JPS6280845A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the function of a guide track even if a flat substrate having no guide tracks is used by providing an oxide region in a pattern shape to a rare earth-transition metal amorphous magnetic film on a substrate and using the same as the guide tracks. CONSTITUTION:The oxide region 13a formed to the pattern shape of the guide tracks is formed to part of a magnetic layer 13 consisting of the vertically magnetized film of a rare earth-transition metal amorphous on the substrate 1. The magnetic effect and reflectivity in the oxide region 13a are different from the magnetic effect and reflectivity in the part where said region is not formed and therefore, said region functions as the guide track. The oxidation thereof is executed by, for example, selectively implanting oxygen ions to the guide track pattern. The guide tracks 15 are spirally formed on a recording medium 17.

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 (Japanese Patent Publication No. 57-20
691). Recording of information on such magneto-optical recording media is carried out by utilizing the property of rapid changes in coercive force at the Curie temperature or compensation temperature of the magnetic material, and specifically, by using laser light modulated with a binary signal. This is done by irradiating and heating a perpendicularly magnetized magnetic thin film 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.

In such a magneto-optical recording medium, in order to realize high-density recording and to write, read, and erase information without error, a guide track is required to guide the irradiation position of the laser beam.

Conventionally, guide tracks have been formed by using optical interference, for example, by providing grooves with a pitch of about 1 to 3 microns and a depth set to a light interference width of 1/4 λ or 1/8 λ.

When providing guide track grooves on a substrate, a plastic substrate on which a 2P method or the like can be applied is superior in terms of cost, mass production, etc., and is often used. However, when a rare earth-transition metal-based amorphous magnetic film is provided on a plastic substrate, a problem arises in that the magnetic film is oxidized by the influence of moisture inside the plastic and moisture that enters through the plastic, resulting in deterioration of magnetic properties.

If a glass substrate is used as the substrate, this stability problem can be solved, but forming guide track grooves on the glass substrate requires a complicated process.

SUMMARY OF THE INVENTION The present invention provides a magneto-optical recording medium that can function as a guide track even when a flat substrate without guide track grooves is used.

The magneto-optical recording medium of the present invention is a magneto-optical recording medium in which a rare earth-transition metal based amorphous magnetic film is provided on a substrate, in which oxidized regions are provided in a pattern on the magnetic film to serve as guide tracks. It is characterized by

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a magneto-optical recording medium of the present invention. A magnetic layer 13 is provided on the substrate 11, and an oxidized region 13a is formed in a part of the magnetic layer 13 to form a guide track 15.

The magnetic layer 15 is made of a perpendicularly magnetized film of an amorphous rare earth-transition metal alloy. Rare earth metals include Tb (terbium), Dy (dysprosium), and Gd (gadolium).
, Sm (samarium), Ha (holmium), and the like. Examples of transition metals include Fe (iron), Co (cobalt), Cu (copper), Ni (nickel), and Cr (chromium). Specific examples of rare earth-transition metal-based amorphous alloys include T b -F e , T
b −F e −G o , T b −F e −
Cu, Tb-Fe-Ni.

T b −F e −Cr, G d −T b
-F e , T b -D y -F 6 , G
Examples include d-Tb-Fe-Co.

The appropriate thickness of the magnetic layer 13 is about 500 to 5,000 layers, and it can be formed by a vapor deposition method, a sputtering method, an ion blasting method, or the like.

The guide track 15 is composed of oxidized regions 13a formed by selectively oxidizing the magnetic layer 13 in the pattern of the guide track to be formed. In the oxidized region 13a, the amorphous rare earth-transition metal alloy, mainly the rare earth metal, is oxidized, and the magneto-optic effect and reflectance are different from those in the non-oxidized region, so that it can function as a guide track. The oxidized region 13a, that is, the guide track is 1, for example, as shown in FIG.
It is formed in a spiral shape.

The guide track 15 has a width of 0.5 to 1.5μ, for example.
, the magnetic layer 13 is formed with a pitch of about 1.5 to 2.5μ. In particular, since rare earth metal elements are easily oxidized, the oxidized regions 13a can be easily formed to form guide tracks. This oxidation can be performed, for example, by selectively implanting oxygen ions into the magnetic layer corresponding to the guide track pattern. As shown in FIG. 4, this selective ion implantation is carried out by forming a magnetic layer 13 on a substrate 11, then providing a mask pattern 21 for guide tracks to be formed thereon, and then implanting oxygen ions. This can be done by

Oxygen ions are selectively implanted into the portions not covered by the mask pattern 21 to form oxidized regions 13a. In the area where oxygen ions were implanted.

Mainly the rare earth elements are oxidized, and the axis of easy magnetization is tilted in-plane to form the guide track 15.

FIG. 2 is a sectional view showing another example of the structure of the magneto-optical recording medium of the present invention, in which a protective film 19 is further provided on the magnetic layer 13 of the recording medium shown in FIG. The protective film 19 is provided to prevent oxygen ions from being released from the magnetic film 13 due to heat after the oxygen ions are implanted into the magnetic layer 13. The protective film 19 is made of Si, N4. A
I N, S i○.

It is made of 5in2 or the like, and can be created by a vapor deposition method, an ion blating method, a sputtering method, or the like. The appropriate thickness of the protective film is about 500 to 5,000 people.

As the substrate 11 of the magneto-optical recording medium, a non-magnetic material such as glass, ceramic, or metal such as aluminum is appropriately used. Further, a new layer of glass,
According to the magneto-optical recording medium of the present invention, the magnetic layer can be selectively oxidized to change the reflectance and Kerr rotation angle of that portion. Since the guide track is formed by using the guide track, it is not necessary to form a guide track groove on the substrate. Therefore, the degree of freedom in selecting the substrate is increased, such as the use of glass having a flat surface, and the substrate can be selected from the viewpoint of improving the stability of the amorphous rare earth-transition metal magnetic film.

Example 1 A T bo,, F eo, s film (thickness: 0.1 μm) was created on a glass substrate by RF sputtering, and a spiral mask pattern made of photoresist was formed to generate 0□1 ion. was injected to form guide tracks with a width of 1 μm and a pitch of 2.5 μm. When we calculated the reflectance R and Kerr rotation angle θk (both at 633 nm) between the ion-implanted and non-ion implanted areas, we found the following large points, and we were able to use this difference to create a guide track. .

Non-ion implanted part: R=42% θ=0, 20d
eg ion implantation part: R=37% θ1 (=Odeg Example 2 Amorphous T bIL□ (F e, , s, CoIL□,) was deposited on a glass substrate by the binary magnetronus battering method.
. ,, a film (thickness: 0.1 μm) was created and a spiral mask pattern made of photoresist was formed.
+ ions were implanted to form guide tracks with a width of 1 μI and a pitch of 2.5 μm. Reflectance R and Kerr rotation angle θk (both 633
) in nm, there was a large difference as shown below, and this difference could be used to create a guide track.

Non-ion implanted part: R=41.5% θ=0.34d
eg ion implantation part: R=37% θ=Odeg

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are cross-sectional views showing an example of the structure of the magneto-optical recording medium of the present invention. FIG. 3 is a plan view of a disk-shaped magneto-optical recording medium showing an example of the formation of guide tracks. FIG. 4 is a diagram illustrating a method of forming a guide track. 11... Substrate 13... Magnetic layer 13a... Oxidized region 15... Guide track 17... Magneto-optical recording medium 21... Mask pattern pattern 31

Claims (1)

[Claims] 1. A magneto-optical recording medium comprising a rare earth-transition metal amorphous magnetic film provided on a substrate, characterized in that the magnetic film is provided with oxidized regions in a pattern to serve as guide tracks.