JPH03181039A - Magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording medium having a magnetic thin layer having a novel layer structure and a novel composition.

Conventionally, amorphous magnetic alloy films Gd=Co, Gd-Fe, Tb-Fe,
Gd-Tb-Fe, D7-Tk-Fe, etc. have been used, but their magneto-optical properties, Kerr or Faraday rotation angles are insufficient, and the S/N during reproduction is low. There are some materials, such as Gd-Tk-Fe, whose Kerr rotation angle improves when the Curie temperature is raised, but the Kerr rotation angle is still insufficient, and a high Curie temperature also requires high laser power during recording. There is.

Therefore, the present inventors have already proposed using a TkFeCo alloy as a magnetic film of a magneto-optical memory material to increase the Kerr rotation angle. However, although the Kerr rotation angle is improved by using TkFeCo, the magneto-optical properties are not fully satisfactory. Furthermore, since the Curie temperature is high, it is necessary to increase the laser power during recording, and as a result, there is a problem in that it is difficult to obtain a sufficient recording speed.

The present invention has been made in view of the above problems, and includes transition metals (Fe, Co) and rare earths (D7.Tb, Gd).
We selected a magnetic alloy composition with a large Kerr or Faraday rotation angle, focusing on the fact that the magnetic moment of the transition metal mainly acts on the magneto-optical effect in alloy thin films with By properly combining transition metals with rare earth elements and adopting a new layer structure, we succeeded in developing a magneto-optical recording medium that can record with small energy and obtain a large Sin during reproduction. It has been completed.

An object of the present invention is to provide a magneto-optical recording medium with low laser power on the memory medium surface during recording. Another object of the present invention is to provide a magneto-optical recording medium with a large Sin, ie, Kerr or Faraday rotation angle during reproduction.

The magneto-optical recording medium of the present invention has a structure in which a high refractive index layer, a magnetic thin layer, and an antioxidant layer are sequentially provided on a substrate, or a magnetic thin layer, a high refractive index layer, a reflective layer, and an antioxidant layer are sequentially provided on a substrate. and the magnetic thin layer has the general formula % formula %) (where Ml represents Tb, Gd or Dr, and Mll
is Tb.

)1-z (In the formula, MI represents Tb, Gd or Dy, MII has one different f, and 0.0<x<1.0.0.
7≦y<1. o and Q,,j < ! <0.3. ) is characterized by comprising at least one kind of magnetic alloy film represented by:

In the composition of the magnetic thin layer in the present invention, the Kerr or Faraday rotation angle is improved by the two transition metals, Fe and Co, and the perpendicular anisotropy and Curie temperature are adjusted by the combination of the two rare earth elements. be inferior. Typical examples of alloy compositions used in the magnetic thin layer of the present invention include the following.

(Tko-sDFo-s)o-a2(Feo, @Coo
, z) o-ts --h).

(Tbo, 5Bio, 1) o, +y (Feo, ysCo
o, zz) o, s3- (b), (Gdo, 5Dyo
,a)o,+a(Feo,5coo,t)o,ax
-(c), (Gdo, 5sBio, +s)o, za(
Feo, 5aCoo, +z)o-yc= (d), (
DFo, 5Bio, 1) o, zs (Feo-acoo-
z) o, ys ... (e) (Gdo, yTbo
-3) o, z < (Feo, 5sCoo, os) o, ya
-(r).

An important issue for magneto-optical recording media is that a small amount of energy is required during recording, while a large Sin must be obtained during reproduction. Energy during recording is largely determined by the Curie temperature of the magnetic film, film thickness, and thermal conductivity of the medium. FIG. 1 is a graph showing the relationship between film thickness and energy (laser output) required for recording. As is clear from this figure, the film thickness and laser output are linearly proportional to the increase in film thickness up to a film thickness of 20OA (0.02μ country). Film thickness 200A (0,
02μl11) or less, the laser output increases. This is because the laser light is transmitted and no heat is accumulated. Therefore, in the present invention, the thickness of the magnetic thin layer is set to 200 mm.
-1000 A is appropriate.

Further, FIG. 2 is a graph showing the relationship between the alloy composition used in the magnetic thin layer of the present invention, the recordable output (laser power mW), and the Curie temperature (° C.).

In the graph, the solid line shows the laser power and the dotted line shows the Curie temperature. The recording conditions were an LD wavelength of 800 nn+.

A laser pulse width of 5 μs, an external magnetic field of 2000e, and a film thickness of 200A-100OA are used. D with low Curie temperature
As the amount of Y increases, the Curie temperature decreases and the laser power output required for recording decreases.

The structure of the magneto-optical recording medium of the present invention will be explained below with reference to the drawings.

FIG. 3(A) is a schematic diagram showing an example of the layer structure of the magneto-optical recording medium of the present invention, in which a high refractive index layer of 3°, a magnetic thin layer 2 and an anti-oxidation layer 4 are sequentially provided on a substrate l. It is. FIG. 3(B) is a schematic diagram showing another example of layer structure, in which a magnetic thin layer 2, a high refractive index layer 3, a reflective layer 5, and an anti-oxidation layer 6 are sequentially provided on a substrate l. .

The magnetic thin layer 2 may be a single layer or a laminated layer.

As the substrate, glass, plastic, etc. can be used.

The high refractive index layer is, for example, Fe2O3, TiO2, CeO2,
A material having a refractive index of 2.0 or more, such as 5bzOs, WO, Sin, Bi2O3, or CdO, is deposited by a sputtering method.

As the antioxidant layer, MgO, AQ203.5i02, T
Oxides of iO2 and ThO□ are used, and the film thickness is 1
00OA or more.

In FIG. 3(B), a magnetic thin layer is deposited on the substrate to a thickness of 200 to 500 layers, through which laser light during reproduction can pass.

As a reflective layer, a metal thin film Cu, Ag, C1. ^Q,
Rh, Au, Ni, etc. are used. gold p on reflective layer
When using the A thin film, an anti-oxidation layer is required on top of it.

Next, a manufacturing example of the magneto-optical recording medium of the present invention will be specifically explained.

First, a magnetic layer was deposited on a glass substrate with a thickness of 300 ml under an argon gas pressure of 3×10” Torr and a discharge force of 300 ml.
! , and the film production rate was 20 A/sec. Sputtering is performed by rotating the substrate using three targets. For example, the Gd, Tb, and Co magnetic layers are arranged on the Fe target in an area ratio corresponding to that of the magnetic layers. One target is a high refractive index layer, for example SiO, and the other target is provided with an antioxidant layer, for example MgO.

For each laminated film, a shutter on the target is opened and closed in the same vacuum, and the films are sequentially laminated to produce a magneto-optical recording medium.

An example of the structure of the magneto-optical recording medium of the present invention produced as described above is shown in Table 1 below. In the column of magnetic thin layers, (I), (It), (c), (d), (e) and (f) correspond to the alloy compositions exemplified above, respectively. For the magneto-optical recording medium of the present invention shown in Table 1, the Kerr rotation angle (θk) and Faraday rotation angle θ measured using a laser (wavelength 800 nm and intensity 1+sW at the medium surface) and recording frequency 2Mb/ The recording laser power in S is shown in Table 2 below.

Table 1 A. Structure of magneto-optical recording medium [Fig. 3 (A)]-6 (1) 650 people Si0 00A MgO 000A B. Structure of magneto-optical recording medium [Fig. 3 (B)] Vertical position
High refractive index layer B-1 (i) Film thickness 200A Ti0z film thickness 3000A Ag5000T
i023000AB-2(b)n 200ASiO
n 500AAu If TaN3000AB-
3(c)n 200ASiOn 2000ACu
rl Ce023000AB-4(d) It
250A CeO2It 100OA Ali
n CrN 3000AB-5(e) 71 200
ASiO) n 900AAQ 71 Ti0
21000AB-6(1)'+200ASiOI
t 2500ACu” 5iOz5000A table
2 O3 due to Kerr effect (for sample ^) and θF due to Faraday effect (for sample B) Accomplished N - Shun 1 Gen - Recording laser power A-10,587mW ^-2 0.52 8A-3
0,627 A-40,646 A-50,06) 5 A-60,746 B-10,682,5 B-20,602,8 B-30,742,8 B-40,722,5 B- 50,702,3 B-60,883°5 Table 2 shows that the magneto-optical recording medium according to the present invention exhibits a sufficiently large Kerr rotation angle or Faraday rotation angle, and the laser power during recording can also be reduced.

Furthermore, the magneto-optical recording medium according to the present invention can be applied to both an optical modulation method and a magnetic field modulation method, and can also be applied to an overwrite type recording method.

[Brief explanation of the drawings] Figure X is a graph showing the relationship between the film thickness of the magnetic thin layer and recording energy, and Figure 2 is a graph showing the relationship between the alloy composition of the magnetic thin layer and recording energy. , and Figure 3 (
A) and (B) are schematic diagrams showing the layer structure of a magneto-optical recording medium. 1...Substrate, 2...Magnetic thin layer %3...High refractive index layer, 4.6...Antioxidation layer, 5...Reflection layer.

Claims (2)

[Claims] (1) It has a structure in which a high refractive index layer, a magnetic thin layer, and an anti-oxidation layer are sequentially provided on a substrate, and the magnetic thin layer has a general formula (MI_xMII_1_-_x)_z(Fe_yCo_
1_-_y)_1_-_z (where M I is Tb, Gd
or Dy, and MII is Tb, Gd, Dy or B
i, M I and MII are different, and 0.0<x
<1.0, 0.7≦1<1.0 and 0.1<z<0.
It is 3. ) A magneto-optical recording medium comprising at least one kind of magnetic alloy film represented by: (2) It has a structure in which a magnetic thin layer, a high refractive index layer, a reflective layer, and an anti-oxidation layer are sequentially provided on a substrate, and the magnetic thin layer has a general formula (MI_xMII_1_-_x)_z(Fe_yCo_
1_-_y)_1_-_z (where M I is Tb, Gd
or Dy, and MII is Tb, Gd, Dy or B
i, M I and MII are different, and 0.0<x
<1.0, 0.7≦y<1.0 and 0.1<z<0.
It is 3. ) A magneto-optical recording medium comprising at least one kind of magnetic alloy film represented by: