JPS6029996A - magneto-optical record carrier - Google Patents

Abstract

PURPOSE:To obtain an inexpensive recording carrier with a high S/N ratio and an increment of performance exponent by forming successively a thin film of a garnet compound containing Bi, a vertically magnetized metallic magnetic film and a metallic reflective film as well as a transparent nonmagnetic dielectric film when necessary on a transparent substrate. CONSTITUTION:A garnet thin film 2 containing Bi is formed on the upper surface of a transparent substrate 1 by a sputtering or vapor deposition process, etc. A magnetic thin film 3 whose magnetization facilitating axis is vertical to the film surface is formed on the film 2 by the same process. In addition, a metallic reflective film 4 and a nonmagnetic dielectric film 5 of SiO2 or SiO are formed on the film 3 by the same process. The film 3 uses an Mn or Co crystalline magnetic thin film. For the film 2, an amorphous film of about 0.4mum thickness is formed by a sputtering process with a sintered matter (100mm.phi) of a compound (Bi0.7Y2.3Fe5O12) used as a target. Then an amorphous film 3 of Fe58CO22Tb20 is formed with about 0.04mum thickness as the film 3 by a vacuum vapor deposition process. Then an Al film and SiO2 film are formed with about 0.1mum thickness on the film 3 as films 4 and 5 respectively.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to magneto-optical recording in which information is recorded, reproduced, and erased using laser light, and in particular improves the figure of merit and improves S/N.
The present invention relates to a magneto-optical recording carrier with improved ratio.

[Background of snake light]

With the increase in the amount of information and the miniaturization of paper machines, the recording density will tend to increase even further in the future, and magneto-optical recording, which is capable of high-density, large-capacity, arbitrary readout, storage, etc., will become more popular. It has been attracting attention recently. In magneto-optical recording, a magnetic thin film (perpendicular magnetization film) with an axis of easy magnetization perpendicular to the direction of magnetization is used, and by creating reversed magnetic domains at arbitrary positions with a light beam, the direction of magnetization can be matched. Then '1'.

Binary information of 0" is recorded. On the other hand, reading out the binary signal resulting from such inverted pitching is usually carried out using the Polar Kerr effect or the 7 Alladay effect.

Conventionally, as magnetic thin films for magneto-optical recording, perpendicular magnetization thin films such as MnB1-based crystalline negative films, cloth-transition metal-based amorphous thin films, and compound single-crystal thin films represented by garnet have been proposed. . Among them, rare earth-transfer metal-based amorphous thin films are
Since there are no grain boundaries, medium noise is small, and large-area thin films can be easily produced, so it is currently considered the most promising.

However, in the method of ejecting information from these amorphous perpendicularly magnetized thin films by the polar Kerr effect using reflected light, the reproduction signal level (S /N ratio) is low. Therefore, in order to increase the reproduction signal level, a relatively large garnet-based single-crystal PG film with a rotation angle of 7 Arad or a reflective film is combined with a perpendicular magnetic thin film to form a multilayer structure. Attempts are being made to improve the DS/N ratio.

However, in a multilayer film consisting of a garnet single crystal thin layer and an amorphous magnetic thin film, the Kerr rotation angle is increased by about 1.5 times, but the reflectance from the film is lower than that of the amorphous magnetic thin film alone. Since the S/N ratio is reduced by about half, a large increase in the S/N ratio cannot be obtained, and since a single crystal thin film is used, it is expensive and difficult to increase in area. On the other hand, even in the case of a multilayer film in which a reflective film is provided on an amorphous magnetic thin film, the S/N ratio only increases modestly by about 1.2 times.

[Purpose of the invention]

The purpose of the present invention is to have a large figure of merit expressed by θr/α (where θF is the rotation angle of 7 degrees and α is the absorption coefficient e),
A sputtered or vapor-deposited film of a garnet-based compound containing Bi elements with a low coercive force and a high squareness ratio of the magnetization curve is disposed on or below the perpendicular magnetization film, and a metal reflective film and a non-magnetic d By forming a multilayer film with a turtle film, the figure of merit of the magneto-optical recording medium is 71·θK (here R
The object of the present invention is to provide an inexpensive magneto-optical recording carrier that can increase the reflectance and θ represents the Kerr rotation angle and obtain an 8/N ratio that is insufficient for practical use.

[Summary of the invention]

It is well known that magnetic garnet is significantly less transparent to light than ferromagnetic metals and alloys, and has a relatively large Faraday effect. In particular, magnetic garnet containing Bl has a significantly larger figure of merit (θF/α) in the visible to near-infrared wavelength range than that without Bi additives, and has excellent properties as a material for optical application devices.

The present inventors fabricated a magnetic garnet-based material containing Bi, which has excellent properties as a material for optical application devices, by sputtering or vapor deposition to increase the area of υ.
By disposing it on one side of the perpendicularly magnetized metal magnetic thin film, the recorded information can be magnetically transferred and the Kerr effect can be enhanced. A metal reflective film is provided on the other side to prevent this, and at the same time, the reflected light from the reflective film passes through a perpendicular magnetic thin film and a garnet-based thin film, thereby further increasing the Kerr rotation angle. reached. Also, S on the reflective film of this multilayer film or on the garnet-based thin film.
It has also been found that by providing a non-magnetic visiting material such as iO2 or SiO, the oxidation prevention effect or multichamber reflection within the dielectric film can further enhance the deer effect. In the multilayer structure of the present invention, in order to enhance the Kerr effect due to the light reflected by the reflective film after passing through the metal magnetic thin film, and to make the effect of increasing the reflectance of the multilayer film more advantageous, it is necessary to use a perpendicularly magnetized metal magnetic thin film. It is desirable that the thickness of the thin film be at least a thickness that makes it relatively easy to fabricate a continuous homogeneous film, but not more than a thickness that allows laser light to pass through.For this purpose, it is desirable that the film thickness be 80-1500 mm. . In order for the garnet thread film containing MatcBi to accurately magnetically transfer the information recorded on the perpendicularly magnetized metal magnetic thin film, the garnet family must have a small coercive force Ha, a large residual magnetization, and a large squareness ratio. It is desirable that In addition, in order to accurately magnetically transfer the recorded information on the perpendicularly magnetized metal magnetic thin film and to further reduce reproduction noise due to the magneto-optic effect, it is preferable that the sputtered or vapor-deposited film of the garnet-based compound has an amorphous 'X structure. It is desirable that there be.

[Embodiments of the invention]

The present invention will now be described in detail as usual.

FIG. 1 shows a sectional view of a record carrier showing an embodiment of the present invention. A substrate made of transparent glass or synthetic polymer resin (1
A garnet-based thin film (2) containing Bi gold is formed on the upper surface of the garnet-based thin film (2) by sputtering or vapor deposition, and a magnetic thin film (3) whose axis of easy magnetization is perpendicular to the film surface is formed on the upper surface of the garnet-based thin film (2). is formed by sputtering or vapor deposition, and then a metal reflective film (4) and a nonmagnetic dielectric film (5) of SiOx or SiO are formed by the same method. Here, the perpendicular magnetization thin film (3) is a Mn-based or Co-based crystalline magnetic #l film, or an R,E-TM-based amorphous magnetic film, where E is Gd, Tb, and Dyt TM is Fe. , C
o). For example, as a garnet-based thin film (2), the amorphous negative film with a thickness of about 0.4 μm is coated on a cloth with o, yY2.5Fe.
A sOtz compound sintered body (diameter 100 mm) was used as a target to produce a perpendicularly magnetized film using a sputtering method, and then a perpendicularly magnetized film with a thickness of approximately 0.04 μm.
Amorphous replacement (3) of CoHTbxr was produced, and the peCo
An At film of approximately 0.1 μm and a SiChm film were respectively formed as a reflective film (48 nonmagnetic film (5)) on a Tb amorphous 5JL substrate. The figure of merit vTt·θ is about 0.5, and the reproduction S/N ratio is about 50 dB, which is about 10 dB better than the conventional magneto-optical recording medium.

FIG. 2 is a sectional view of a recording carrier showing another embodiment, in which a metal reflective film (4) of At, Ag, Mg, etc. is coated on the top surface of a substrate (fl) made of transparent glass or synthetic polymer resin. An amorphous or crystalline perpendicularly magnetized film (3) is formed on the gold bridge reflective film by a sputtering method or a vapor deposition method.
(i) A sputtered film or vapor deposited film (2) of a gold-containing garnet compound is entirely provided. For example, as the garnet-based thin film (2), a sputtered amorphous film with a thickness of about 0.2 μm is used as Gd2B! The on-duty magnetized film (
3), Fe12Tb211 with a thickness of about 0.03 μm
An amorphous magnetic film is formed by sputtering, and the perpendicularly magnetized film (
5) When a Mg evaporation gland with a thickness of about 0.1 μm is formed on the lower surface, polarized light from the garnet film (2) side) 1 e −N
The amorphous perpendicularly magnetized film (3
The angle of rotation of the plane of polarization caused by passing through the amorphous perpendicular magnetization film (3) and the garnet film (2) is the same as that of the amorphous perpendicular magnetization film. As a result, the reproduction 8/N ratio was improved by about 10 dB, similar to the multilayer film shown in FIG. 1.

FIGS. 3 and 4 are cross-sectional views of a record carrier in which a large amount of information can be recorded and reproduced from both the upper and lower surfaces using the Polar Kerr effect method, and the recording 'G11t is doubled. Third
In the figure, perpendicularly magnetized metal magnetic films (3), (3) are arranged on both the upper and lower surfaces of the reflective film (4), and the metal magnetic films #(3) in the valley are further arranged.
, (3) Bi fabricated by sputtering method on the top surface of (3)
Garnet-containing thin films (2), (2) are formed, and transparent glass or transparent synthetic polymer resin films are disposed on the garnet-based thin films (2), (2), respectively. In addition, in Fig. 4, a non-magnetic dielectric film such as 8jOx or SiO (
5) Form metal reflective films (4), (4) thereon, form perpendicularly magnetized films (3), (3) on the valley reflection film, and further form each of the metal magnetic films (3J , +3) A Bi-containing garnet thin film +2), +2) prepared by sputtering or vapor deposition is formed upward, and the garnet film (2), (
2) A transparent glass or a transparent synthetic polymer resin film is disposed thereon. The record carriers shown in FIGS. 3 and 4 above are essentially the recording media shown in FIGS. 1 and 4 above stacked so that each film layer is symmetrical with respect to the center N film. Therefore, even if there is a resin adhesive layer in the reflective film layer (4) or the nonmagnetic film layer (5) of each central layer, the same effect as described above can be obtained.

FIG. 5 shows that an air layer (6) is formed in the reflective layer or nonmagnetic layer of each central layer of the recording medium produced in FIGS. 3 and 4 above by inserting a spacer around the outer periphery of the substrate. It is characterized in that the leakage magnetic field of one perpendicularly magnetized film does not affect the magnetization state of the other perpendicularly magnetized film.

The multilayer film structure shown in FIG. 5 is particularly effective when a perpendicularly magnetized film having a relatively small coercive force is used as a recording film. In Figure 5, (6) is the nitrogen layer (4), (4) is the reflective film, (3), (3
) is a metallic magnetic film with an easy axis perpendicular to the film, +2), (
2) shows a Bi-containing garnet thin film produced by sputtering or vapor deposition, and (1) and (1) show transparent substrates.

〔Effect of the invention〕

As is clear from the above description, the magneto-optical recording carrier of the present invention essentially consists of a metal reflective film formed on one side of a perpendicularly magnetized film by a sputtering method or an evaporation method.
It is characterized by forming a garnet-based thin film containing It was found that the garnet-based thin film containing J3i with a large J3i emphasizes the Kerr rotation angle, improves the figure of merit VK/θX of the record carrier, and has a remarkable effect on increasing the reproduction S/N ratio. In addition, many of the present invention)
It is clear that in the @ film structure, the same effect can be achieved even if a transparent magnetic film with a large magneto-optic effect is used instead of the 13i-containing garnet film. Further, by heat treating a garnet film formed on a transparent substrate by sputtering or vapor deposition, the characteristics of the garnet film can be optimized.

[Brief explanation of drawings]

1 to 5 are sectional views showing magneto-optical recording carriers in practical examples of the present invention. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... Garnet-based thin film containing Bi, 3... Perpendicular magnetization film, 4... Reflective film, 5... Non-magnetic group, 6th 1st (2) Fig. 4 Continued from page 1 0 Inventor Yuzuru Hosoe Kokubunji City Higashi Koigakubo Research Institute

Claims (1)

[Claims] 1. A sputtered or vapor-deposited film of a garnet-based compound containing Bi is provided on a transparent substrate, and a metal having an axis of easy magnetization in the direction perpendicular to the film surface is formed on the upper surface of the thin film. 1. A magneto-optical recording carrier comprising a magnetic film, a metal reflective layer provided on the upper surface of the metal magnetic layer, and a transparent non-magnetic dielectric film sequentially formed on the reflective film as required. 2. A metal reflective film is provided on a transparent substrate, a metal magnetic layer having an axis of easy magnetization in a direction perpendicular to the film surface is provided on the metal reflective film, and the upper surface of the metal magnetic layer contains Bi. 1. A magneto-optical recording carrier characterized in that a sputtered film or a vapor-deposited film of a garnet-based compound is disposed thereon, and a non-magnetic electrically shielding film is sequentially formed according to the need for peace of mind. 3. A magneto-optical record carrier according to claim 1, characterized in that the record carriers are arranged close to each other or in close contact with each other so that the substrate side of the record carrier is the outermost side. 4. In the magneto-optical recording carrier according to any one of Items 1 to 3 of K11111, the sputtered or vapor-deposited film of the garnet-based compound is predominantly amorphous. Magneto-optical recording carrier with % characteristics.