JPS621153A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a photomagnetic recording medium which prevents the deterioration of a magnetic layer by oxidation corrosion and has stable characteristics and long life by forming a tantalum nitride film as a protective film of an optical recording medium for which the magnetic film consisting of an amorphous rare earth metal-transition metal is used. CONSTITUTION:The magnetic film 13 and protective film 15 are laminated on a substrate 11. The film 13 consists of the amorphous alloy film of the rare earth-transition metal and is formed on the substrate 11 by a sputtering method, vapor deposition method, ion plating method, etc. The more specific film constitution is exemplified by Gd-Fe, Gd-Co and Tb-Ho-Fe. The adequate thickness of the film 13 is about 0.03-0.5mum. The film 15 consists of tantalum nitride and the thickness thereof is preferably 0.1-0.5mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording medium used for document files, floppy disks, hard disks, and the like.

In recent years, magneto-optical recording media have attracted attention, in which information is recorded by writing magnetic domains on a magnetic thin film using the thermal effect of light, and information is read out using the magneto-optic effect. .

Conventionally, the recording layer used in magneto-optical recording media is T.
Thin films made of rare earth-transition metal-based amorphous magnetic materials such as b-Fe alloys are known. Recording of information on such magneto-optical recording media is carried out by utilizing the characteristics of rapid changes in coercive force at the cue temperature or compensation temperature of the magnetic material, and specifically, by using a laser modulated with a binary signal. This is done by irradiating a perpendicularly magnetized magnetic thin film with light and heating it to reverse the direction of magnetization. Further, reproduction is performed by utilizing the difference in the magneto-optical effect of the magnetic film subjected to inversion recording.

The rare earth-transition metal-based amorphous magnetic film exhibits perpendicular magnetic anisotropy, has a large coercive force Hc, and has a Curie temperature Tc.
Since it has a low magneto-optical effect and a large magneto-optic effect, it is suitable as a magneto-optical recording medium.

However, this amorphous film is susceptible to oxidative corrosion because it exhibits activity against oxygen and water.

In particular, when placed in a high humidity environment, the magnetic properties change and eventually the perpendicular magnetic anisotropy is lost, making it unusable as a magneto-optical memory. To overcome this drawback, S i
o,, S i O, A 120. A protective film such as the above is provided on a magnetic thin film.

However, oxide thin films such as SiO□.

It has not been possible to sufficiently prevent oxidative corrosion phenomena due to the influence of free oxygen, and has not necessarily been desirable as a protective film.

The present invention is an amorphous rare earth material with stable properties and long life.
A transition metal-based optical recording medium is provided.

The magneto-optical recording medium of the present invention is characterized in that a protective film made of tantalum nitride is provided on and/or below the rare earth-transition metal based amorphous magnetic film.

The present invention will be explained in more detail below.

FIG. 1 is a sectional view showing an example of the configuration of a magneto-optical recording medium according to the present invention, in which a magnetic film 13 and a protective film 15 are laminated on a substrate 11. As shown in FIG. The magnetic film 13 is made of a rare earth metal-transition metal amorphous alloy film, and is formed on the substrate 11 by sputtering, vapor deposition, ion blating, or the like. Rare earth metals include S m (samarium) and Gd (gadolinium).

Tb (terbium), Dy (dysprosium).

Examples of the transition metal include Ho (holmium), and examples of the transition metal include Fe (iron) and Co (cobalt). Specific film configurations include, for example, Gd-Fe,
Gd-C-o, Tb-Fe, Dy-Fe, aci-'r
b-Fa, Tb-, Dy-Fe.

Tb-Fe-Co, Sm-Tb-Fa, Tb-Ho
-F a etc. are exemplified. The thickness of the magnetic film 13 is 0.0
Approximately 3 to 0.5 μm is appropriate.

The protective film 15 is made of tantalum nitride.

The thickness of the protective film 13 is suitably about 0.05 to 1.0 μm, preferably 0.1 to 0.5 μm. Protective film 1
3 can be formed by a sputtering method, a vapor deposition method, an ion blating method, etc., and the magnetic film 13 and the protective film 15
It is preferable to form the magnetic film and the protective film in the same vacuum chamber without breaking the vacuum so that no impurities are present at the interface between the magnetic film and the protective film. By providing a protective film made of tantalum nitride on the magnetic film, oxidation of the rare earth metal-transition metal amorphous alloy is effectively prevented.

A non-magnetic material is used as the substrate 11, and for example, a transparent substrate or an opaque substrate such as glass, plastic, or ceramic is used.

FIG. 2 shows another embodiment of the present invention, in which a protective film 17 is provided below the magnetic film 13. The film thickness 1 of the protective film, etc. are the same as in the case shown in FIG.

FIG. 3 shows still another embodiment of the present invention, in which the magnetic film 1
Protective films 15 and 17 are provided to sandwich 3. Thereby, the stability of the magnetic film can be further improved.

Furthermore, a heat insulating film or a reflective film can be provided on the magnetic film.

According to the present invention, in an optical recording medium using a magnetic film made of an amorphous rare earth metal-transition metal, by forming a tantalum nitride film as a protective film, deterioration of the magnetic film due to oxidative corrosion can be prevented. Therefore, it is possible to obtain a magneto-optical recording medium with stable characteristics and long life.

Example 2 A T b -Fe-Co film with a thickness of 1000 mm was formed as a magnetic film under the following conditions using a two-dimensional magnetron sputtering apparatus, and then a T b -Fe-Co film with a thickness of 1000 mm was continuously formed on top of this film in the same sputtering chamber. A human TaN film was formed and a magneto-optical recording medium was manufactured.

Tb-Fe-C.

Residual gas pressure: I Xl0-'torrAr gas pressure:
5 XIO””torr target material: F ea, m
sc OO, LGI T b (each 150mmφ,
3+omt) Discharge type crab 400W (F e,,,G o.,,,
), 100W (Tb) Sputtering time: 15m1n Substrate nickel glass substrate rotation speed: 30rpm Residual gas pressure at end: l Xl0-'torrAr gas pressure:
5 Xl0-'torr target material: T a N
(150mmφ, 3mmt) Discharge type crab 400W Sputtering time: 60a+in Substrate rotation speed: 30rpm On the other hand, as a comparative example, a Si film was formed as a protective film on the Tb-Fa-Go film under the same manufacturing conditions as the TaN film. 1
000 people were created. These recording media were left in an environment of 70° C. and 90% RH in order to undergo forced labor, and changes in Kerr Hc with respect to the standing time were examined. Kerr Hc was measured by irradiating a He-Ne laser (λ = 633 na) from the substrate side to obtain Kerr hysteresis.

This result is the 4th! ! Shown in I.

[Brief explanation of drawings]

Figure 1, 21! f and FIG. 3 are cross-sectional views showing an example of the structure of the magneto-optical recording medium of the present invention. FIG. 4 is a graph showing the relationship between the standing time and Kerr coercivity (Kerr He). 11...Substrate 13...Magnetic film 1
5.17...Protective film fly 1 figure 3 curse PfJ2 figure fly 4 figure f4 call (hours)

Claims (1)

[Claims] 1. A magneto-optical recording medium characterized in that a protective film made of tantalum nitride is provided on and/or below a rare earth-transition metal based amorphous magnetic film.