JPH01290143A - Magneto-optical recording medium and magneto-optical recording and reproducing method - Google Patents

Abstract

PURPOSE:To improve recording density by using magneto-optical recording layers having two-layer constitution subjected to exchange bonding. CONSTITUTION:The 1st, 2nd magneto-optical recording layer 31, 32 films subjected to the exchange bonding can be divided to two types when an exchange interaction acts between the two layers 31 and 32. Namely, one thereof is called P type and is the case in which the sub-lattice magnetization of a rare earth metal is dominant with both the 1st layer 31 and the 2nd layer 32 or in which the sub-lattice magnetization of a rare earth is conversely dominant. The other one is called A type and the sub-lattice magnetization of the transition metal is dominant with the 1st layer 31 and the sub-lattice magnetization of the rare earth is dominant with the 2nd layer 32 or vice versa. The specific magnetization curves and the magneto-optical hysteresis loops of the respective layers 31, 32 are obtainable with each of the P type and the A type by controlling the magnetic characteristic charts and film thicknesses of these two layers 31, 32 and the magnetic wall energy between the layers 31 and 32. The many- valued recording is thereby enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium and a magneto-optical recording/reproducing method for recording and reproducing information using this medium.

[Conventional technology]

Original disk memory is considered as a new memory to replace the current magnetic disk memory because it has high density, large capacity, and high speed access. Among these, magneto-optical disks, which use magneto-optical recording media, have attracted the most attention because they are rewritable and have been actively researched and developed in recent years.

Figure 7 is a basic configuration diagram of a conventionally known magneto-optical recording medium. l
A magneto-optical recording layer 3 is formed of a perpendicularly magnetized film having magnetization in a direction perpendicular to the magnetic field. As the magneto-optical recording layer 3, MnB1°MnCuB1. MnTiB1. MnA
lGe, PtCo, etc. crystalline magnetic thin layer, or G
d, Tb, Dy, Ho, am.

Amorphous magnetic thin films obtained as alloys of rare earth elements such as Nd and transition metals such as Fe, Go, and Ni are known.

FIG. 8 shows a cross-sectional view of a magneto-optical recording medium, in which the substrate 1 has a depth of 600-100 OA and a pitch of 16-2.
．． A t-medium structure is also known in which a groove 11 of 5 μm is formed in a thinly wound or concentric shape, and a magneto-optical recording layer 3 is formed on this substrate 1. #11 formed here is used for tracking access of a laser beam used for recording, reproducing, and erasing information on a recording medium.

As shown in the cross-sectional view of the magneto-optical recording medium in t1100,
In order to prevent aging and deterioration of the magneto-optical recording layer 3, a medium configuration in which both sides of the magneto-optical recording #3 are sandwiched between a spacer 2 and a protective layer 4 has also been known.

Irf! to the above conventional magneto-optical recording medium! The information recording corresponds to a binary signal and is performed in a t-type. That is, as shown in the magnetization state diagram of the original magneto-recorder am in FIG. Recording is performed so as to be in the embrace of reversed magnetic domains. For this reason, the recording density has the disadvantage that it is almost limited by the focal spot diameter of the laser beam used for recording and reproduction. There are attempts to improve the
- Unexamined Japanese Patent Publication No. 62-2) 4540, and Taki et al.; Reproduction characteristics of brightening magnetic recording media ° 1985 IEICE Semiconductor and Materials Division National Conference Proceedings pl-44), Figure 11 was used in this attempt. This is a configuration diagram of a recording medium that is inserted into the vagina. As shown in the figure, it is composed of a multilayer recording layer 35 and a spacer layer 25.

[Problem to be solved by the invention]

However, as one of the methods to increase the recording density of the above-mentioned magneto-optical recording medium, attempts have been made to create a medium with a multi-layered recording layer structure, but it is difficult to control the film thickness of each magneto-optical recording layer and the spacer between the recording layers. This has the disadvantage that it must be performed with high precision, and in order to access each recording layer, the depth of focus of the laser beam must be made shallower than the layer spacing, which requires major changes to this lens system. This has the disadvantage that both the recording medium and the recording device become complicated.

The purpose of the present invention is to solve these conventional drawbacks, and to provide a magneto-optical recording medium that has a medium configuration that allows easy film formation, and a multi-purpose recording medium that does not require a special recording device and that can be used in a wide range of applications with simple recording power control. The object of the present invention is to provide a magnetic recording and reproducing method that makes it possible to record data.

[Means to solve the problem]

The magneto-optical recording medium of the present invention and 'yr:! The IFI recording and reproducing method uses a laser to record on a 4ft-#1 gold layer with perpendicular magnetic anisotropy, and reproduces the difference in the polarization state of the reflected laser beam as a signal in a large magnetic recording medium. ,
a transparent substrate, a first magnetic recording layer formed on the transparent base, and a second magnetic recording layer formed on the first original magnetic recording layer; The magneto-optical recording layer has a magneto-optical recording layer whose magnetization direction and the magnetization direction of the second magneto-optic recording layer are parallel and antiparallel to each other.
Apply l field.

Laser power level P at which the magnetization of both the first and second -yt and m-recording layers is reversed by laser beam irradiation!
and a laser power level P1 for reversing the magnetization of either of the ft magnetic recording layers by laser beam irradiation;
Three-level information is recorded using a laser power level Po that does not cause magnetization reversal in both layers of the magnetic recording layer by laser beam irradiation, and three-level information is obtained corresponding to the magnetization direction of the optical recording layer. It is constructed by reproducing the reflected laser beam as a regenerated state t-signal.

〔Example〕

First, the magneto-optical recording medium and recording/reproducing method of the present invention will be explained with reference to the drawings.

FIG. 1 (al) is a cross-sectional view of the basic structure of the magneto-optical recording medium according to the present invention. In FIG. A recording layer 32 is formed thereon.The substrate 1 is made of glass, polymethyl methacrylate (PMMA), polycarbonate, or a transparent resin such as epoxy. A type in which pits are formed is also used.For magneto-optical recording N11, 32, a crystalline magnetic thin film or an alloy thin film of a rare earth and a transition metal is used.Here, Qd, Tl),
Rare earths such as Dy, Ho, Sm, Nd and Fe, C
A rare-earth transition metal alloy thin film consisting of transition metals such as O, Ni, etc. is used. For film formation, F magnetron sputtering is used.
1:' is adopted, and the first and second magneto-optical recording layers are continuously formed without breaking the vacuum. Since the rare earth transition metal alloy thin film is very easily oxidized, in reality, as shown in FIG. These films are also formed continuously in the same apparatus when forming the magneto-optical recording layer.Transparent 8i
Companions of 3N4 are nitrides such as A4N, SiO, 8i02
A dielectric material such as an oxide such as Ta or Os is used.

Since the spacer 2 is also used for amplifying the Kerr rotation angle during reproduction, it is set to a desired thickness.

Next, according to the present invention, ' between the first and second original magnetic recording layers is
5F, exchange interaction will be explained. The rare earth transition metal alloy thin film used here is a ferrimagnetic material, and the magnetic moments of the rare earth and the transition metal are coupled antiparallel to each other, and the apparent magnetization is the difference between the two sublattice magnetizations. When exchange interaction occurs between 2/1, two types of exchange-coupled pigeon membranes can be divided into two types. As shown in the schematic diagram of the magnetization of the magneto-optical recording layer in Figure 2, one of them is called the P type, in which the sublattice magnetization of the transition metal is dominant in both the first and second layers, or the magnetization is reversed. This is the case where rare earth sublattice magnetization is dominant. The other one is called type A, in which the first layer is dominated by transition metal sublattice magnetization, and the second layer is dominated by rare earth sublattice magnetization.
Or vice versa.

In this recombinant two-layer film, by controlling the magnetic characteristic diagram of both layers, the film thickness, and the domain wall energy between both layers,
Magnetization curves and magneto-optic hysteresis loops of each layer as shown in FIG. 3 are obtained for each of the P type and A type. here.

When the applied magnetic field is increased in the positive direction, the smaller one of the magnetization reversal magnetic fields of each layer is t-Hl, and the larger one is total H2. For example, in the case of the P type shown in Figure 3 (aJ), when the applied magnetic field is 0, the magnetization of both layers is 6 points downward, and the magnetic field is H, and after t, the magnetic field is reduced to zero. Then, a state is obtained in which the magnetization of only the first layer is reversed.
When a magnetic field H2 is applied and the magnetic field is reduced to zero after t, both layers become in an upward magnetized state. The exchange-coupled two-layer membrane was designed so that the temperature characteristics of the first layer and H2 were as shown in the temperature characteristic diagram in Figure 4, and Hb was applied as a bias magnetic field.
At a temperature between Tl and T2, one layer undergoes magnetization reversal, and at a temperature equal to or higher than rT2, both layers undergo magnetization reversal. This mechanism is used for multivalue recording.

Next, a recording/reproducing method will be explained. FIG. 5 is a level diagram of a recording signal, and shows that a constant magnetic field of Hb is applied to a magneto-optical recording medium made of a conversion coupling 2# film by a magnetic field generating means using a permanent magnet or an electromagnet. Three levels of laser power (Po=P
□, ``1 e P2 no black.

irradiate in synchronization with Here, the laser power Pl is shown in FIG.
The power that gives a specific temperature between 2/i#
The magnetization of only one layer is reversed. Further, the laser power P2 is the power that gives the laser irradiation section a specific temperature of 7j T 2 or more as shown in FIG.

The laser power of Po=P is at the same level as the laser power used during reproduction, and is at a specific temperature of 7tTt or less as shown in FIG. At this time, no change is given to the magnetization state of the ZJl film. By such three-level laser irradiation, three-level magnetization states can be formed, and three-value recording can be obtained.

The Kerr effect is used for signal reproduction. By forming the first magneto-optical recording layer to be thinner than the laser beam can pass through, the magnetization state and Kerr rotation shown in FIG. 6 correspond to the magnetization directions of the first and second magneto-optical recording layers. As shown in the correspondence diagram with the angle, three levels of Kerr rotation angles are obtained. This level t-
The ternary signal is reproduced by making the determination at the time of reproduction.

Next, a magneto-optical recording medium prepared according to the present invention and its recording and reproducing characteristics will be explained. 800 Ag was replaced on a polycarbonate substrate with a diameter of 1301 by RJ' magnetron sputtering using 98i1N4 as a spacer. Furthermore, 80OA of 8i3N4 was formed as a protective layer. Medium under an applied magnetic field of 400 Oe? Rotates at 11.3 vIec, clocked at 17MH
2, a signal with a pulse width of 100 ns was set. Magnetization reversal of only the GdFe layer occurs in the recording power range of 4 mW to 5 mW, and magnetization reversal of both the GdFe and '1'bF'eC:o layers occurs at recording power of 5 mW or more, and the results are good for each magnetization state. A good playback signal is obtained.

Note that in the above embodiments, a specific medium is explained, and t is
The present invention is not limited to these combinations of media and materials.

〔Effect of the invention〕

As explained above, the present invention uses an exchange-coupled 7T two-layer i:magnetic recording layer to perform ternary recording corresponding to the magnetization direction of both layers, effectively lowering the recording density from the conventional two-layer structure. This has the effect of being 1.5 times better than value recording. Makoto, 3
Since value recording is performed by controlling laser power, conventional recording devices can be used with almost no changes.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the basic structure of the magneto-optical recording medium according to the present invention, FIG. 2 is a schematic diagram showing the ft and jIi recording magnetizations of FIG. 1, and FIG. 3 is a schematic diagram of the magneto-optical recording medium of FIG. A schematic diagram showing the magnetization curve of the recording layer and Gengaku Isoki Kerr hysteresis loop,
FIG. 4 is a temperature characteristic diagram of the reversal magnetic field of the magneto-optical recording layer in FIG. 1, and FIGS. 5 and 6 are a level diagram of a recording signal according to the present invention and a correspondence diagram between the magnetization state and the Kerr 1g1 rotation angle, respectively. , FIG. 7, FIG. 8, FIG. 9, FIG. 10, and FIG. 11 are companion diagrams for explaining the basic configuration of conventionally known magneto-optical recording media and their recording and reproducing methods. be. 1...Substrate, 2...Spacer, 31...First element! l... air recording layer, 32... second magneto-optical recording layer, 4.
...Protection e0 Agent Patent Attorney Susumu Uchihara Figure F Figure 3 Figure 4 Figure 5 (a) Table row θ l / 2 θ 2) 0 (c) Kerr rotation angle 7] / ：Substrate 8 diagram q diagram

Claims (2)

[Claims] (1) In a magneto-optical recording medium that records information on a magnetic thin film with perpendicular magnetic anisotropy using a laser beam and reproduces the difference in the polarization state of the reflected laser beam as a signal, a transparent substrate and a a first magneto-optical recording layer formed on the magneto-optical recording layer, and a second magneto-optical recording layer formed on the first magneto-optical recording layer, the magnetization direction of the first magneto-optical recording layer being A magneto-optical recording medium, characterized in that three-value information is recorded by a combination of magnetization directions of the second magneto-optical recording layer including parallel and antiparallel. (2) a laser power level P_2 that applies a specific bias magnetic field to the magneto-optical recording medium according to claim (1) and reverses the magnetization of both the first and second magneto-optical recording layers by laser beam irradiation; A ternary signal is generated using a laser power level P_1 that causes the magnetization of either one of the magneto-optical recording layers to be reversed by laser light irradiation, and a laser power level P_0 that does not cause the magnetization of either magneto-optical recording layer to be reversed by laser light irradiation. A magneto-optical recording and reproducing method characterized in that information is recorded and the polarization state of three levels of reflected laser light obtained in correspondence with the magnetization directions of both magneto-optical recording layers is reproduced as a signal.