JPH03260933A - magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain this magneto-optical recording medium of high reliability which can be used for overwriting with one single laser beam by laminating a memory layer composed of a ferromagnetic film and an antiferromagnetic film which indicates intrasurface magnetic anisotropy at room temp. and generates magnetic phase transition at higher temp. than room temp. to show perpendicular magnetic anisotropy. CONSTITUTION:On a transparent supporting body 1 composed of glass, plastics, etc., a protective film 2 is formed, ferromagnetic film 3 (memory layer) indicat ing perpendicular magnetic anisotropy is provided thereon. Antiferromagnetic film 4 indicating intrasurface magnetic anisotropy at room temp. and generating magnetic phase transition at higher temp. than room temp and indicating perpen dicular magnetic anisotropy is provided as an auxiliary layer and a protective film 5 is formed. When the Curie temps. of the ferromagnetic film 3 and auxilia ry layer 4 are denoted as Tc1 and Tc2 respectively, the relation of Tc1<Tc2 is satisfied. Thus, the obtd. magneto-optical recording medium has excellent storage stability and reliability and can be easily designed and used for overwrit ing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overwritable magneto-optical recording medium.

[Problems to be solved by conventional techniques and inventions] In recent years,
As rewritable optical recording media, magneto-optical recording media that utilize the magneto-optical effect have been actively researched and developed, and some have even been put into practical use.

This magneto-optical recording medium has the advantages of large-capacity, high-density recording, non-contact recording and playback, and ease of access, as well as the ability to overwrite (overwrite) documents, video and still image files, and computer memory. It is expected that it will be used for In order to make a magneto-optical recording medium have performance equivalent to or better than that of a magnetic disk, there are several technical issues, and one of the major ones is override technology. Currently proposed override technologies are broadly classified into magnetic field modulation methods and optical modulation methods (multi-beam method, 2M film method, etc.) depending on the recording method.

The magnetic field modulation method is a method in which recording is performed by reversing the polarity of the applied magnetic field depending on the recorded information. In this method, since the magnetic field must be reversed at high speed, it is necessary to use a floating type magnetic head, making it difficult to exchange the medium.

On the other hand, the optical modulation method is a method in which recording is performed by turning on/off or modulating the intensity of the irradiated laser beam depending on the recording information. Among these methods, the multi-heam method is a pseudo-override method that uses two to three laser beams and reverses the direction of the magnetic field every rotation to perform recording and erasing on a track-by-track basis, but the device configuration becomes complicated. , it has drawbacks such as increased cost. In addition, the 2M film method uses a two-layer film as the recording layer of a magneto-optical recording medium, and attempts to achieve overwriting I.
This is disclosed in Publication No. 8, etc. The method described in the publication includes, for example, a memory layer made of TbFe and a TbFeC
.

Using a magneto-optical recording medium with a two-layer recording layer and an auxiliary layer consisting of a gi layer, after initialization, override is achieved by applying an external magnetic field and irradiating a laser beam with a different power. It is.

That is, in this method, prior to recording, the magnetization of the auxiliary layer is aligned in one direction using an initializing magnetic field, and a high-power laser beam is irradiated to raise the medium temperature T such that T>Tc2 (Tc2 is the Curie temperature of the auxiliary layer). The temperature is increased to
Recording is performed by applying a magnetic field (in the opposite direction to the initialization magnetic field) to reverse the magnetization of the auxiliary layer and transferring that magnetization to the memory layer as the medium cools. to set the medium temperature as Tc, < T < TCz
(Tcm is the Curie temperature of the memory layer). Erasing is performed by raising the temperature to a temperature of (Tcm is the Curie temperature of the memory layer) and transferring the magnetization direction of the auxiliary layer to the memory layer.

Therefore, this method has problems such as difficulty in medium design and susceptibility to the influence of external magnetic fields when storing the medium.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a magneto-optical recording medium that is highly reliable, has a simple medium configuration, and can be overridden with a single laser beam.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a memory layer consisting of a ferromagnetic film exhibiting perpendicular magnetic anisotropy, and a memory layer comprising a ferromagnetic film exhibiting perpendicular magnetic anisotropy, and a memory layer comprising a ferromagnetic film exhibiting in-plane magnetic anisotropy at room temperature and causing a magnetic phase transition at a temperature higher than room temperature. It is made of a 2N film laminated with an auxiliary layer consisting of an antiferromagnetic film exhibiting perpendicular magnetic anisotropy, and when the Curie temperature of the memory layer is TCl and the Curie temperature of the auxiliary layer is Tc2, Tc<Tc2. There is provided an optical magnetic recording medium characterized by having a recording layer that satisfies the following relationship.

The present invention will be explained in detail below based on the drawings.

The magneto-optical il of the present invention! The recording medium has a storage layer consisting of a memory layer made of a ferromagnetic film that exhibits perpendicular magnetic anisotropy, and a memory layer that exhibits in-plane magnetic anisotropy at room temperature and undergoes a magnetic phase transition at a temperature higher than room temperature and exhibits perpendicular magnetic anisotropy. It is made by laminating antiferromagnetic films. 1st
The figure shows an example of the configuration of such a magneto-optical recording medium. This recording medium is made of Si3N, 5iO1Si0, etc. on a transparent support 1 made of glass, plastic, ceramics, etc.
Protective film 2 consisting of 2, etc. (film thickness 100 to 5000)
A ferromagnetic film 3 (thickness: 00A to 5000A) exhibiting perpendicular magnetic anisotropy is provided thereon, and a ferromagnetic film 3 (thickness: 00A to 5000A) exhibiting perpendicular magnetic anisotropy is provided thereon. An antiferromagnetic film 4 (thickness: 100 to 100 mm) that exhibits perpendicular magnetic anisotropy due to transition is provided, and Si
3N4. Protective film 5 (made of Sun, 5i02, etc.)
The film thickness is 100A to 5000A).

Each film can be formed by a sputtering method, a vapor deposition method, an ion blating method, or the like. The ferromagnetic film 3 is made of, for example, Tb.
-Fe, Gd-Fe, Dy-Fe, Gd-
Tb-Fe, Tb-Fe-Co.

- Gd-Fe-Co, Dy4e-Go, Tb-Dy-F
A rare earth-transition metal amorphous film such as e-Co, Gd-Tb-Fe-Co, or An-B1. Mn-C
u-B1. It can be constructed from a polycrystalline film of Co spinel ferrite, Ba ferrite, or the like. The antiferromagnetic film 4 can be composed of, for example, an RCo (R=rare earth metal such as Dy or Nd) film. These ferromagnetic film 3 and antiferromagnetic film 4 must have thermomagnetic properties as shown in FIG. In addition, the Curie temperature of the ferromagnetic film 3 is Tc1
, if the Curie temperature of the antiferromagnetic film 4 is Tc2, then Tcm
It is necessary to satisfy the relationship <Tc2.

Note that the layer structure of the magneto-optical recording medium of the present invention is not limited to that shown in FIG. It is also possible to remove the protective film 2.5 as appropriate.

Next, the operation of magneto-optical recording using the magneto-optical recording medium of the present invention will be explained.

First, prior to recording or erasing, the antiferromagnetic film 4 of the magneto-optical recording medium according to the present invention is initialized.

This initialization is performed in a normal medium driving state (at this time, the medium is irradiated with a laser beam at the reproduction power level and the medium temperature is below T11.x) as shown in Fig. 3(a).
This is done by aligning the magnetization of the antiferromagnetic film 4, which is a perpendicularly magnetized film, upward using an initializing magnetic field Hinj (the direction of application is opposite to the external magnetic field Hex) as shown in FIG.

For recording, a high-power laser beam is irradiated onto the area to be recorded to adjust the medium temperature to the Curie temperature TC2 of the antiferromagnetic film 4.
This is done by raising the temperature to near the same level and applying an external magnetic field Hex. Although the magnetization of the area to be recorded is upward in both the ferromagnetic film 3 and the antiferromagnetic film 4 under normal medium driving conditions, the temperature of the ferromagnetic film 3 is raised to near the TCZ by high-power laser beam irradiation. Then the magnetization disappears and the antiferromagnetism If! In J4, the magnetization is small in both directions.

At this time, since the external magnetic field Hex is applied downward, its magnetization is reversed and becomes downward, and this downward magnetization is transferred toward the ferromagnetic film 3 when it reaches near Tel during the cooling process. , will be retained as is.

Recording is performed as described above. In addition, Fig. 3(a)
shows the magnetization state when the temperature is lowered after recording.

Erasing is performed by irradiating the area to be erased with a low-power laser beam to raise the medium temperature near the Curie temperature Tex of the ferromagnetic film 3, and applying an external magnetic field (1ex) in the same direction as during recording. Figure 3(b)).

When the medium temperature approaches Tc□, the magnitude of magnetization of the antiferromagnetic film 4, which has been initialized in advance and faces upward, becomes larger than the magnitude of magnetization of the ferromagnetic film 3, which faces downward (antiferromagnetic film 4 is larger than the external magnetic field Hex), the magnetization of the antiferromagnetic film 4 is transferred to the ferromagnetic film 4, the magnetization of the ferromagnetic film 3 is directed upward, and erasing is performed.

Further, reproduction is performed by irradiating a laser beam with a power such that the medium temperature is below Tc.

When the medium is not being driven, that is, when the medium is being stored, the medium is not irradiated with a laser beam, so the antiferromagnetic film 4 is a magnetic film with in-plane magnetic anisotropy (see Fig. 3). (C)). In this case, the book=7= medium has a horseshoe-shaped magnetization distribution, and the magnetization exists stably and is not easily affected by external magnetic fields, making the magneto-optical recording medium extremely reliable.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the examples illustrated here.

Polycarbonate substrate with group (130nv diameter)
The following films were successively laminated on top of the film in vacuum by RF binary magnetron sputtering to obtain a recording medium.

Protective film: Si, N4 film (1000 people) Ferromagnetic film: Tbo-21 (Feo, 92coO-081
) 0.79 film (800 Å) antiferromagnetic film: DyCo film (
100OA) Protective film: Si3N4 film (1000 people) The Curie temperature TCt of the ferromagnetic film and the Curie temperature TC2 of the antiferromagnetic film were as follows.

Tc1=160°C Tc2=250°C The temperature at which the antiferromagnetic film undergoes a magnetic phase transition from an in-plane magnetic anisotropic film to a perpendicular 8-magnetic anisotropic film was 60'C.

The recording medium obtained as described above was driven at a linear velocity of 10 m/s, the initializing magnetic field n1 = 2KOe, the external magnetic field Hex
= 4000e (in the same direction during recording and erasing), and recording/reproducing the IN)Iz signal by changing the irradiation laser power as shown below during recording, erasing, and reproducing. Characteristics were evaluated.

Laser power near during recording: 6 mL 1 Laser power during erasing: 5.5 m (1 Laser power during playback: 2 mW As a result, the C ratio was 47 dB.Furthermore, the C ratio was 47 dB on the recording medium under the same conditions. When overriding was performed at the recording frequency, a good C/N ratio of 46 dB was obtained.

〔Effect of the invention〕

According to the present invention, by having the above structure, it is possible to provide a magneto-optical recording medium that has excellent storage stability, high reliability, and allows for easy override in medium design.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the layer structure of the magneto-optical recording medium according to the present invention, and FIG. 2 is a diagram showing the temperature characteristics of the coercive force Hc of the ferromagnetic film and antiferromagnetic film of the magneto-optical recording medium of the present invention. , FIG. 3 is a diagram showing the magnetization state at the time of initialization, recording, erasing, and storage. ■...Support 2.5...Protective film 3...Ferromagnetic film (Memory J! Ri 4...Antiferromagnetic film (auxiliary layer) Fig. 1

Claims (1)

[Claims] (1) A memory layer consisting of a ferromagnetic film that exhibits perpendicular magnetic anisotropy, and an antiferromagnet that exhibits in-plane magnetic anisotropy at room temperature and undergoes a magnetic phase transition at temperatures higher than room temperature to exhibit perpendicular magnetic anisotropy. The recording layer is composed of a two-layer film laminated with an auxiliary layer consisting of a film, and satisfies the relationship T_c_1<T_c_2, where the Curie temperature of the memory layer is T_c_1 and the Curie temperature of the auxiliary layer is T_c_2. Features of magneto-optical recording media.