JPH0628726A - Recording method for magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To enable the increase of the Curie temp. of a first magnetic thin film in the state of a single layer and to improve the C/N of the recording medium by using a magnetic thin film having the temp. characteristic curve of a specific effective magnetic anisotropy constant as a third magnetic thin film. CONSTITUTION:This magneto-optical recording medium 10 has magnetic layers 15 constituted by laminating the first magnetic thin film 11 having perpendicular magnetic anisotropy, the second magnetic thin film and the third magnetic thin film 13 held by the first magnetic thin film 11 and the second magnetic thin film 12 on a substrate 14. This third magnetic thin film 13 has the higher effective magnetic anisotropy than the effective magnetic anisotropy of the first magnetic thin film 11 at the temp. Tcross where the temp. characteristic curve of the effective magnetic anisotropy constant of the third magnetic thin film and the temp. characteristic curve of the effective magnetic anisotropy of the first magnetic thin film 11 intersect or above. The increase of the Curie temp. Tcl of the first magnetic thin film 11 in the state of the single layer is, therefore, possible and the C/N of the magneto-optical recording medium 10 is improved by increasing a Kerr rotating angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording method for a magneto-optical recording medium, and more specifically, a magneto-optical recording medium for recording on the magneto-optical recording medium by switching and controlling the heating temperature of the medium by laser beam irradiation. The recording method of.

[0002]

2. Description of the Related Art In a magneto-optical recording method for reading information pits (magnetic domains) by magneto-optical interaction, a magnetization direction of a recording medium having a magnetic thin film made of a perpendicular magnetization film is perpendicular to the film surface. In this case, a so-called initialization for pre-aligning in one direction is performed, and a magnetic domain having perpendicular magnetization in the opposite direction to this magnetization direction is formed by a local heating means such as laser light irradiation. Is recorded.

In such a magneto-optical recording medium, when rewriting the recorded information, prior to the rewriting of the information, a process of erasing the recorded information (corresponding to the above initialization), that is, for erasing is performed. Since it takes time, there is a problem that recording cannot be performed at a high transfer rate. Therefore, various recording methods by overwriting, which do not require such an independent erasing process, so-called overwriting method, have been proposed. Promising methods among the overwrite methods include an external magnetic field modulation method, a two-head method in which an erasing head is provided in addition to a recording head, and heating control of a medium by laser light irradiation or the like is controlled to be switched. There is a method of rewriting only by itself.

The external magnetic field modulation method is, for example, Japanese Patent Publication No. 60-
As disclosed in Japanese Patent No. 48806, a magnetic field having a polarity corresponding to an input digital signal current is applied to an irradiation region of a heating beam on an amorphous ferrimagnetic thin film recording medium having an easy axis of magnetization perpendicular to a film surface. Recording is performed by applying the voltage. However, in order to perform recording at a high transfer rate by such an external magnetic field modulation method, an electromagnet that operates in the MHz order, for example, is required. However, it is difficult to manufacture such an electromagnet, and even if it can be manufactured, the power consumption and the amount of heat generation are large, which is not practical.

Further, in the two-head method, an extra head other than the recording head is required, and the two heads must be set apart from each other, which imposes a heavy burden on the drive system, is economically unfavorable, and is suitable for mass production. It has problems such as not being suitable.

A method of performing rewriting only by switching and controlling the heating temperature of a medium by a laser beam or the like is disclosed in, for example, Japanese Patent Laid-Open No. 2-24801.
In a laminated film in which a magnetic thin film and a second magnetic thin film are sequentially magnetically coupled to each other through a third magnetic thin film and laminated, a reversal of the magnetic moment of the second magnetic thin film at the Curie temperature of the first magnetic thin film or more An attempt is made to record a first heating state in which it is heated to a temperature that does not occur and a second heating state in which it is heated to a temperature above the Curie temperature of the first magnetic thin film and sufficient to reverse the magnetic moment of the second magnetic thin film. It is a method of forming recording magnetization in the thermomagnetic recording medium by modulating the information in accordance with the information signal and cooling from each heating state. In this method, the first heating temperature needs to be sufficiently lower than the temperature at which the magnetic moment of the second magnetic thin film is reversed, and the Curie temperature of the first magnetic thin film is equal to or lower than the temperature in the first heating state. It is necessary to be.

By the way, the magnitude of the read signal is the first
Since the Kerr rotation angle of the magnetic thin film is proportional to the Kerr rotation angle of the first magnetic thin film, the larger Kerr rotation angle is preferable. The Kerr rotation angle of a rare earth-transition metal thin film depends on its Curie temperature, and the higher the Curie temperature, the larger the Kerr rotation angle. For example, see Electronic Information Technology Report vol85 MR85.
-47, P17. Therefore, this method has a problem that the Curie temperature of the first magnetic thin film cannot be increased and thus the Kerr rotation angle cannot be increased and the C / N ratio cannot be increased.

As a method for solving this problem, for example, a reproducing layer having a high Curie temperature as a reproducing layer on the first magnetic thin film, that is, a Kerr rotation angle is large, as disclosed in JP-A-63-48637. In order to increase the Kerr rotation angle or to improve the stability of recording pits as disclosed in JP-A-2-187947, a method of providing a reproducing layer is used to form the first magnetic thin film in a multilayer structure. The method of doing is proposed. However, the method of improving the Kerr rotation angle by forming the first magnetic thin film in a multilayer structure complicates the manufacturing equipment and increases the total thickness of the magnetic thin film.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art. The third magnetic thin film has an effective magnetic anisotropy constant K3 and an effective magnetic anisotropy of the first magnetic thin film. The temperature characteristic curve of the constant K1 intersects at a temperature Tcross at which the reversal of the magnetic moment of the second magnetic thin film does not occur, and
By using the magnetic thin film such that the effective magnetic anisotropy constant K3 of the third magnetic thin film is higher than the effective magnetic anisotropy constant K1 of the first magnetic thin film at the temperature Tcross or higher, the first heating state is changed to the first magnetic thin film. The Curie temperature Tc1 of the first magnetic thin film is set to be rewritable even at a Curie temperature Tc1 of
It is an object of the present invention to provide a magneto-optical recording medium capable of increasing the thickness of a single layer and improving the C / N ratio of the magneto-optical recording medium.

[0010]

SUMMARY OF THE INVENTION A recording method for a magneto-optical recording medium according to the present invention comprises a first magnetic thin film having perpendicular magnetic anisotropy, a second magnetic thin film having perpendicular magnetic anisotropy, and first and second magnetic thin films. A magneto-optical recording medium having a magnetic film layer composed of a third magnetic thin film sandwiched between thin films, wherein the third magnetic thin film has a temperature characteristic curve of its effective magnetic anisotropy constant K3 and the first magnetic thin film. A magneto-optical recording medium having an effective magnetic anisotropy larger than that of the first magnetic thin film above the temperature Tcross at which the temperature characteristic curve of the effective magnetic anisotropy constant K1 intersects is used to record an information signal to be recorded. Accordingly, the first heating state in which the temperature is not lower than the temperature Tcross and is not higher than the temperature T1 at which the reversal of the magnetic moment of the second magnetic thin film does not occur;
The magneto-optical recording medium is heated to a second heating state in which the magnetic moment of the second magnetic thin film is equal to or more than the cross temperature and is sufficient to reverse the magnetic moment of the second magnetic thin film, and the magneto-optical recording medium is cooled from the first heating state or the second heating state. By doing so, the above-mentioned first magnetic thin film is made to follow the magnetization of the second magnetic thin film to form magnetization.

In the present invention, the temperature T1 in the first heating state is
Is Tcross or more and less than the Curie temperature Tc1 of the first magnetic thin film, and the temperature T1 in the first heating state is Tcross or more and less than the Curie temperature Tc1 of the first magnetic thin film. It is preferable that the Curie temperature of the third magnetic film is less than Tc3.

According to the present invention as described above, since the temperature T1 in the first heating state can be set to a temperature lower than the Curie temperature Tc1 of the first magnetic thin film, the Curie temperature Tc1 of the first magnetic thin film is set. The Kerr rotation angle of the first magnetic thin film can be increased and the C / N ratio of the magneto-optical recording medium can be improved.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The recording method of the magneto-optical recording medium according to the present invention will be specifically described below. FIG. 1 is a schematic sectional view showing an example of a magneto-optical recording medium used in the present invention. The magneto-optical recording medium 10 used in the present invention is, for example, a first magnetic thin film 1 on a substrate 14 as shown in FIG.
It has a magnetic film layer 15 in which the first, third magnetic thin film 13 and second magnetic thin film 12 are laminated in this order. That is, the magneto-optical recording medium 10 includes the first magnetic thin film 11 having perpendicular magnetic anisotropy, the second magnetic thin film 12 having perpendicular magnetic anisotropy, the first magnetic thin film 11 and the second magnetic thin film on the substrate 14. It has a magnetic film layer 15 consisting of a third magnetic thin film 13 sandwiched between thin films 12, and this third magnetic thin film 13 has a temperature characteristic curve of its effective magnetic anisotropy constant K3 and the first magnetic thin film 1 described above.
Above the temperature Tcross at which the temperature characteristic curve of the effective magnetic anisotropy constant K1 of 1 intersects, the effective magnetic anisotropy is larger than that of the first magnetic thin film 11.

The magneto-optical recording medium 10 as described above may have an enhance film (protective film), a metal film, etc. in addition to the magnetic film layer 15 composed of the first to third magnetic thin films. For example, the following structure may be used.

That is, when laser light is irradiated from the side of the substrate 14, (A) substrate / enhancement film (protective film) / first magnetic thin film /
Third magnetic thin film / second magnetic thin film (B) substrate / first magnetic thin film / third magnetic thin film / second magnetic thin film / metal film (C) substrate / enhancement film (protective film) / first magnetic thin film /
Third magnetic thin film / second magnetic thin film / metal film (D) substrate / enhancement film (protective film) / first magnetic thin film /
Third magnetic thin film / second magnetic thin film / enhancement film (protective film)
/ A structure such as a metal film can be mentioned.

When the surface opposite to the substrate 14 is irradiated with laser light, (E) substrate / enhancement film (protective film) / second magnetic thin film /
Third magnetic thin film / first magnetic thin film (F) substrate / metal film / second magnetic thin film / third magnetic thin film / first magnetic thin film recording layer (G) substrate / protective film / metal film / second magnetic thin film / second Examples include a structure of 3 magnetic thin film / first magnetic thin film (H) substrate / protective film / metal film / second magnetic thin film / third magnetic thin film / first magnetic thin film / enhancement film (protective film).

Further, it is possible to have a structure in which a protective coat or a protective label for imparting scratch resistance is formed on the outermost layer of these magneto-optical recording media. Next, the substrate, the first to the third, which constitute the magneto-optical recording medium used in the present invention
The magnetic thin film, the enhancement film (protective film), and the metal film will be specifically described.

As the substrate 14, in addition to inorganic materials such as glass and aluminum, acrylic resin, polycarbonate, polymer alloy of polycarbonate and polystyrene, and amorphous ethylene-cyclic olefin as shown in US Pat. No. 4,614,778. Copolymer, for example, a copolymer of ethylene and 1,4,5,8-dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene (tetracyclododecene), ethylene And 2-methyl-1,4,5,8-dimethano-1,2,3,4,4
Copolymer with a, 5,8,8a-octahydronaphthalene (methyltetracyclododecene), ethylene and 2-ethyl-1,4,
5,8-Dimethano-1,2,3,4,4a, 5,8,8a-copolymer with octahydronaphthalene or the like, or poly 4-methyl-1-pentene, epoxy resin, polyether sulfone, Organic materials such as polysulfone and polyetherimide can be used. The thickness of the substrate 14 is not particularly limited, but is usually 0.5 mm to 5 mm, preferably 1 mm to 2 m.
m.

As the first magnetic thin film 11, a magnetic thin film having a large perpendicular magnetic anisotropy is used. An example of such a magnetic thin film is an alloy film of a 3d transition metal and a rare earth element. Specific examples of the 3d transition element include Ti, Cr, Mn, Fe, Co, Ni, and Cu, and Fe and Co are preferable. Further, as the rare earth element, specifically, Gd, Tb, Dy, Ho, Er, Y
b, Lu, La, Ce, Pr, Nd, Pm, Sm, Eu
And preferred are Gd, Tb, Nd and Dy.

A more specific example of the magnetic thin film used for the first magnetic thin film 11 is Tb _x (Fe _y C
o _100-y ) _100-x magnetic thin film. However, x is in the range of 15 <x <30 (atomic ratio), and y is in the range of 0 <y <100 (atomic ratio). Further, in the present invention, in the above general formula, a magnetic thin film using another rare earth element such as Gd, Dy, Nd instead of Tb can be used, and Tb, Gd, Dy, Nd, etc. can be used instead of Tb. It is also possible to use a magnetic thin film using a combination of two or more kinds of the rare earth elements. Further, other transition metals and other elements can be added.

The Curie temperature (Tc1) of the first magnetic thin film 11 used in the present invention can be set higher than the Curie temperature (Tc2) of the second magnetic thin film 12, specifically, 100 to 400 ° C. Is preferably in the range of 150 to 300 ° C., and particularly preferably in the range of 150 to 300 ° C. In addition, the coercive force (Hc1) of the first magnetic thin film 11 at room temperature
Is higher than the coercive force (Hc2) of the second magnetic thin film 12, specifically, 3.0 kOe or more, preferably 10.0 kOe or more.

The thickness of the first magnetic thin film 11 is usually in the range of 100 to 1000Å, preferably in the range of 200 to 500Å.

As the second magnetic thin film 12, a magnetic thin film having a large perpendicular magnetic anisotropy is used. An example of such a magnetic thin film is an alloy film of a 3d transition metal and a rare earth element. Specific examples of the 3d transition element include Ti, Cr, Mn, Fe, Co, Ni, and Cu, and Fe and Co are preferable. Further, as the rare earth element, specifically, Gd, Tb, Dy, Ho, Er, Y
b, Lu, La, Ce, Pr, Nd, Pm, Sm, Eu
And preferred are Gd, Tb, Nd and Dy.

A specific example of the magnetic thin film used for the second magnetic thin film 12 is Tb _x (Fe _y Co).
_100-y ) A magnetic thin film made of _100-x can be mentioned. However,
x is 10 <x <23 (atomic ratio) or x is 25 <x <4
The range is 0 (atomic ratio), and y is in the range 0 <y <100 (atomic ratio). In the present invention, in the above general formula, T
It is also possible to use a magnetic thin film using another rare earth element such as Gd, Dy, Nd instead of b, or to use two or more kinds of rare earth elements such as Tb, Gd, Dy, Nd instead of Tb. It is also possible to use a magnetic thin film. Further, other transition metals and other elements can be added.

The Curie temperature (Tc2) of the second magnetic thin film 12 used in the present invention is preferably in the range of 200 to 500 ° C., particularly preferably 250 to 4
It is preferably in the range of 00 ° C. The coercive force (Hc2) of the second magnetic thin film 12 at room temperature is preferably in the range of 0.5 to 3.0 kOe, and particularly preferably 1.0 to 2.0.
It is desirable to be in the range of 0 kOe.

The thickness of the second magnetic thin film 12 is preferably in the range of 300 to 1500Å, particularly preferably in the range of 400 to 800Å.

The third magnetic thin film 13 has a temperature Tcross at which the temperature characteristic curve of its effective magnetic anisotropy constant K3 and the temperature characteristic curve of the effective magnetic anisotropy constant K1 of the first magnetic thin film 11 cross each other, and A magnetic thin film having an effective magnetic anisotropy larger than that of the first magnetic thin film 11 is used.

An example of such a magnetic thin film is an alloy film of a 3d transition metal and a rare earth element. Here, as the 3d transition element, specifically, for example, Ti, Cr, Mn,
Fe, Co, Ni, Cu can be mentioned, preferably Fe,
It is Co. Further, as the rare earth element, specifically, Gd,
Tb, Dy, Ho, Er, Yb, Lu, La, Ce, P
r, Nd, Pm, Sm and Eu are mentioned, and preferably G
d, Tb, Nd and Dy.

A specific example of the magnetic thin film used for the third magnetic thin film 13 is Tb _x (Fe _y Co).
_100-y ) A magnetic thin film made of _100-x can be mentioned. However,
x is in the range of 25 <x <50 (atomic ratio), and y is 0 <
The range is y <100 (atomic ratio). Further, in the present invention, a magnetic thin film using another rare earth element such as Gd, Dy and Nd in place of Tb in the above general formula may be used, and a rare earth element such as Tb, Gd, Dy and Nd may be used. It is also possible to use magnetic thin films that are used in combination of two or more kinds.
Further, other transition metals and other elements can be added.

The Curie temperature (Tc3) of the third magnetic thin film 13 used in the present invention is preferably in the range of 100 to 500 ° C., particularly preferably 200 to 4
It is preferably in the range of 00 ° C. The coercive force (Hc3) of the third magnetic thin film 13 at room temperature is preferably in the range of 0 to 1.0 kOe, particularly preferably 0 to 0.5 kOe.
It is desirable to be in the range of e.

The thickness of the third magnetic thin film 13 is preferably in the range of 50 to 500 Å, particularly preferably in the range of 100 to 300 Å. In the present invention, as shown in FIG. 2, the temperature characteristic curve of the effective magnetic anisotropy constant K1 of the first magnetic thin film 11 and the temperature characteristic curve of the effective magnetic anisotropy constant K3 of the third magnetic thin film 13 are
The effective magnetic anisotropy constant K of the third magnetic thin film 13 intersects at a temperature at which the reversal of the magnetic moment of the magnetic thin film 12 does not occur.
The temperature Tcross at which the temperature characteristic curve of 3 and the temperature characteristic curve of the effective magnetic anisotropy constant K1 of the first magnetic thin film 11 intersect.
As described above, the Curie temperature Tc3 of the third magnetic thin film 13 has a larger perpendicular magnetic anisotropy than that of the first magnetic thin film 11.
However, a third magnetic thin film 13 having a Curie temperature Tc1 lower than that of the first magnetic thin film 11 is used, or, as shown in FIG. 3, an effective magnetic anisotropy constant K1 of the first magnetic thin film 11 is used.
And the temperature characteristic curve of the effective magnetic anisotropy constant K3 of the third magnetic thin film 13 intersect at a temperature at which the reversal of the magnetic moment of the second magnetic thin film 12 does not occur, and the effective magnetic anisotropy of the third magnetic thin film 13 is effective. Above the temperature Tcross at which the temperature characteristic curve of the magnetic anisotropy constant K3 and the temperature characteristic curve of the effective magnetic anisotropy constant K1 of the first magnetic thin film 11 cross each other, the first magnetic thin film 1
The third magnetic thin film 13 having a perpendicular magnetic anisotropy larger than that of 1 is used. In the present invention, the effective magnetic anisotropy constant K of the third magnetic thin film 13 at a temperature of Tcross or higher is used.
3 and the effective magnetic anisotropy constant K1 of the first magnetic thin film 11 (K3 -K1) has a maximum value of 1.0 x 10 ⁴ erg / cc or more. Is preferably used.

Since the third magnetic thin film 13 has a perpendicular magnetic anisotropy larger than that of the first magnetic thin film 11 at the temperature Tcross or more, the first magnetic thin film 11 has the first perpendicular magnetic anisotropy at a temperature lower than the Curie temperature Tc1 of the first magnetic thin film 11. The magnetization direction of the magnetic thin film 11 can be made the same as the magnetization direction of the second magnetic thin film 12. For this reason,
The Curie temperature Tc1 of the first magnetic thin film 11 can be increased, the Kerr rotation angle can be increased, and the C / C of the magneto-optical recording medium can be increased.
The N ratio can be increased.

The temperature T in the first heating state during information recording
1 is the third effective magnetic anisotropy constant K3 and the first magnetic thin film 11
It is preferable that the temperature is such that the difference (K3-K1) from the effective magnetic anisotropy constant K1 of (1) is maximized.

As an enhance film (protective film), its refraction
If the refractive index is higher than the refractive index of the substrate,
Alternatively, any inorganic material may be used. enhance
As a specific example of the film (protective film), TiO 2₂, SiO, T
iO, ZnO, ZrO₂, Ta ₂O_Five, Nb₂O_Five, CeO₂
 , SnO₂ , TeO₂ Oxides such as Si₃N_Four, SiN
x (0 <X ≦ 4/3) nitride such as AlN or BN, Zn
Sulfides such as S and CdS, ZnSe, SiC, Si, etc.
is there. In addition, a ferrite such as cobalt ferrite
, Garnets represented by Bi-substituted garnets, etc.
The transparent material with the Faraday effect of
You may use it.

As the metal film, for example, an aluminum alloy (Al alloy) or a nickel alloy (Ni alloy) is used. This metal film has a function as a heat conduction film or a reflection film, and is made of, for example, Al.
The system alloy film has a function as a heat conduction film, and the Ni system alloy film has a function as a reflection film.

Next, a method of manufacturing the magneto-optical recording medium used in the present invention will be described. The magneto-optical recording medium used in the present invention can be manufactured, for example, as follows. That is, keep the substrate temperature around room temperature,
A composite target in which chips composed of the respective elements constituting the first to third magnetic thin films of the magneto-optical recording medium are arranged in a predetermined ratio, an alloy target composed of a composition of a predetermined ratio, or a target of each element is combined to a predetermined position. A substrate that has been placed and revolved on its own axis using conventionally known film forming conditions such as a sputtering method, an electron beam evaporation method, or a vacuum co-evaporation method (the substrate may be fixed, but in this case, each target may be fixed). Alternately open and close the upper shutter)
The first to third magnetic thin films of the magneto-optical recording medium can be formed by sequentially depositing a thin film having a predetermined composition on top.

The first to third magnetic thin films as described above can be formed at room temperature, and in order to have an easy axis of magnetization perpendicular to the film surface, it is necessary to perform a heat treatment such as annealing after the formation. Absent.

If necessary, the substrate temperature may be set to 50-6.
The recording layer and the reproducing layer can be formed on the substrate while heating to 00 ° C or cooling to -50 ° C. It is also possible to bias the substrate to a negative potential during sputtering. By doing so, the inert gas ions such as argon accelerated by the electric field are not only the target material but also the first to third ions which are being formed.
Since the magnetic thin film is hit, a magneto-optical recording medium having excellent characteristics may be obtained.

In the present invention, the effective magnetic anisotropy constant K3 of the third magnetic thin film 13 and the effective magnetic anisotropy of the first magnetic thin film 11 are obtained by irradiating the magneto-optical recording medium 10 with laser light as described above. Temperature T at which the temperature characteristic curve of constant K1 intersects
a first heating state in which the temperature is equal to or more than cross and does not cause reversal of the magnetic moment of the second magnetic thin film 12;
The magneto-optical recording medium is heated to the second heating state in which the magnetic moment of the second magnetic thin film 12 is equal to or more than the cross and is heated to the temperature T2 sufficient to reverse the magnetic moment of the second magnetic thin film 12, and the first heating state or the second heating state is changed. Recording magnetization is formed on the magneto-optical recording medium by cooling.

Specifically, this is performed as shown in FIG. 4 or FIG. 4 and 5 schematically show, with arrows, the magnetization states of the first magnetic thin film 11 and the second magnetic thin film 12 in one magnetic domain of the magneto-optical recording medium.

The first magnetic thin film 11 and the second magnetic thin film 12
Corresponds to, for example, “0” and “1” between a state where the mutual magnetization directions are the same as shown in the state A and a state where the mutual magnetization directions are opposite to each other as shown in the state B. By doing so, information is recorded. Recording of this information is performed by applying an external magnetic field and heating to temperature T1 or temperature T2 by laser light irradiation or the like. For example, the effective magnetic anisotropy constant K3 of the third magnetic thin film 13 is obtained by first irradiating the magnetic domain in the state A with laser light and modulating the intensity or irradiation time of this laser light according to the recording signal. And the temperature Tcross at which the temperature characteristic curve of the effective magnetic anisotropy constant K1 of the first magnetic thin film 11 intersects, and the magnetic moment of the second magnetic thin film 12 is heated to a temperature T1 at which inversion does not occur due to an external magnetic field. As shown in FIG. 4, when the heating temperature T1 is equal to or higher than Tcross and lower than Tc1, the magnetic energy of the third magnetic thin film 13 becomes larger than that of the first magnetic thin film.
Magnetization in the same direction as that of the magnetic thin film 12 occurs, resulting in state A,
For example, information of "0" is recorded. Also, the heating temperature T1
As shown in FIG. 5, when Tc1 or more, the first magnetic thin film 1
1 loses the magnetization and enters the C state. When this heating is completed and the temperature of the magnetic thin film falls to Tc1, the first magnetic thin film 11 is magnetized in the same direction as the second magnetic thin film 12 due to the exchange coupling force of the second magnetic thin film 12, and becomes the state A. .

On the other hand, the magnetic domain in the state A is set to the above temperature T1.
When heated to a temperature T2 which is higher and is sufficient for reversing the magnetization of the second magnetic thin film 12 by an external magnetic field, the first magnetic thin film 11 loses its magnetization and the state D in which the magnetization of the second magnetic thin film 12 is reversed. Occurs. When this heating is completed and the temperature of the magnetic thin film falls to Tc1, the first magnetic thin film 11 is magnetized in the same direction as the second magnetic thin film 12 by the exchange coupling force of the second magnetic thin film 12, and is in the state E. . An external auxiliary magnetic field is applied to this at about room temperature to reverse the magnetization direction of the second magnetic thin film 12, and the first and second magnetic thin films 11, 1
As a state of B in which the magnetization direction of 2 is opposite, for example, “1”
Record the information of.

In this way, the information of "0" and "1" is recorded by the state A and the state B. In any of the states A and B, overwriting is possible by heating this to the temperature T1 or the temperature T2. That is, regardless of whether the initial state is the state A or the state B, the state A can be obtained by heating to the temperature T1 and the state B can be obtained by heating to the temperature T2. it can.

[0044]

According to the present invention, the temperature characteristic curve of the effective magnetic anisotropy constant K3 of the third magnetic thin film and the temperature characteristic curve of the effective magnetic anisotropy constant K1 of the first magnetic thin film are the same as those of the second magnetic thin film. Since the magnetic thin film that intersects at the temperature Tcross at which the magnetic moment of the thin film does not reverse is used, the temperature of the first heating temperature T1 can be lowered, and thus the Curie temperature Tc1 of the first magnetic thin film can be increased. Therefore, the C / N ratio can be increased without making the first magnetic thin film multi-layered.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a magneto-optical recording medium used in the present invention.

FIG. 2 is a diagram showing temperature characteristic curves of effective magnetic anisotropy constants of a first magnetic thin film and a third magnetic thin film.

FIG. 3 is a diagram showing temperature characteristic curves of effective magnetic anisotropy constants of the first magnetic thin film and the third magnetic thin film.

FIG. 4 is a schematic explanatory view showing a magnetized state of a magnetic thin film.

FIG. 5 is a schematic explanatory view showing a magnetized state of a magnetic thin film.

[Explanation of symbols]

 10 magneto-optical recording medium 11 first magnetic thin film 12 second magnetic thin film 13 third magnetic thin film 14 substrate 15 magnetic film layer

Claims (3)

[Claims] 1. A magnetic comprising a first magnetic thin film having perpendicular magnetic anisotropy, a second magnetic thin film having perpendicular magnetic anisotropy, and a third magnetic thin film sandwiched between first and second magnetic thin films. In a magneto-optical recording medium having a film layer, the third magnetic thin film has a temperature characteristic curve of its effective magnetic anisotropy constant K3 and a temperature characteristic curve of the effective magnetic anisotropy constant K1 of the first magnetic thin film. Above the temperature Tcross at which the magnetic field crosses, a magneto-optical recording medium having an effective magnetic anisotropy larger than that of the first magnetic thin film is used, and the temperature Tcross is increased depending on the information signal to be recorded.
The above is the first heating state in which the magnetic moment of the second magnetic thin film is not reversed, and the temperature T2 is not less than the temperature Tcross and is sufficient to reverse the magnetic moment of the second magnetic thin film. By heating the magneto-optical recording medium to the second heating state in which the first magnetic thin film is cooled to the second heating state, the first magnetic thin film is made to follow the magnetization of the second magnetic thin film by cooling from the first heating state or the second heating state. A recording method for a magneto-optical recording medium, characterized by forming magnetization. 2. The temperature T1 in the first heating state is Tcross.
The recording method for a magneto-optical recording medium according to claim 1, wherein the above is satisfied and the Curie temperature of the first magnetic thin film is less than Tc1. 3. The temperature T1 in the first heating state is Tcross.
The method for recording on a magneto-optical recording medium according to claim 1, wherein the above is satisfied and the Curie temperature of the first magnetic thin film is less than Tc1 and the Curie temperature of the third magnetic film is less than Tc3.