JPH02244441A - Magneto-optical recording medium and magneto-optical recording system - Google Patents

Abstract

PURPOSE:To miniaturize and simplify means for impressing magnetic fields by providing a magnetic film having perpendicular magnetic anisotropy and a spin rearrangeable film on a transparent substrate. CONSTITUTION:The magnetic film 4 having the perpendicular magnetic anisotropy and the spin rearrangeable film 3 are provided on the transparent substrate 1. Since the spin rearrangeable film 3 assists the magnetization inversion of the magnetic film 4, information can be recorded with the small magnetic field. Namely, the magnetic field to be impressed at the time of recording and erasing in optical modulation recording to modulate the intensity of laser light can be made small, the decrease of the number of turns of an electromagnetic coil and driving current for generating the magnetic field and the use of an inexpensive permanent magnet are possible. Contribution is made in this way to the miniaturization, simplification and cost reduction of the magneto- optical recording device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium in which recording is performed by using a laser beam and applying a magnetic field from the outside, and a recording method using the same.

[Conventional technology]

In a magneto-optical recording medium that uses a magnetic film with perpendicular magnetic anisotropy, it is possible to not only record but also erase and re-record in order to make the direction of magnetization of the magnetic film correspond to the information "1" pa 0. .

When recording on a magneto-optical recording medium, thermal energy from a laser beam and a magnetic field are simultaneously applied to the magneto-optical recording medium.

The magnetic field generally requires several hundred oersteds, and an electromagnetic coil or a permanent magnet is used as the magnetic field applying means. However, in order to generate a magnetic field of several hundred Oersteds using an electromagnetic coil, the number of turns in the coil increases and a power source that drives a large current is required, making the magneto-optical recording device larger and more complex. do. Furthermore, when permanent magnets are used, high-performance permanent magnets must be used in order to obtain a strong magnetic field, which is disadvantageous because expensive permanent magnets are used.

Naturally, a larger magnetic field can be obtained by bringing the magnetic field applying means closer to the magneto-optical recording medium. As this type of magnetic field applying means, for example, Japanese Patent Laid-Open No. 63-204532 describes the use of a magnetic head. However, bringing the magnetic field applying means closer to the magneto-optical recording medium reduces the number of turns of the electromagnetic coil and the drive current, contributing to miniaturization and simplification of the magneto-optical recording device. Contact with magnetic field application means, abrasion,
This will cause new problems such as crashes.

Considering these results, in order to miniaturize and simplify the magnetic field application means, and to avoid the constraints of the magnetic head method such as contact or close arrangement of the head and medium, it is necessary to improve the medium configuration. Some kind of ingenuity is required.

From this point of view, for example, Japanese Patent Application Laid-Open No. 63-1520
No. 50 states that a photo-induced magnetic film is provided.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, the photo-induced magnetic film is magnetized in the portion irradiated with the laser beam, and the magnetic flux generated by the magnetic field generating means is concentrated in this portion.

However, such photo-induced magnetism is generally expressed at extremely low temperatures below the temperature of liquid nitrogen, and is not actually effective as a magneto-optical recording medium used near room temperature.

An object of the present invention is to miniaturize and simplify the magnetic field applying means,
Moreover, it is a magneto-optical recording medium that is not subject to restrictions such as contact or close arrangement of the head and medium as in the magnetic head method, and moreover, a magneto-optical recording medium that operates effectively at normal temperatures. Our goal is to provide the following.

[Means to solve the problem]

In order to achieve the above object, the present invention is characterized in that a magnetic film having perpendicular magnetic anisotropy and a spin realignment film are provided on a transparent substrate.

The transparent substrate mentioned above is glass or ultraviolet curing resin.

Polycarbonate (P(:)t polymethyl methacrylate (PMMA), etc.) is used.

As the magnetic film having perpendicular magnetic anisotropy, C0-Cr,
A crystalline alloy such as Fa-Cr or Go-Coo or an amorphous alloy made of a rare earth and a transition metal is used. Here, the rare earths include La, Ca, )'r.

Nd, Pm, Sm, Eu, Gd, Tb, Dy.

The elements are Ho, Er, Tm, Yb, Lu, and Hf, and the transition metals include F' e , G o , N i ,
Sa.

'l'i, V, Cr, Mn, cu, Y, Zr, Nb.

Mo, Ru, Rh, Pd, Ag, Hf, 'l'a, W.

Examples of amorphous alloys made of Re, Os, Ir, Pt, Au, rare earths, and transition metals include Tb-Fe-G
o, Gd-Tb-Fe, Tb-
D y -G o , D y -F
e −G o , N d −T b
-do e -Go, P r-Tb-F e-Go
, Tb-Fe-Go-Nb, Tb
-F e -G o -Cr, G d -F a
-Co-Pt etc. are used.

In addition, as a spin rearrangement film, iron borate Fe5BO
s, rare earth orthoferrite RF a Oa, or rare earth-Co compound R-Go. R here
represents at least one rare earth element selected from the aforementioned rare earth element group.

Magnetic films and spin realignment films can be produced using sputtering, vapor deposition, or CVD (Chemical Vaporl).
aposition method, ion blating method, etc. are used.

In the present invention, it is preferable to utilize a spin rearrangement phenomenon in which the magnetization direction is rotated by 90 degrees.

Applying a laser beam or magnetic field of constant intensity to a magneto-optical recording medium provided with a magnetic film having perpendicular magnetic anisotropy and a spin realignment film, while applying a magnetic field or a laser whose polarity is modulated or whose intensity is modulated. A method of recording by applying light is preferable. [Operation] Spin rearrangement is a phenomenon in which the arrangement state of the magnetic moments (spins) of a magnetic material changes depending on the temperature. In the present invention, the magnetization direction It is preferable to use the spin realignment phenomenon in which the spins rotate by 90". When the laser light is not irradiated or the power of the laser light is weak, the magnetization of the spin realignable film is oriented in the film plane. When irradiated with light and heated above the temperature at which spin rearrangement occurs (spin rearrangement temperature), the magnetization rotates 90 degrees and points in a direction perpendicular to the film surface. At this time, the magnetization can take two orientations, but the magnetic field It follows the direction of the magnetic field generated from the application means, and the required magnetic field is extremely small.

The magnetic field generated from the magnetization of this spin-reordering film.

The magnetic field generated from the magnetic field applying means acts as a bias magnetic field for the magnetic film having superposed magnetic anisotropy.Since the coercive force of the magnetic film is reduced by the irradiation with strong laser light, the direction of the bias magnetic field is Its magnetization is directed towards.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

[Example 1] FIG. 1 shows a magneto-optical recording medium 6 according to the present invention.

On the polycarbonate substrate 1, a silicon nitride film 2, N
d-Go spin rearrangement film 3. 'l'b-Fe-Co-
Nb magnetic! [4, Silicon nitride film 5 is laminated by sputtering.

FIG. 2 shows a method for recording information on the magnetic film 4 of the magneto-optical recording medium 6 having the structure shown in FIG. Laser light 12 emitted from laser light source 7 is turned into a parallel beam by collimating lens 8 , passes through condensing lens 9 , and then enters magneto-optical recording medium 6 .

The incident laser beam 12 is transmitted to the Nd-Go spin realignment film 3.
and T b -F e -G o -N b magnetic ls4 is heated. While the intensity of this laser beam 12 is kept constant, the electromagnetic coil 11 is excited by the magnetic signal 10, and the modulated magnetic field 1
3 is applied to the magneto-optical recording medium 6. The recording principle of this recording method will be described below.

FIG. 3 shows the direction component Ha of the magnetization 14 perpendicular to the back surface with respect to the temperature of the Nd--Go spin realignment film 3 heated by the laser beam 12. When the temperature is below 150°C, the magnetization 14 is oriented in the plane, so M c = O
However, at temperatures above 150° C., the magnetization 14 is oriented perpendicular to the film surface, so Me has a certain value. That is, the spin rearrangement temperature is 150°C.

4 to 8 show N heated by the laser beam 12.
Magnetization 14 and 'I' of d-Go spin realignment film 3
b -F a -G o -N b Magnetization 15 of magnetic film 4
FIG.

As shown in Figure 4, at room temperature,
o-Nb magnetism! lI4 is magnetized so that the magnetization 15 is directed downward *N d -G o spin rearrangement property W
The magnetization 14 of i3 is in-plane. When a laser beam 12 is irradiated and an upward modulating magnetic field 13 is applied as shown in FIG. looks up.

The magnetization 15 of the magnetic film 4 is the same as the magnetization 14 of the spin realignment film 3.
Due to the static magnetic field or magnetic exchange coupling force received from the magnetic field, the magnetization 14 of the spin realigning film 3 is directed in the same direction as the magnetization 14, that is, upward.

As shown in FIG. 6, when the irradiation of the laser beam 12 is completed, the spin reorientation film 3 is cooled below the spin reorientation temperature, its magnetization 14 is again directed in-plane, and the coercive force of the magnetic g4 is
Since it is sufficiently large near a degree, the magnetization of the magnetization reversal region 16 is 1.
5 remains facing upwards. That is, a magnetization reversal region 16 is formed in the magnetic film 4.

As shown in FIG. 7, when the magnetization reversal region 16 is again irradiated with the laser beam 12 and a downward modulating magnetic field 13 is applied, the magnetization 14 of the spin realigning film 3 turns downward, and the magnetization 15 of the magnetic film 4 turns downward. is now downward due to the reasons mentioned above. As shown in FIG. 8, when the irradiation with the laser beam 12 is completed, the magnetization 14 of the spin realigning film 3 is directed in-plane again, and the magnetization 15 of the magnetic film 4 is all directed downward. That is, the magnetization reversal region 16
has disappeared.

Note that instead of the electromagnetic coil 11, a magnetic head or a permanent magnet may be used to apply the magnetic field.

[Embodiment 2] FIG. 9 shows another embodiment of the present invention, in which the magneto-optical recording medium 27 is configured as follows. On the glass substrate 34, an ultraviolet curing resin 17 for forming a guide groove for a light spot is formed to a thickness of about 30 μm.

On top of that, there is an aluminum nitride film 18, G d
-Tb -F" e -Co magnetic film 19 for 800 people,
The Fe5BO* spin realignment film 20 was formed by sputtering by 500 people, and the aluminum nitride film 21 by 1000 people.

[Embodiment 3] FIG. 10 is a configuration diagram of an information recording system using the medium 27 described above.
The motor 30 rotates at a constant rotation speed. The laser beam 23 emitted from the semiconductor laser 22 is turned into parallel light by the collimating lens 24, and then transmitted through the polarizing beam splitter 25 and narrowed down to a diameter of about 1 μm by the focusing lens 26.
is irradiated. A permanent magnet 32 is arranged on the side of the magneto-optical recording medium 27 opposite to the surface on which the laser beam 23 is incident. The laser beam 23 that is incident on the magneto-optical recording medium 27 and reflected is laterally kicked out after being incident on the polarizing beam splitter 25, passes through the analyzer 28, and enters the photodetector 29.

The magnetic film 19 is a ferrimagnetic material as shown in FIG.
The sublattice magnetization 34 of the transition metal. Permanent magnet 32
Since the surface near the magneto-optical recording medium 27 is the north pole, the external magnetic field 33 is applied from the permanent magnet 32 toward the magnetic film 19 .

The semiconductor laser 22 emits light at two intensities, a strong power level 37 and a medium power level 36, during recording. Corresponding to each light emission transient, the spin realignment film 20 is rotated at T in FIG.
s, heated to a temperature of Tx. Now, when the laser beam 23 of medium power level 36 is irradiated onto the magneto-optical recording medium 27, the humidity of the magnetic film 19 in that area increases as shown in FIG.

Since the coercive force is reduced, the net magnetization of the magnetic film is directed in the direction of the external magnetic field 33, thus forming a magnetization reversal region 16. At this time, the temperature of the spin realignment property 1!120 rises only to Tz, and the magnetization remains in the plane-oriented direction, so there is no magnetic coupling force between the magnetic film 19 and the spin realignment film 20. Doesn't work.

On the other hand, a laser beam 23 with a strong power level 37 is applied to the magneto-optical medium 2.
7, as shown in Figure 13.

The spin reorienting film 20 in that part rises to the temperature of the process and generates magnetization in the same direction as the external magnetic field 33. Since this magnetization originally originates from the magnetic moment of F a atoms, it is magnetically coupled to the sublattice magnetization 34 of the transition metal of the magnetic film 19 . Therefore, the net magnetization of the magnetic film 19 is directed downward and in the opposite direction to the direction of the external magnetic field 33. In this way, the magnetization reversal region 16 disappears. That is,
Information can be overridden by the intensity level of the laser light 23.

〔Effect of the invention〕

According to the present invention, since the spin realignment film 3 helps the magnetization reversal of the magnetic film 4, information can be recorded with a small magnetic field. In other words, in so-called optical modulation recording, which modulates the intensity of laser light, it is possible to reduce the applied magnetic field during recording and erasing. Since magnets can be used, it can contribute to miniaturization, simplification, and cost reduction of magneto-optical recording devices. In addition, in so-called magnetic field modulation recording that modulates the magnetic field strength, the magnetic field strength required for modulation can be reduced, so when a magnetic head is used as the magnetic field application means, the magnetic field can be applied at a sufficient distance from the magneto-optical recording medium. Because the heads can be placed apart,
Contact and collision between the head and the medium can be prevented.

[Brief explanation of drawings]

1 and 9 are cross-sectional views of a magneto-optical recording medium according to the present invention, and FIGS. 2 and 10 are schematic diagrams showing a schematic configuration of an apparatus for recording information on a magneto-optical recording medium according to the present invention. , Figure 3 shows the temperature of the spin-reordering film. Explanatory diagrams of magnetization characteristics, Figures 4 to 8 and 1
1 to 13 are explanatory diagrams of recording and erasing operations of the magneto-optical recording medium according to the present invention. 1.34...Substrate, 3,20...Spin realignment film, 4.19...Magnetic film, 6,27...Magneto-optical recording medium, 7...Laser light source, 10...・Information signal, 11・
...Electromagnetic coil, 13...Modulated magnetic field, 14.15...
- Magnetization, 16... Magnetization reversal region, 22... Semiconductor laser, 25... Polarizing beam splitter, 26... Stopping lens. 32... Permanent magnet, 34... Transition metal element, 35
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Claims (1)

[Claims] 1. A magnetic film having perpendicular magnetic anisotropy on a transparent substrate;
1. A magneto-optical recording medium characterized by comprising a spin realignment film. 2. The magneto-optical recording medium according to claim 1, wherein the magnetic film having perpendicular magnetic anisotropy is made of a rare earth element and a transition metal. 3. The magneto-optical recording medium according to claim 1 or 2, wherein the magnetization direction of the spin realigning film is rotated by 90 degrees. 4. Recording is performed by applying a magnetic field whose polarity is modulated while applying laser light of a constant intensity to a magneto-optical recording medium provided with a magnetic film having perpendicular magnetic anisotropy and a spin realignment film. A magneto-optical recording method characterized by: 5. Recording is performed by applying a laser beam whose intensity is modulated while applying a magnetic field of a constant intensity to a magneto-optical recording medium provided with a magnetic film having perpendicular magnetic anisotropy and a spin realignment film. A magneto-optical recording method characterized by: