JPS6187243A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a photomagnetic recording medium which has a high S/N ratio and permits high-density recording and high-speed recording by forming said medium so as to have a photomagnetic recording layer consisting of an alloy added with specific elements and a low coercive force material layer consisting of a specific alloy and dominently amorphous alloy. CONSTITUTION:The photomagnetic recording medium has the photomagnetic recording layer consisting of the alloy composed of elements of at least &i1 kinds of Ce, Pr and Nd as well as Fe and impurities or said alloy added further with elements of >=1 kinds among B, C, Si, P and Al and the alloy added with elements of >=1 kinds of Cr, Co, Cu, Ni and Mn to said alloy and the low coercive force material layer of which the coercive force is <=1/5 the coer cive force of the photomagnetic recording layer and <=100 oersted and which consists of the alloy composed of elements of >=1 kinds of Si, B and P as well as Fe and impurities of the alloy added with further >=1 kinds among Co, Ni, Cr, Mo and W to aid alloy and the dominantly amorphous alloy.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a magnetic recording medium that has an axis of easy magnetization in a direction perpendicular to the film surface and can be read using magneto-optic effects such as the magnetic Kerr effect. It is.

Research on magneto-optical memory began in 1957 with M? It is said that the origin of this technology is that a hot pen was used to record on a ZBz thin film, and the written magnetic domain was observed using the magneto-optic effect. Spurred by subsequent developments in lasers, Mn
Although intensive research has been carried out mainly on B1-based materials, practical use has not been achieved because laser light sources and the technology for using them are still immature.

However, in the 1970s, advances in optical information processing related technology and research into new magnetic thin film materials such as amorphous rare-earth transition metal alloy thin films progressed.
-87607) GdFe, T6F#.

Alloy thin films such as DyFg and GdC0 have been developed. These materials generally have the following characteristics.

Compensation point recording magneto-optical recording media such as GdFe and GdCo have a larger Kerr rotation angle than Curie single-point recording magneto-optical recording media and have excellent optical reproduction characteristics, but have a small coercive force (several hundred oersteds) of 1 μm. It is not possible to stably obtain bits as small as TbFg, Dy'? Contrary to the above, magneto-optical recording media for Curie single-point recording such as No. 6 have a large coercive force (several kilo Oersteds). Although it is possible to stably obtain a minute bit with a diameter of about 100 mm, it has disadvantages such as a small Kerr rotation angle and poor optical reproduction characteristics.

Furthermore, Tb, Chi, Dy, Ho, etc., and heavy rare earths are expensive and unsuitable for practical use.

In order to compensate for the drawbacks of these binary alloy thin films, eight methods have been tried in the past.

(1) To become ternary or quaternary. For example, the binary Gdy
GdTbF takes advantage of the strengths of , and T6F, and compensates for their weaknesses.

Ternary alloy or Gdl? 'bMethod of diversification like FlCQ quaternary alloy (Unexamined Japanese Patent Publication No. 56-126907
゜(2) A method of improving the properties of the binary alloy thin film by improving the manufacturing method or using a new manufacturing method, (Japan Society of Applied Magnetics, Nth Research Meeting Material 27-5) (8) A method of creating a multilayer structure . A dielectric layer is layered on the recording medium to increase the Kerr effect due to multiple reflections.

Also, the recording layer and reproduction layer are separated, and materials suitable for each are used. Alternatively, a reflective layer may be provided on the back side of the recording medium to reflect and utilize not only the light reflected from the surface but also the light that has passed through the medium. (% opening 58-
200447) In addition, there are also systems in which heavy rare earth-transition metals are used for magneto-optical recording and permalloy, F's, Co, and Ni are used instead of the reflective film (Japanese Patent Laid-Open No. 58-222455), but the bits do not exist stably. Permalloy, 'F
Since e, co, and l are polycrystalline, they cause noise and lead to deterioration of S and A1.

However, in these methods, although the Kerr rotation angle increases, the reflectance decreases. Furthermore, even if the Kerr rotation was improved to some extent, there were advantages and disadvantages, such as the Curie temperature becoming higher and laser writing becoming difficult, and no fundamental improvement was achieved.

〔the purpose〕

The present invention fundamentally improves the above-mentioned drawbacks such as the small Kerr rotation angle and the inability to stably obtain 1 μm bits.
It improves contradictory characteristics and is high.

The purpose of the present invention is to provide a magneto-optical recording medium with high density, high stability, and high speed read/write capabilities.

〔overview〕

The present invention provides a magneto-optical recording medium that performs recording and reproduction by irradiating light onto a magneto-optical recording layer in which the direction of magnetization is perpendicular to the film surface and has a binary value of either upward or downward. #), praseodymium (Pr) neodymium (Nd)
An alloy consisting of at least one of the following elements, iron (7g) and impurities, or the alloy further contains boron (B).
, carbon (C), silicon (8), phosphorus (P), aluminum (aluminum), an alloy to which at least one or more elements are added, or the alloy further contains OA (Cy), : x Part (Co), copper (C1L), nickel (Ni), and manganese (M, L); , and less than 100 oersted silicon (S<).

An alloy consisting of at least one element selected from boron (B) and phosphorus (P), iron (Cug), and impurities.

Alternatively, the alloy may be further added with cobalt (CO), nickel (
The material is made of an alloy to which at least one of Ni), chromium (Cr), molybdenum (MO), and tungsten (W) is added, and is characterized by having a low coercive force material layer made of a predominantly amorphous alloy. .

[lol example]

The present invention will be explained in detail below using the drawings.

The basic structure of the present invention is shown in Fig. 1 Ca) and Fig. 1 Cb).

11 is a substrate, 12 is a magneto-optical recording layer, 13 is a low coercive force material layer, and 14 is a nonmagnetic layer.

In addition, in ζ, the substrate is a transparent substrate such as glass plastic, and the optical head for reading and writing faces the substrate side, and I wrote that reading and writing is done through the substrate, but this is not essential, and the substrate is made of low resistance. There is no problem even if it is formed with a magnetic material layer, magneto-optical recording layer, or a low coercive force material layer, a non-magnetic layer, and a magneto-optical recording layer, and the optical head is placed facing the magneto-optical recording medium side with respect to the substrate to read and write. Further, the present invention is not limited to the above-mentioned structure, and it is possible to provide a protective film, an anti-reflection film, a multiple interference enhancement film, a transparent conductive film, etc.

(1) Using a well-cleaned glass as the substrate Z in a medium having the structure shown in FIG. -n, and an amorphous film 21 was formed thereon by sputtering. Il above
', s<B The coercive force of the amorphous film is about 7 oersted, and is assumed to be sample/IfLl. Also, for comparison, the above y, s7
Sample point 2 is obtained by forming 100 OA of KAA by sputtering instead of the B amorphous film.

(2) With a medium having the structure shown in FIG. 2(b), (1)
Similarly, glass substrate-22 is Hd'F, B film-21
is v, azB film, and sho is dielectric layer, 800X
It is formed.

This enhances the Kerr rotation angle by forming a 5ho2 film between Nd'F, Bi and the glass substrate. This is designated as sample A8. Also, for comparison, the above Fg
A instead of S-jE amorphous film! 100 by sputtering method
The one formed with 0A is designated as sample &4.

(8) A medium having the structure shown in Fig. 2 (C) (Same as the odor, O is a glass substrate, n is HdF, B film, and 21 is Fg
S7B film-24 is B-02 film #25 Hiro8so2
It is formed between the NdFeB film and the Fe8jB film using JIk, and has a thickness of too'A.

Let's use this as sample A5 for comparison? d8jB film A! The sample replaced with a membrane is designated as sample A6.

(4) A medium having the structure shown in Figure 2 (F), where 3 is PM
It is an MA substrate and has guide grooves with a spacing of 1.6 μm and a depth of 700×. Also, as in (1), Vc22 is N(
9eB de-21 is y6s4. This is a B film. This is designated as sample point 7.

Also, for comparison, instead of 1e8iB amorphous film! The sample on which the film was formed is designated as sample A8.

(6) Using a medium having the structure shown in FIG. 2 (61) and using the same PMMA as in (4) as the substrate part, the same 8i0-dFgB/l as in sample A8 in ■)? ', 5i13 structure is designated as sample point 9, and for comparison, F$SjB of sample A9
Let AA be sample point 10.

(6) A medium having the structure shown in Fig. 2, using the same PMMA as in (4) as the substrate 26, and the same sz○v/NdF6B/570v'EgBsB as in sample A5 in (2).
The structure is called sample A11, and sample point 1 is used for comparison.
1 of Fe51:E ) i5 A! sample point 1
Set it to 2.

(7) In a medium having the structure shown in FIG. 2 (α), is II', sH:s at sample point 1 in (1) 1? 'gc(, s4B) is sample A13.

The coercive force of this 2c6s4B is about 5 Oersteds.

(8) Sample 414 is a medium having the structure shown in FIG.

The coercive force of F and N4p is approximately 6 Oersteds.

(9) Sample point 15 is a medium with the structure shown in FIG.
A! This is designated as sample &16.

(O In a medium with the structure shown in Figure 2 (α), the amorphous N of (1)
Sample point 17 is the one in which dteB is C#F11&#C with a thickness of 500A, and Fe5jB of sample A17 is used for comparison.
A! This is designated as sample A18. .

0 A medium having the structure shown in FIG. 2 (α), with NdFgB t-kldPrFe at sample point 1 in (1) as sample A19, and for comparison, FgS7B of sample 19 was used as A! This is designated as sample A20.

(12) Sample point 21 is a medium having the structure shown in FIG. 2(a), in which NdFeB of sample A1 in (1) is replaced with NdFe5iCo. For comparison, v and s6B of sample point 21 are A! Let this be the sample &ρ.

(3) In the medium having the structure shown in Fig. 2 (g), the NdFeB at sample point 9 in (5) is set to Tb1l'.
3, and for comparison, F$SzB of sample AZ3 is A! The bound part is used as the sample plate.

The Kerr effect was measured for the above types of samples. The Kerr effect was measured by applying a magnetic field of 10 kA to the sample to make it into a remanent magnetized state (He-N).

Measurement was performed using a gas laser (wavelength: 682.8+1 meter). The measurement results are shown in Table 1F.

In Samples 1 to 12 of (1) to (6), the Kerr rotation angle of all structures using amorphous Fe54B is approximately twice as large as that of AJ. In addition, even when Fe-based amorphous thin films other than F', 8<B are used in Samples 13 and 14 of (8), there is still an increase of about twice the AJ of Sample 2. Ta.

(9) P7FeB as the recording layer in ~42,
C, IFgAJC, NdPr'? e, N47g8S
The Kerr rotation angle also increased in the case of CO.

α3 is T
The Kerr rotation angle was measured using bFe as the recording layer, and even in this case it increased by about 1.5 times.

The magneto-optical recording medium has c, , y6, c, , M
The material to which n was added had the same effect as the addition of CO in Sample 21, had excellent weather resistance, and was a magneto-optical recording medium having an axis of easy magnetization perpendicular to the film surface.

Furthermore, as a specific example of the F-based amorphous low coercive force material layer, at least one of FsKBt, B, and P is added, and further, c,) and 17 are added to improve weather resistance. However, Cf, MQ, and W had exactly the same effect.

Example 2 The relationship between the coercive force of the low coercive force material layer and the Kerr rotation angle was investigated. The results are shown in FIG. 8, where the horizontal axis is the coercive force and the vertical axis is the Kerr rotation angle. All samples used are shown in Figure 2(a).
has the structure, α is glass/NdFgB/
FgSjB, 'b is glass/HdleBAPe
CQBiB, e is glass/T6? , /EF, 8-vertical. The Kerr rotation angle increases as the coercive force of the low coercive force layer becomes smaller for all three species a and bC. However, when the coercive force reaches about 100 Oersted, it is equivalent to that of an AJ with a reflective layer. (d, e in the figure) If the coercive force becomes even larger, it is actually 8! The Kerr rotation angle is smaller than that. Does this mean that the reflectance is higher than that of A7?
, this is because the system alloy is small.

Table 1 Example 8 Using an optical head capable of magneto-optical recording and reproduction h1 Fig. 4 (α)
The frequency characteristics were investigated using the media structure shown in the figure. A semiconductor laser with a laser wavelength of 780 wx was used.

The disk rotation speed was fixed at 1800 rpm and the radius was fixed at 5 cIn, and the writing frequency was varied. Reading and writing were performed from the board side. The board is polycarbonate 4 with groups.
1, and a thin film as shown in Table 2 was formed to have an 8-layer structure. The first layer is A 7 N 42 with an 80 OA, the second layer is a magneto-optical recording layer 43 with a 100 OX, and the eighth layer is a conventional AJ reflective film or an amorphous film according to the present invention. , the system resistance magnetic film 44 was p6sin and had a film thickness of %50QA. The forming means was a DC magnetron sputtering method. FIG. 4(b) shows the ≠ratio with respect to the writing frequency in each magneto-optical recording medium. Compared to the conventional case where non-magnetic AA is used as a reflective film, the present invention's amorphous? , C/Hrαtio increased by providing a system resistive magnetic layer. moreover,
According to the present invention? In magneto-optical recording media containing at least one of Ce, Pr, and Nd, the effect is even greater, and the writing frequency characteristics are dramatically improved.

Table 2 (Composition units are expressed in atomic units) [Effects] As shown in the above examples, the magneto-optical recording medium having the structure according to the present invention has a Kerr rotation angle that is almost doubled and a C
The 7M ratio is also improved.

Furthermore, since the recording magnetic domain is stable, there is little deterioration in the 07M ratio even at high recording densities, making the medium more suitable for high-density recording.

In addition, conventional Tb'Fe, GdCo, Tbl1''e
Compared to media containing heavy rare earths such as Co and TbGdFg, materials containing light rare earths such as Nd, Dτ, and Ce are cheaper in material cost, and the magneto-optical recording medium according to the present invention has lower material costs than media containing heavy rare earths such as Co and TbGdFg. It has the characteristic that the effect is greater.

Is the recording layer on the recording medium because it is amorphous? It is very easy to grow an amorphous F, or, conversely, to grow an amorphous magneto-optical recording layer on an amorphous F, amorphous layer.

[Brief explanation of the drawing]

FIGS. 1(c) and 1(b) show the basic layer structure of the magneto-optical recording medium according to the present invention. FIGS. 2(a) to 2(a) show the structure of a specific example of the magneto-optical recording medium according to the present invention. FIG. 8 is a diagram showing the effect of the low coercive force material layer of the present invention, in which the Kerr rotation angle of the magneto-optical recording layer is plotted against the coercive force of the low coercive force material layer. FIG. 4(b) is a diagram showing the writing frequency characteristics of the magneto-optical recording medium of the present invention. The structure of the magneto-optical recording medium is shown in FIG. 4(CL), and the magneto-optical recording layer is changed in various ways. This is an example showing the effects of the present invention. that's all

Claims (1)

[Claims] In a magneto-optical recording medium in which recording and reproduction are performed by irradiating light onto a magneto-optical recording layer in which the direction of magnetization is perpendicular to the film surface and has a binary value of upward or downward, the magneto-optical recording medium is made of cerium (C).
e) An alloy consisting of at least one element selected from praseodymium (Pr) and neodymium (Nd), iron (Fe), and impurities, or the alloy further contains boron (B),
An alloy to which at least one element among carbon (C), silicon (Si), phosphorus (P), and aluminum (Al) is added, or to the alloy, chromium (Cr), cobalt (Co), copper (Cu), Nickel (Ni), manganese (
A magneto-optical recording layer made of an alloy to which at least one element of Mn) is added, and a magneto-optical recording layer having a coercive force of less than one-fifth and less than 100 Oe
an alloy consisting of at least one element among Si), boron (B), and phosphorus (P), iron (Fe), and impurities;
Alternatively, the alloy may be further added with cobalt (Co), nickel (
It is characterized by comprising an alloy to which at least one of Ni), chromium (Cr), molybdenum (Mo), and tungsten (W) is added, and a low coercive force material layer comprising a predominantly amorphous alloy. magneto-optical recording medium.