JPH03230340A - 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 [Industrial Field of Application] The present invention relates to a magneto-optical recording medium, and particularly to a magneto-optical recording medium that allows overwriting.

[Prior Art] Conventionally, magneto-optical recording media are known as erasable optical disk memories. Magneto-optical disks have the feature of being able to perform non-contact recording and reproducing at a higher recording density than conventional magnetic recording media using magnetic heads, but they require a process of erasing the recorded portion once beforehand.

A method that eliminates the above drawbacks and enables override by providing a simple magnetic field generator with a constant magnetic field direction in a conventional magneto-optical recording/reproducing device and modulating the intensity of the irradiated laser light is proposed in the International Journal of Optical Memory Research. Symposium report (1)
987): Journal of the Japanese Society of Applied Physics, Volume 26 (1987)
Supplement 26-4J (Proc.

Int, Symp, on 0ptical MeI
Lory, 1987: Jpn, J.

^pp1. Phys, Vol, 26 (19
87) Supplew+ent 26-4). This method will be explained below with reference to FIGS. 1 and 2.

In FIG. 1, a recording medium (1) is composed of a transparent substrate (2), a first magnetic layer (3), and a second magnetic layer (4), each of which is made of ferrimagnetic material such as TbFe or TbFeCo. It will be done. The first magnetic layer (3) and the second magnetic layer (4)
), and information is recorded in the first magnetic layer (3). In Figure 2, (7) is the first magnetic field generator, (8) is the second magnetic field generator (permanent magnet), and the laser beam (9) is focused by the lens (5) and irradiated onto the magnetic layer. Ru. The first magnetic field generator (7) does not change the magnetic field shape of the recording medium (1) with the laser output during reading, and is involved only when the laser output is used for recording and erasing. In the second magnetic field generating device (8), the magnetic (upper surface) of the second magnetic layer (4) is uniformly aligned regardless of the magnetization state of the first magnetic layer (3). The direction of magnetic field 1 in 3) is set in the recording medium (
1) is configured. Next, override will be explained.

The second magnetic field generator (8) aligns the magnetization direction of the second magnetic layer (4) upward. The output of the laser beam (9) is increased, and when the magnetization reversal temperature of the second magnetic layer (4) of the irradiation section (6) is lower than the first magnetic layer (3), the second magnetic layer (4) is activated by the exchange coupling force. When aligned in the magnetization direction, the magnetization direction of the second magnetic layer (4) is transferred to the first magnetic layer (3), and the first magnetic layer (3)
The magnetization direction is upward. In addition, above the magnetization reversal temperature of the second magnetic layer (4), the first magnetization generator (7) causes the magnetization direction of the second r:tPL layer (4) to be directed downward, and furthermore, the magnetization direction of the second r:tPL layer (4) is directed downward. The magnetization direction is transferred to the first magnetic layer (3), and the magnetization direction of the first magnetic layer (3) becomes downward.

In this way, by simply changing the output of the laser beam (9), the first
The magnetization state of the magnetic layer (3) can be changed, allowing direct overwriting.

JP-A-62-137753 discloses a magneto-optical recording medium that is a multilayer thin film of a rare earth to transition metal alloy in which two adjacent layers have different composition ratios of rare earth metal and 3-transfer metal. Further, the same composition as the TbFeCo ternary amorphous magnetic alloy layer used for the first magnetic layer is described as a preferable composition. This is uniform over a large surface and shows improvement in durability.There is no direct override function, and it is said that the thickness of each layer is preferably 100 Å or less.

[Problems to be Solved by the Invention] The conventional magneto-optical recording medium as described above is capable of efficiently overriding optical modulation by providing a magneto-optical recording device with an initialization magnet of a practical magnetic field strength. It was difficult to obtain.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a magneto-optical recording medium capable of overriding optical modulation with a small initializing magnetic field strength.

[Means for Solving the Problems] A magneto-optical recording medium according to the present invention has an axis of easy magnetization perpendicular to the film surface, and is made of TbFeC represented by the general formula Tbx (Fe, -CoY)1-X
o A ternary amorphous magnetic alloy layer and an axis of easy magnetization perpendicular to the film surface, with the general formula (GdxDS'+-x)y(F
CdDyFeCo denoted by e1-zCoz)+-z
A quaternary amorphous alloy layer is laminated on a substrate, and each of the amorphous magnetic alloy layers is exchange-coupled, and in the TbFeCo ternary amorphous magnetic alloy layer, 0.15≦X≦0.25. .0
<Y≦0.3° In the GdDyFcCo quaternary amorphous rli alloy layer, 0≦X≦0.5.0.20 (Y≦0.
When 350<Z<0.50, the cdoi sublattice magnetization is dominant.

[Function] In the present invention, by providing a simple external magnetic field generator (permanent magnet) to a conventional magneto-optical recording device, direct overwriting becomes possible.

[Example] Hereinafter, one implementation ρj of the present invention will be described.

The magneto-optical recording medium of this example has an axis of easy magnetization perpendicular to the film surface, and is configured to satisfy the following conditions at room temperature.

IIC-L2>L1+lIw2 Hc2+Hw2<Il+x+ HI, 1L: Initialization magnetic field Hc2 11w2>HllHa: Recording bias magnetic field Troom<Tc+<Tc2 Troom: Room temperature ■, 1=σw/ (LMs14+) i=1.2 (1st, 1st 2 magnetic layers) Hs, tic
, t, TC are the saturation magnetization of the amorphous alloy layer, respectively.
These are coercive force, film thickness, and Curie temperature, and σ- is the domain wall energy between two amorphous magnetic layers. Moreover, 11□ is the exchange coupling force of the first layer at room temperature.

In order to form the magneto-optical recording medium of the present invention, a film is formed by, for example, a sputtering method or a vacuum evaporation method.

The present invention will be explained in detail below using specific examples, but the present invention is not limited thereto.

Specific example 1゜Substrate: 1.2mm thick glass substrate First magnetic layer:
TbFeCo ternary amorphous? T magnetic alloy layer ■b021 (
Feo9Coo1). 7. Membrane J'7: 500 coercive crabs 10kOe Curie temperature 180°C 21st i! Magnetic layer: GdDyFeCo quaternary amorphous magnetic gold layer (Gdo, zDVo7). 25(F(!O,
BCO0,2) 0.75 Film thickness: 1000 coercivity 2.5 kije Curie temperature = 250°C Using the above constituent materials, a recording medium was obtained by sputtering method.

Next, the operation will be explained. In a steady state, the magnetization direction of the second magnetic layer (4) is aligned upward by the second magnetic field generator (8). The temperature of the irradiated part (6) rises due to irradiation with the low power laser beam (9), and at about 150°C, the exchange force of the first magnetic layer (3) becomes larger than the coercive force, and the difference between the exchange force and the coercive force is approximately It will be about 1ktle. At this time, the first magnetic field generator (7) generates approximately 0.5 k (l) in a certain direction.
Since a magnetic field of e is generated, the first magnetic layer (3) changes the magnetization direction of the second magnetic layer (4) due to the exchange force.
), and the magnetization direction of the first magnetic Jl(3) is directed upward. When irradiated with a high-power laser beam (9), the temperature of the irradiated part (6) rises to about 240°C, so the first magnetic layer (3) reaches a temperature higher than the Curie temperature and loses its magnetization.
Since the second magnetic layer (4) is also near the Curie temperature, its coercive force decreases, and its magnetization is reversed by the magnetic field of the first magnetic field generator (7). When the temperature decreases, the magnetization direction of the first magnetic layer (3) becomes downward due to the exchange force with the second magnetic layer (4). Thereafter, the magnetization direction of the second magnetic layer (4) is again turned upward by the second magnetic field generator (8), but the first magnetic layer (4)
The magnetization direction (3) does not change because the coercive force is larger than the exchange coupling force. The above operation enables optical modulation override, and the pit length is 1 to 1 at a linear speed of 6H/sec.
The magnetic field generated by the first magnetic field generator (7) is 0.5 koe, the magnetic field generated by the second magnetic field generator (8) is 3k (le), and the laser power is 15+nW and 5ff1.
111 was used for optical modulation, and a characteristic with an erasure ratio of 25 dB or more was obtained. (Playback at this time) (War was 11.

Specific Example 2 A magneto-optical recording medium was obtained in the same manner as in Specific Example 1, except that the constituent materials shown in Table 1 were used. Here, the same first magnetic layer (3) and second magnetic layer (4) as in Example 1 were used except for the intermediate layer.

Table 1: Good: erasure ratio of 25 dB or more Recording impossible: direct overwriting (override) is not possible) (erasure ratio of 25 dIl or less) The general formula Tb-(Fe, , Co
, t) +- TbFeCo ternary amorphous magnetic alloy layer with an axis of easy magnetization perpendicular to the film surface, mm
Formula (CdXDy1-X)Y(Fe1-ZCoZ)1-z
A GdDyFeCo quaternary amorphous association layer represented by the above structure is formed on top of the substrate, and each of the above amorphous magnetic alloy layers is exchange-coupled. X≦0.25.0<Y≦Q, 3GdDyF
In the eCo quaternary amorphous magnetic alloy layer, 0≦X≦0.
5,0.2×Y≦0.35. O＜Z＜0゜5teGdDy
By making the sublattice magnetization dominant, it becomes possible to override optical modulation by providing an initialization magnet in a conventional magneto-optical recording device.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional magneto-optical recording medium, and FIG. 2 is a perspective view for explaining the operation. (1)...recording medium, (2)...transparent substrate, (3)...
a first magnetic layer; (4) a second magnetic layer; In each figure, the same reference numerals indicate the same or corresponding parts. Agent So Ga Do Terufu 7 figure Yu 2 figure

Claims (1)

[Claims] A TbFeCo ternary amorphous magnetic alloy layer having an axis of easy magnetization perpendicular to the film surface and represented by the general formula Tb_X(Fe_1_-_YCo_Y)_1_-_X; It has an axis of easy magnetization and has the general formula (Cd_X
Dy_1_-_X)_Y(Fe_1_-_ZCo_Z)
A GdDyFeCo quaternary amorphous alloy layer represented by _1_-_Y is laminated on a substrate, and each of the amorphous magnetic alloy layers is exchange-coupled. ≦X≦0.25, 0<Y≦0.3
, in the GdDyFeCo quaternary amorphous magnetic alloy layer, 0≦X≦0.5, 0.20<Y≦0.35, 0<Z<0
．． 5, a magneto-optical recording medium in which GdDy sublattice magnetization is dominant.