JPH05347038A - Medium and method for magneto-optical recording - Google Patents

Abstract

PURPOSE:To decrease the initialization magnetic field and the size and cost of a device for overwriting method by modulation of light intensity using a multilayered film recording medium. CONSTITUTION:This recording medium consists of a substrate 1, recording layer 2 and auxiliary layer 3. The recording layer 2 and the auxiliary layer 3 are perpendicularly magnetized films of amorphous alloy essentially comprising rare earth elements and iron group transition metals and have the following magnetic characteritics. Namely, these layers 2, 3 have exchange coupling force, the coercive force is larger in the auxiliary layer 3, the Curie temp. is higher in the auxiliary layer 3, and further, the temp. at which the coercive force of the recording layer 2 is max. is near the Curie temp. of the recording layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct overwritable magneto-optical recording medium and a magneto-optical recording method using the same.

[0002]

2. Description of the Related Art In recent years, magneto-optical recording has been actively developed because it has a larger capacity than conventional magnetic recording and can rewrite information, and some have already been commercially available. .. However, many of the magneto-optical recording devices currently on the market require a step of erasing the original information in advance and then writing new information when rewriting the information, so the erasing operation is time-consuming and time-consuming. It's a loss. Further, various magneto-optical recording methods capable of overwriting have been proposed, but there are many problems and they have not been put to practical use.

The following are known conventional magneto-optical recording methods. General optical modulation method (for example, Journal of Applied Magnetics Vol.8, No.
5 (1984) etc.). Magnetic field modulation method using a fixed magnet (Materials MAG-86-95 (1986) etc. of the Institute of Electrical Engineers of Japan, Magnetics Research Group). Magnetic field modulation method using a flying head (Materials MAG-86-95 (1986) etc. of the Institute of Electrical Engineers of Japan, Magnetics Research Group). Overwrite method using a magnetic head with a resonant circuit and a pulsed laser (IEEE Trans.Magn.24, P.666 (19
88), JP-A-63-37842). Overwrite method by changing the light intensity using a two-layer film (JJ of Appl. Phys., Vol.28 (1989), P367, Y. Mut
oh et. al .: Proc. of the 14th Japan Society for Applied Magnetics (1990) 3
76)

[0004]

Among the above-mentioned conventional magneto-optical recording methods, the optical modulation method generally has a drawback that an erasing operation is required because overwriting cannot be performed and rewriting takes a long time.

Further, in the magnetic field modulation method using a fixed magnet, the magnet needs to have a certain size, resulting in a large power consumption. Further, it is very difficult to increase the speed, and it seems that digital recording of about 1 MHz is the limit.

Further, in the magnetic field modulation method using the floating magnetic head, the magnetic head is brought into contact with the medium almost, and the merit of non-contact of the optical disk is lost. Moreover, it is necessary to use a single plate, and there are problems in terms of storage capacity, substrate warpage, and protection of the magnetic film.

The method using the magnetic head having the resonance circuit and the pulsed laser has the same problem as the above method, although it is better than the above method.

Further, in the overwrite method using the change in light intensity using the two-layer film, the adjustment of the exchange coupling between the two layers is delicate and difficult, a large initialization magnetic field is required, the cost of the initialization magnet is high, and the device is expensive. There is a problem of upsizing.

The present invention has been made in view of the circumstances of the prior art as described above, and has the following objects. (1) In the above method, the initialization magnetic field is reduced. (2) Initialization by a bias magnetic field during recording is possible, and overwriting is possible without using a special initialization magnet. (3) The influence of the degree of exchange coupling between the two layers on the overwrite characteristic is reduced to facilitate the production of the recording medium.

[0010]

To achieve the above object, according to the present invention, two or more magnetic layers made of an amorphous alloy containing a rare earth element and an iron group transition metal as a main component are laminated. At least two layers of them are perpendicular magnetization films, and these two layers are arranged from the first magnetic layer to the second magnetic layer in the direction of incidence of light.
When the magnetic layer is used, the first magnetic layer and the second magnetic layer are exchange-coupled, the coercive force at room temperature is higher in the second magnetic layer, and the Curie temperature is higher than that of the second magnetic layer. And a temperature at which the coercive force of the first magnetic layer is maximized is near the Curie temperature of the first magnetic layer.

Further, according to the present invention, in the above structure, the temperature at which the coercive force of the first magnetic layer is maximum is between the Curie temperature of the first magnetic layer and the Curie temperature of -60 ° C. A magneto-optical recording medium is provided.

Further, according to the present invention, in the above structure, a third magnetic layer for reducing the exchange coupling force acting between the first magnetic layer and the second magnetic layer is provided between the first magnetic layer and the second magnetic layer. A magneto-optical recording medium characterized by the above is provided.

Further, according to the present invention, in the above structure, the third magnetic layer is made of an amorphous alloy containing a rare earth and an iron group transition metal as a main component, and the Curie temperature of the third magnetic layer is the first magnetic body. Provided is a magneto-optical recording medium characterized in that the temperature is higher than the Curie temperature of the layer and the coercive force is maximum near the Curie temperature of the first magnetic layer.

Further, according to the present invention, one of the magneto-optical recording media described above, in which the compensation temperature of the second magnetic layer is below room temperature or in which the compensation temperature does not exist, is used.
Before recording, the magnetization of the second magnetic layer is aligned in the same direction by a relatively weak magnetic field, and then a magnetic field weaker than the magnetic field but in the opposite direction is applied while the light intensity or pulse width or dew ratio is different. There is provided a magneto-optical recording method characterized by irradiating two types of laser pulses to perform direct overwrite.

Further, according to the present invention, one of the above magneto-optical recording media having a compensation temperature of the second magnetic layer between room temperature and the Curie temperature is used, and comparison is made before recording. Of two kinds of laser pulses having different light intensities, pulse widths or duty ratios while applying a magnetic field weaker than the magnetic field and having the same direction by a weak magnetic field. There is provided a magneto-optical recording method characterized by performing direct overwrite by irradiating.

Further, according to the present invention, one of the above magneto-optical recording media having a compensation temperature of the second magnetic material layer between room temperature and the Curie temperature is used, and the second magnetic material at room temperature is used. Magneto-optical recording method characterized in that direct overwrite is performed by irradiating two kinds of laser pulses having different light intensities or pulse widths or duty ratios while applying a magnetic field having an intensity such that layer magnetizations are aligned in the same direction. Will be provided.

[0017]

EXAMPLES The magneto-optical recording medium according to the present invention will be described in detail below. FIG. 1 is a cross-sectional view schematically showing the most basic layer structure of a magneto-optical recording medium according to the present invention. The recording layer 2 and the auxiliary layer 3 are laminated on a substrate 1, and a recording / reproducing laser beam is used. Is incident from the substrate 1 side. The recording layer 2 and the auxiliary layer 3 are made of rare earth metals (Dy, Tb, G, respectively).
d, Nd, etc.) and a perpendicular magnetization film made of an amorphous alloy containing iron group transition metals (Fe, Co, Ni) as main components, and an exchange coupling force acts between the two layers 2 and 3. The magnetic characteristics of both layers are as shown in FIGS. As shown in the figure, the magnetic properties of these magnetic films are Hc ₁ > H at coercive forces of the recording layer 2 and the auxiliary layer 3 at Hc ₁ and Hc ₂ and Curie temperature at room temperature (RT), respectively.
c ₂ and when Tc ₁ and Tc ₂ , Tc ₁ <T
It is c ₂ . At room temperature (RT), Hc ₁ is preferably ₁ kOe or more, Hc ₂ is 2 kOe or less, and Tc ₁ is 120 to
It is preferable that the temperature is about 200 ° C. and Tc ₂ is about 180 to 300 ° C. Furthermore, it is preferable that the temperature at which the coercive force Hc ₁ of the recording layer 2 is maximized is near the Curie temperature Tc ₁ . Details if there is compensation temperature Tcomp ₁ to the recording layer 2 whose compensation temperature Tcomp _1, the temperature of the coercive force Hc ₁ is maximized when the compensation temperature Tcomp ₁ does not exist, Tc ₁ -60
It is preferably between 0 ° C and Tc ₁ .

As a combination of materials for the recording layer 2 and the auxiliary layer 3 which satisfy the above conditions, for example, TbFe and TbFe may be used.
bFeCo, TbDyFeCo and TbFeCo, TbD
yFeCo and TbDyFeCo, DyFeCo and TbF
eCo, TbNdFeCo and TbFeCo, TbFe and GdTbFe, TbDyFeCo and GdTbFe, Dy
FeCo and GdTbFe, TbNdFeCo and GdTb
Fe etc. are mentioned.

In the magneto-optical recording medium of the present invention, in order to adjust the exchange coupling force between the recording layer 2 and the auxiliary layer 3 (the interface domain wall energy when the interface domain wall exists between the two layers). You may provide the intermediate layer of. The intermediate layer is preferably composed of an amorphous alloy film containing a rare earth-iron group transition metal as a main component, like the recording layer and the auxiliary layer. Compared with the other two layers, the perpendicular magnetic anisotropy constant and / or the exchange constant are constant. Is small, and the Curie temperature Tc ₃ is the Curie temperature Tc _{1 of the} recording layer 2.
The temperature at which the coercive force Hc ₃ is maximized is the vicinity of the Curie temperature Tc ₁ of the recording layer 2 in detail. Tc ₁ ± 60 ° C.
It is preferable to be located between In this case, there is no particular restriction on the relationship between Tc ₂ and Tc ₃ . In order to reduce the perpendicular magnetic anisotropy, it is preferable to use Gd, Nd or the like as the rare earth metal forming the alloy film. In order to reduce the exchange constant, it is effective to mix a non-magnetic element. Further, the strength of the exchange coupling force acting between the recording layer 2 and the auxiliary layer 3 can be easily adjusted by changing the film thickness of the intermediate layer. The film thickness is 2
About 50 nm is suitable. Examples of materials used for the intermediate layer include GdFe, GdCo, NdFe, and NdC.
o, DyFe, DyCo, TbFeCo, GdTb
Examples include Fe, TbDyFeCo, and the like mixed with a nonmagnetic element.

As the substrate 1, glass, glass provided with a guide track of an ultraviolet curable resin, polycarbonate, polymethylmethacrylate, epoxy resin or the like can be used.

In addition to the layer structure shown in FIG. 1, as shown in FIG. 3, an intermediate layer, a protective layer, a reflective layer,
The dielectric layer, the guide track layer, the protective substrate, etc. may be provided in an appropriate combination, or the third magnetic layer, the fourth magnetic layer, etc. may be provided. Further, two sheets having these structures may be stuck together to form a double-sided recordable medium.

Next, a recording process using the magneto-optical recording medium having the above structure will be described with reference to FIG. In the figure, the arrow in the layer indicates the direction of the sublattice magnetic moment of the transition metal. Initialization magnetic field Hini and recording bias magnetic field Hb are applied
At (RT or Tc ₂ ), the magnetization is applied in the opposite direction when the magnetization of the auxiliary layer 3 is rich in rare earth, and in the same direction in other cases. That is, in the case of FIGS. 2A and 2B and when there is no Tcomp _2, Hini and Hb need to be reversed. Also,
It is necessary to set Hb to a small value so that the magnetization reversal of the auxiliary layer 3 does not occur during the L process. In the figure, the broken line at the boundary between the recording layer 2 and the auxiliary layer 3 indicates that the interface magnetic wall does not exist, and the solid line indicates that the interface magnetic wall exists.

At the time of recording, as shown in FIGS. 4A to 4C, at least the laser power or the pulse width or the duty ratio of the continuous pulse is changed in accordance with the recording signal to irradiate the laser beam. Here, the case of changing the laser power will be described, but the same applies to the case of changing the pulse width or the duty ratio of continuous pulses.

[0024] First, FIG. 2 (a), those media having magnetic properties, ie the compensation temperature Tcomp ₂ of the auxiliary layer 3 is below a room temperature RT or the compensation temperature Tcomp ₂ does not exist, such as (b) The L process (laser irradiation with low power Pa) when used will be described. In this case, the directions of Hini and Hb are opposite. Before recording, the bit in the state of (a) or (d) of FIG.
Hini is applied to align the magnetization direction of the auxiliary layer 3 with the magnetic field direction. Next, in the opposite direction to Hini, a weaker bias magnetic field Hb (50 Oe-
(About 1 kOe) is applied, the temperature of the magnetic film is raised to near Tc ₁ by laser irradiation with low power Pb, and then cooled. By this process, the state of (b) is set as it is because the bias magnetic field Hb is set so as not to reverse the magnetic field of the auxiliary layer 3. In the state of (e), since the exchange coupling force from the auxiliary layer 3 is large, it is in the opposite direction to the recording bias magnetic field Hb, and becomes the state of (c).

Further, the H process using the above medium will be described. In this case as well, before the recording, as shown in FIG.
Hini is applied to the bit of (a) or (d) to align the magnetization direction of the auxiliary layer 3 with the magnetic field direction. Then H
A bias magnetic field Hb weaker than that of ini is applied, and the temperature of the magnetic film is raised to near Tc ₂ or higher by laser irradiation with high power Pa.
Allow to cool. By this process, the states in (b) and (e) are cooled under the bias magnetic field Hb from the state in which the magnetizations of both the recording layer 2 and the auxiliary layer 3 are substantially zero, so that ( After the magnetization of the auxiliary layer 3 has the same direction as the bias magnetic field Hb as shown in (f), the magnetization direction of the recording layer 2 is also aligned with the exchange coupling force of the auxiliary layer 3, and the state (g) is obtained.

The above in FIG. 2 (a), those media having magnetic properties, ie the compensation temperature Tcomp ₂ of the auxiliary layer 3 is below a room temperature RT or the compensation temperature Tcomp ₂ does not exist, such as (b) Although it was used, (c) of FIG.
Even if the medium having the magnetic characteristics as shown in FIG. 7D, that is, the compensation temperature Tcomp ₂ of the auxiliary layer 3 is between the Curie temperature Tc ₂ and the room temperature RT, if Hini and Hb are set in the same direction, the same principle is exceeded. It becomes possible to write. Also, room temperature R
When the coercive force Hc ₂ of the auxiliary layer 3 at T is small, Hini
It is also possible to serve as Hb.

[0027]

According to the inventions of claims 1, 2, 5 and 7,
The following effects can be obtained. In the method described in the related art, there is a mode in which the recording layer (first magnetic layer) faces the direction of the bias magnetic field during recording and a mode in which the recording layer (first magnetic layer) faces the opposite direction. Therefore,
In the opposite direction, the exchange coupling force from the auxiliary layer (second magnetic layer) needs to be larger than the force of the recording layer in the direction of the magnetic field. Therefore, the exchange coupling force between the two layers requires a certain amount of strength. Since this exchange coupling force is further increased at room temperature, a large initialization magnetic field is required. On the other hand, in the inventions of these claims, since the coercive force Hc ₁ of the first magnetic layer is increased during recording, the first magnetic layer is less likely to be affected by the magnetic field.
Even if the exchange coupling force between layers is small, stable overwrite is possible without being affected by the magnetic field. As a result, the initialization mechanism can be downsized or omitted, which leads to downsizing of the device and cost reduction. Further, it is not necessary to finely adjust the exchange coupling force between the two layers, and the medium can be easily manufactured, leading to cost reduction. According to the invention of claim 3, in addition to the above effects, the exchange coupling force between the two layers can be reduced, and the initialization magnetic field can be reduced. According to the invention of claim 4, since the influence of the magnetic field through the third magnetic layer at the time of recording is reduced by interposing the third magnetic layer, the above effect becomes more reliable.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic layer structure of a magneto-optical recording medium according to the present invention.

2A to 2D are diagrams showing magnetic characteristics of a recording layer and an auxiliary layer of the magneto-optical recording medium of FIG.

FIG. 3 is a cross-sectional view showing another layer configuration example of a magneto-optical recording medium that can be used in the present invention.

FIG. 4 is an explanatory diagram of a recording process when the magneto-optical recording medium of FIG. 2 is used.

5A to 5C are diagrams showing an example of a laser irradiation method.

[Explanation of symbols]

 1 substrate 2 recording layer (first magnetic layer) 3 auxiliary layer (second magnetic layer)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Deguchi 1-3-3 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Masaetsu Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Stocks Inside Ricoh Company (72) Inventor Osamu Nonoyama 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh (72) Inventor Genji Tanaka 1-3-3 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh

Claims (7)

[Claims] 1. A magnetic material layer comprising two or more layers of an amorphous alloy containing a rare earth element and an iron group transition metal as a main component, and at least two layers of which are perpendicular magnetization films. When the first magnetic layer and the second magnetic layer are arranged from the incident direction, the first magnetic layer and the second magnetic layer are exchange-coupled, and the coercive force at room temperature is higher in the second magnetic layer. The magneto-optical recording medium is characterized in that the Curie temperature is higher in the second magnetic layer and the temperature at which the coercive force of the first magnetic layer is maximized is near the Curie temperature of the first magnetic layer. 2. The temperature at which the coercive force of the first magnetic layer is maximized is the Curie temperature of the first magnetic layer and the Curie temperature of −60 ° C.
The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is located between the two. 3. A third magnetic layer for reducing the exchange coupling force acting between the first magnetic layer and the second magnetic layer is provided between the first magnetic layer and the second magnetic layer. The magneto-optical recording medium according to. 4. The third magnetic layer is made of an amorphous alloy containing a rare earth element and an iron group transition metal as a main component, and the Curie temperature of the third magnetic layer is higher than the Curie temperature of the first magnetic layer. 4. The magneto-optical recording medium according to claim 3, wherein the temperature at which is maximum is in the vicinity of the Curie temperature of the first magnetic layer. 5. The magneto-optical recording medium according to claim 1, which has a compensation temperature of the second magnetic layer at room temperature or lower or has no compensation temperature, and is used before recording. Magnetization of the second magnetic layer is aligned in the same direction by a relatively weak magnetic field, and then two types of laser pulses having different light intensities or pulse widths or deduy ratios are applied while applying a magnetic field weaker than the magnetic field but in the opposite direction. A magneto-optical recording method comprising irradiating a laser beam to perform direct overwrite. 6. The magneto-optical recording medium according to claim 1, wherein the compensation temperature of the second magnetic layer is between room temperature and the Curie temperature, and it is relatively weak before recording. The magnetization of the second magnetic layer is aligned in the same direction by the magnetic field, and then two types of laser pulses having different light intensities, pulse widths or duty ratios are applied while applying a magnetic field weaker than the magnetic field and having the same direction. A magneto-optical recording method comprising performing direct overwrite. 7. The magneto-optical recording medium according to claim 1, wherein the compensation temperature of the second magnetic layer is between room temperature and the Curie temperature. A magneto-optical recording method characterized in that direct overwrite is performed by irradiating two kinds of laser pulses having different light intensities or pulse widths or duty ratios while applying a magnetic field having such an intensity that magnetizations are aligned in the same direction.