorphous alloy thin film. show.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a magneto-optical recording medium according to an embodiment of the present invention. 2... Amorphous alloy thin film 4... Metal film 6...
Protective film 10...Magneto-optical recording film agent
Patent Attorney Shunichi Suzuki

Claims (1)

[Scope of Claims] 1) At least two or more layers of amorphous alloy thin films containing rare earth metals and transition metals and metal films are alternately laminated, and each of the amorphous alloy thin films has a thickness of 5 to 200 Å. A magneto-optical recording medium, wherein each of the metal films has a thickness of 5 to 200 Å. 2) The rare earth metal is Sm, Nd, Pr, Eu, Gd,
At least one selected from Tb, Dy, and Ho,
2. The magneto-optical recording medium according to claim 1, wherein the transition metal is at least one selected from Fe, Co, and Ni. 3) The metal film is Fe, Co, Ni, Pd, Pt, Ti
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is at least one selected from the following.