JPH03181040A - 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 enables recording with small laser power and reproduction C/N.
Regarding large magneto-optical recording media.

Conventionally, amorphous magnetic alloy films such as Gd-Co, Gd-Fe, Tb-Fe,
Gd-Tb-Fe, D7-TI+-Fe, etc. have been used, but those with a single magnetic alloy film formed on a substrate have insufficient magneto-optical properties, Kerr or Faraday rotation angles, and are difficult to reproduce during playback. The S/N was low. There are some materials, such as Gd-Tb-Fe, in which the Kerr rotation angle improves when the Curie temperature is raised, but the Kerr rotation angle is still insufficient, and a high Curie temperature requires high laser power during recording. There is.

The present invention was made in view of the above problems, and it was discovered that there is a close relationship between the thickness of the magnetic thin layer and the laser output necessary for recording, and the present invention also includes a reflective layer on one side of the magnetic thin layer. The inventors have discovered that by providing this, regeneration utilizing the Faraday effect can be more efficiently removed, leading to the completion of the present invention.

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 S/N ratio, that is, a large Faraday rotation angle during reproduction.

The magneto-optical recording medium of the present invention has a magnetic thin layer made of a perpendicularly magnetized film of a transition metal-rare earth metal alloy on a substrate, and further has a reflective layer thereon, and has a thickness of the magnetic thin layer. 1
It is characterized by being 50A-25OA.

As the magnetic thin layer in the present invention, the aforementioned binary or ternary rare earth metal-transition metal amorphous alloy thin film (perpendicularly magnetized film) can be used.

More preferable alloy materials include the following quaternary alloys having perpendicular magnetic anisotropy.

(Tbo-5DYo-a) o-z2 (Feo-scoo
, z) o-yg - (a), (ybo・9B10・
+)o・17(Feo・78CO0・22)0・83
°゛°(b〉・(Gdo-sDYo-b')o-rm
(Feo-*Coo, 1) o-nz = (c).

(Gdo-@sB!o-t6) o・1s (Feo, as
Coo, +z)o, yc゛(d).

(Gdo・7Tbo-3)o-z4(Feo・5sCo
o, os) o, ya -(e).

An important issue with magneto-optical recording media is that it requires a small amount of energy during recording, while a large S/N ratio 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 critical point is around the film thickness of 20OA (0.02μ), and as the film thickness increases beyond this point, the film thickness and laser output increase linearly.
Even if it becomes thinner than this, the laser output will increase. This is because if the film thickness is less than 200 mm, the laser light will pass through and heat will not accumulate. Therefore, in the present invention, from the viewpoint of appropriate heat storage in the magnetic thin layer, the thickness of the magnetic thin layer is set near this critical point, that is, +5OA-25OA. Further, with this film thickness, reproduction is performed using the Faraday effect, so in the present invention, a reflective layer is provided in order to perform reproduction efficiently from the reproduction light incident side.

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

FIG. 2 is a schematic diagram showing an example of the layer structure of the magneto-optical recording medium of the present invention, in which a magnetic thin layer 2, a high refractive index layer 3, a reflective layer 4, and an antioxidant layer 5 are sequentially provided on a substrate I. It is something. 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, i'io2, CeO2
,5b2o3.103.5iO1B i 203, Cd
A substance having a refractive index of 2.0 or more, such as O, is deposited by a sputtering method.

As the antioxidant layer, MgO1A11203.5102,
Oxides of TiO2° and The2 are used, and the film thickness is 100 OA or more.

The magnetic thin layer is deposited with a thickness of 150A-25OA.

A material that can be penetrated by laser light during playback.

As a reflective layer, metal thin film Cu, AI, Ct, Afi
, Rh, ^U and Ni, etc. are used. When a metal thin film is used for the reflective layer, an anti-oxidation layer is required on top of the metal thin film.

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

First, a magnetic layer was placed on a glass substrate with a thickness of 1lIIl under an argon gas pressure of 3×lO″″2 Torr and a discharge force of 300.
1. The film is produced at a film production rate of 20 A/set. Sputtering is performed by rotating the substrate using four targets. For example, the Gd, Tb, and Co magnetic layers are arranged on the Fe target in an area ratio corresponding to the magnetic layers. One target is a high refractive index layer, for example SiO, another target is a reflective layer, for example Co, and yet another target is provided with an antioxidant layer, for example SiO□. 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, (a), (b), (c), (d) and (e) correspond to the alloy compositions exemplified above, respectively. Regarding the magneto-optical recording medium of the present invention shown in Table 1, laser (wavelength 800
Table 2 below shows the Faraday rotation angle θ measured using an open beam and an intensity of 1 mW at the medium surface, and the recording laser power at a recording frequency of 2 Mbit.

Table 1 Structure of magneto-optical recording medium [Fig. 2] No, I No, 2 No, 3 No, 4 No, 5 Rate buried star Touya near star Guen star Sodanso star (i) Film thickness 150A TiO2 film thickness 3000A Ag5000A
Ti0z3000A(k) IF 170ASiOn
500AAun TaN300OA(c)
n 200ASiOn 2000ACan
Ce023000A(d) IF 250AC@O
z n 1000AAQ n CrN300
OA(e) #200ASiOn 2500ACo
n sio2soooA Table 2 Sample P&L J upper Ω - Recording laser power 1
0.68 2.52 0.6
0 2.83 0.74
2.84 0.72
2.55 0.88
3.5 Table 2 shows that the magneto-optical recording medium according to the present invention exhibits a sufficiently large Faraday rotation angle, and the laser power during recording can also be reduced.

Note that 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 overwriting type recording method.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the thickness of a magnetic thin layer and recording energy, and FIG. 2 is a schematic diagram showing an example of the layer structure of a magneto-optical recording medium. ! ... Substrate, 2... Magnetic thin layer, 3... High refractive index layer,
4... Reflective layer, 5... Antioxidant layer.

Claims (1)

[Claims] (1) A magnetic thin layer made of a perpendicularly magnetized film of a transition metal-rare earth metal alloy is provided on a substrate, and a reflective layer is further provided on top of the magnetic thin layer, and the film thickness of the magnetic thin layer is 150 Å to 250 Å. Features of magneto-optical recording media.